Αρχική ΑΕΠΠ - Δομές Δεδομένων Λειτουργικά Συστήματα Δίκτυα Υπολογιστών ΙΙ Βάσεις Δεδομένων Παιδαγωγικά - Διδακτική

Εισαγωγικά

Εισαγωγή στα Λ.Σ. Βασικές Δομές Η/Υ Βασικές Δομές Λ.Σ

Διεργασίες

Διεργασίες Χρονοπρογραμματισμός Συγχρονισμός

Αδιέξοδα

Μνήμη

Μονοπρογραμματισμός Εναλλαγή Εικονική Μνήμη Κατάτμηση

Είσοδος / Έξοδος

Σύστημα Αρχείων

Διεπαφή Υλοποίηση

 Ιστορικό Πρόσφατες αλλαγές Εκτύπωση Αναζήτηση

Ιστορικό: OS.Introduction

Απόκρυψη μικρών αλλαγών - Αλλαγές κώδικα

26-08-2008 (11:31) από Άρης -
Αλλαγή σειράς 434 από:
  • MULTICS was a time-sharing system created on a large mainframe GE computer (since then taken over by Honeywell), by GE, by Bell Labs, and by faculty at MIT. It was very ?exible, and oriented toward programmers.
σε:
  • MULTICS was a time-sharing system created on a large mainframe GE computer (since then taken over by Honeywell), by GE, by Bell Labs, and by faculty at MIT. It was very flexible, and oriented toward programmers.
Αλλαγή σειρών 528-530 από:
* supervision of the execution of user programs to prevent errors and improper use of the computer, and
* management of the operation and control of I/O devices.
σε:
  • supervision of the execution of user programs to prevent errors and improper use of the computer, and
  • management of the operation and control of I/O devices.
Αλλαγή σειράς 569 από:

'''In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems.

σε:

In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems.

Αλλαγή σειρών 572-573 από:

Explain your answer.'''

σε:

Explain your answer.

22-07-2008 (19:32) από Άρης -
Αλλαγή σειρών 313-314 από:

Question-

σε:

Question

22-07-2008 (16:17) από Άρης -
Αλλαγή σειράς 1 από:
σε:
22-07-2008 (16:16) από Άρης -
Αλλαγή σειράς 1 από:
σε:
Αλλαγή σειρών 537-538 από:

List the four steps that are necessary to run a program on a completely dedicated machine.

σε:

List the four steps that are necessary to run a program on a completely dedicated machine.

Αλλαγή σειρών 555-556 από:

An extreme method of spooling, known as staging a tape, is to read the entire contents of a magnetic tape onto disk before using it. Discuss the main advantage of such a scheme.

σε:

An extreme method of spooling, known as staging a tape, is to read the entire contents of a magnetic tape onto disk before using it. Discuss the main advantage of such a scheme.

Αλλαγή σειράς 569 από:

In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems.

σε:

'''In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems.

Αλλαγή σειρών 572-573 από:

Explain your answer.

σε:

Explain your answer.'''

Αλλαγή σειρών 587-588 από:

What is the main advantage of multiprogramming?

σε:

What is the main advantage of multiprogramming?

Αλλαγή σειρών 601-602 από:

What are the main differences between operating systems for mainframe computers and personal computers?

σε:

What are the main differences between operating systems for mainframe computers and personal computers?

Αλλαγή σειρών 615-616 από:

Define the essential properties of the following types of operating systems: Batch Interactive Time sharing Real time Distributed.

σε:

Define the essential properties of the following types of operating systems: Batch Interactive Time sharing Real time Distributed.

Αλλαγή σειρών 633-634 από:

We have stressed the need for an operating system to make efficient use of the computing hardware. When is it appropriate for the operating system to forsake this principle and to “waste” resources? Why is such a system not really wasteful?

σε:

We have stressed the need for an operating system to make efficient use of the computing hardware. When is it appropriate for the operating system to forsake this principle and to “waste” resources? Why is such a system not really wasteful?

Αλλαγή σειρών 647-648 από:

Under what circumstances would a user be better off using a time-sharing system, rather than a personal computer or single-user workstation?

σε:

Under what circumstances would a user be better off using a time-sharing system, rather than a personal computer or single-user workstation?

Αλλαγή σειρών 661-662 από:

Describe the differences between symmetric and asymmetric multiprocessing. What are three advantages and one disadvantage of multiprocessor systems?

σε:

Describe the differences between symmetric and asymmetric multiprocessing. What are three advantages and one disadvantage of multiprocessor systems?

Αλλαγή σειρών 675-676 από:

Why are distributed systems desirable?

σε:

Why are distributed systems desirable?

Αλλαγή σειρών 689-690 από:

What is the main difficulty that a programmer must overcome in writing an operating system for a real-time environment?

σε:

What is the main difficulty that a programmer must overcome in writing an operating system for a real-time environment?

22-07-2008 (16:14) από Άρης -
Πρόσθεση σειρών 4-5:

Question

Πρόσθεση σειρών 18-19:

Question

Πρόσθεση σειρών 32-33:

Question

Πρόσθεση σειρών 46-47:

Question

Πρόσθεση σειρών 60-61:

Question

Πρόσθεση σειρών 74-75:

Question

Πρόσθεση σειρών 88-89:

Question

Πρόσθεση σειρών 102-103:

Question

Πρόσθεση σειρών 128-129:

Question

Πρόσθεση σειρών 142-143:

Question

Πρόσθεση σειρών 156-157:

Question

Πρόσθεση σειρών 170-171:

Question

Πρόσθεση σειρών 184-185:

Question

Πρόσθεση σειρών 198-199:

Question

Αλλαγή σειρών 210-211 από:

σε:

Question

Πρόσθεση σειρών 226-227:

Question

Πρόσθεση σειρών 240-241:

Question

Πρόσθεση σειρών 255-256:

Question

Πρόσθεση σειρών 270-271:

Question

Πρόσθεση σειρών 284-285:

Question

Πρόσθεση σειρών 299-300:

Question

Αλλαγή σειρών 311-312 από:

σε:

Question-

Πρόσθεση σειρών 327-328:

Question

Πρόσθεση σειρών 341-342:

Question

Πρόσθεση σειρών 355-356:

Question

Πρόσθεση σειρών 369-370:

Question

Αλλαγή σειρών 381-382 από:

σε:

Question

Πρόσθεση σειρών 397-398:

Question

Πρόσθεση σειρών 411-412:

Question

Πρόσθεση σειρών 425-426:

Question

Πρόσθεση σειρών 441-442:

Question

Πρόσθεση σειρών 455-456:

Question

Πρόσθεση σειρών 469-470:

Question

Πρόσθεση σειρών 483-484:

Question

Πρόσθεση σειρών 497-498:

Question

Πρόσθεση σειρών 515-516:

Question

Πρόσθεση σειρών 535-536:

Question

Πρόσθεση σειρών 553-554:

Question

Πρόσθεση σειρών 567-568:

Question

Πρόσθεση σειρών 585-586:

Question

Πρόσθεση σειρών 599-600:

Question

Πρόσθεση σειρών 613-614:

Question

Πρόσθεση σειρών 631-632:

Question

Πρόσθεση σειρών 645-646:

Question

Πρόσθεση σειρών 659-660:

Question

Πρόσθεση σειρών 673-674:

Question

Πρόσθεση σειρών 687-688:

Question

Αλλαγή σειρών 697-700 από:

σε:
22-07-2008 (16:05) από Άρης -
Πρόσθεση σειρών 8-9:

Answer

Πρόσθεση σειρών 20-21:

Answer

Πρόσθεση σειρών 32-33:

Answer

Πρόσθεση σειρών 44-45:

Answer

Πρόσθεση σειρών 56-57:

Answer

Πρόσθεση σειρών 68-69:

Answer

Πρόσθεση σειρών 80-81:

Answer

Αλλαγή σειρών 92-93 από:
σε:

Answer

Πρόσθεση σειρών 116-117:

Answer

Πρόσθεση σειρών 128-129:

Answer

Πρόσθεση σειρών 140-141:

Answer

Πρόσθεση σειρών 152-153:

Answer

Πρόσθεση σειρών 164-165:

Answer

Πρόσθεση σειρών 176-177:

Answer

Πρόσθεση σειρών 188-189:

Answer

Πρόσθεση σειρών 200-201:

Answer

Αλλαγή σειρών 212-213 από:
σε:

Answer

Αλλαγή σειρών 223-226 από:

Answer

σε:

Answer

Πρόσθεση σειρών 238-239:

Answer

Αλλαγή σειρών 248-251 από:

Answer

σε:

Answer

Πρόσθεση σειρών 263-264:

Answer

Πρόσθεση σειρών 275-276:

Answer

Πρόσθεση σειρών 287-288:

Answer

Πρόσθεση σειρών 299-300:

Answer

Πρόσθεση σειρών 311-312:

Answer

Πρόσθεση σειρών 323-324:

Answer

Πρόσθεση σειρών 335-336:

Answer

Πρόσθεση σειρών 347-348:

Answer

Πρόσθεση σειρών 359-360:

Answer

Αλλαγή σειρών 371-373 από:
σε:

Answer

Πρόσθεση σειρών 385-386:

Answer

Πρόσθεση σειρών 397-398:

Answer

Πρόσθεση σειρών 409-410:

Answer

Πρόσθεση σειρών 421-422:

Answer

Αλλαγή σειρών 431-434 από:

Answer

σε:

Answer

Αλλαγή σειρών 449-450 από:

Answer

σε:

Answer

Αλλαγή σειρών 467-468 από:

Answer

σε:

Answer

Αλλαγή σειρών 483-484 από:

Answer

σε:

Answer

Αλλαγή σειρών 498-499 από:

Answer

σε:

Answer

Αλλαγή σειρών 511-512 από:

Answer

σε:

Answer

Αλλαγή σειρών 523-524 από:

Answer

σε:

Answer

Αλλαγή σειρών 535-536 από:

Answer

σε:

Answer

Αλλαγή σειρών 551-552 από:

Answer

σε:

Answer

Αλλαγή σειρών 563-564 από:

Answer

σε:

Answer

Διαγραφή σειράς 568:
Αλλαγή σειρών 575-576 από:

Answer

σε:

Answer

Αλλαγή σειρών 587-588 από:

Answer

σε:

Answer

Αλλαγή σειρών 599-600 από:

Answer

σε:

Answer

22-07-2008 (16:00) από Άρης -
Αλλαγή σειρών 6-7 από:
σε:
Αλλαγή σειρών 16-17 από:
σε:
Αλλαγή σειρών 26-27 από:
σε:
Αλλαγή σειρών 36-37 από:
σε:
Αλλαγή σειρών 46-47 από:
σε:
Αλλαγή σειρών 56-57 από:
σε:
Αλλαγή σειρών 66-67 από:
σε:
Αλλαγή σειρών 76-78 από:
σε:
Αλλαγή σειρών 99-100 από:
σε:
Αλλαγή σειρών 109-110 από:
σε:
Αλλαγή σειρών 119-120 από:
σε:
Αλλαγή σειρών 129-130 από:
σε:
Αλλαγή σειρών 139-140 από:
σε:
Αλλαγή σειρών 149-150 από:
σε:
Αλλαγή σειρών 159-160 από:
σε:
Αλλαγή σειρών 169-170 από:
σε:
Αλλαγή σειρών 179-181 από:
σε:
Αλλαγή σειρών 201-202 από:
σε:
Αλλαγή σειρών 221-222 από:
σε:
Αλλαγή σειρών 231-232 από:
σε:
Αλλαγή σειρών 241-242 από:
σε:
Αλλαγή σειρών 251-252 από:
σε:
Αλλαγή σειρών 261-262 από:
σε:
Αλλαγή σειρών 271-272 από:
σε:
Αλλαγή σειρών 281-282 από:
σε:
Αλλαγή σειρών 291-292 από:
σε:
Αλλαγή σειρών 301-302 από:
σε:
Αλλαγή σειρών 311-313 από:
σε:
Αλλαγή σειρών 323-324 από:
σε:
Αλλαγή σειρών 333-334 από:
σε:
Αλλαγή σειρών 343-344 από:
σε:
Αλλαγή σειρών 353-354 από:
σε:
22-07-2008 (15:58) από Άρης -
Αλλαγή σειρών 6-7 από:

Answer: True

σε:

True

Αλλαγή σειρών 16-17 από:

Answer: To execute user programs and solve user problems.

σε:

To execute user programs and solve user problems.

Αλλαγή σειρών 26-27 από:

Answer: Their primary goal is convenience of the user; the secondary goal is efficient operation and allocation of all resources.

σε:

Their primary goal is convenience of the user; the secondary goal is efficient operation and allocation of all resources.

Αλλαγή σειρών 36-37 από:

Answer: The programmer himself operated the computer by using switches. He had to sign up for free time.

σε:

The programmer himself operated the computer by using switches. He had to sign up for free time.

Αλλαγή σειρών 46-47 από:

Answer: The user had to guess the amount of time needed to complete his job, fairly accurately, to avoid wasting machine time, and still allow enough time to complete the job.

σε:

The user had to guess the amount of time needed to complete his job, fairly accurately, to avoid wasting machine time, and still allow enough time to complete the job.

Αλλαγή σειρών 56-57 από:

Answer: Libraries of common functions, device drivers, assembly language, compilers.

σε:

Libraries of common functions, device drivers, assembly language, compilers.

Αλλαγή σειρών 66-67 από:

Answer: Creation of software libraries shared by all users, especially for input–output subroutines.

σε:

Creation of software libraries shared by all users, especially for input–output subroutines.

Αλλαγή σειρών 76-78 από:

Answer:

σε:
Πρόσθεση σειρών 93-94:
Αλλαγή σειρών 99-100 από:

Answer: A professional computer operator (or machine) groups jobs by characteristics and runs groups of similar jobs together, eff5ciently.

σε:

A professional computer operator (or machine) groups jobs by characteristics and runs groups of similar jobs together, eff5ciently.

Αλλαγή σειρών 109-110 από:

Answer: Less setup time, and thus less idle time of the computer.

σε:

Less setup time, and thus less idle time of the computer.

Αλλαγή σειρών 119-120 από:

Answer: System proceeds from one job to the next without human intervention.

σε:

System proceeds from one job to the next without human intervention.

Αλλαγή σειρών 129-130 από:

Answer: To avoid the delays inherent in having the operator changing jobs, and doing things manually.

σε:

To avoid the delays inherent in having the operator changing jobs, and doing things manually.

Αλλαγή σειρών 139-140 από:

Answer: To perform orderly and eff5cient automatic job sequencing, regardless of errors that might arise.

σε:

To perform orderly and eff5cient automatic job sequencing, regardless of errors that might arise.

Αλλαγή σειρών 149-150 από:

Answer: To let monitor know what resources are needed for current job, such as compiler, linker, data, etc., when to use them, and with which file; and to tell monitor when it reaches end of job.

σε:

To let monitor know what resources are needed for current job, such as compiler, linker, data, etc., when to use them, and with which file; and to tell monitor when it reaches end of job.

Αλλαγή σειρών 159-160 από:

Answer: Control card interpreter, device drivers, loader.

σε:

Control card interpreter, device drivers, loader.

Αλλαγή σειρών 169-170 από:

Answer: humans 0.5 to 5 characters/second paper tape 10 characters/second cards 1600 characters/second magnetic tape 160,000 characters/second.

σε:

humans 0.5 to 5 characters/second paper tape 10 characters/second cards 1600 characters/second magnetic tape 160,000 characters/second.

Αλλαγή σειρών 179-181 από:

Answer:

σε:
Πρόσθεση σειρών 185-186:
Αλλαγή σειράς 191 από:

Answer:

σε:

Answer

Πρόσθεση σειρών 195-196:
Αλλαγή σειρών 201-202 από:

Answer: The feature of systems that allows one input device to be replaced by another without changes in the users’ programs. Similarly with output. Thus, an old model card reader can be replaced with a new model; the old device driver programs are replaced by new ones; user programs need not be changed (though they may need to be relinked). Note: Many students respond that it is the ability to use different devices. This is false. You can write a FORTRAN II program to read cards and print to a line printer, two different devices; yet this does not imply device independence.

σε:

The feature of systems that allows one input device to be replaced by another without changes in the users’ programs. Similarly with output. Thus, an old model card reader can be replaced with a new model; the old device driver programs are replaced by new ones; user programs need not be changed (though they may need to be relinked). Note: Many students respond that it is the ability to use different devices. This is false. You can write a FORTRAN II program to read cards and print to a line printer, two different devices; yet this does not imply device independence.

Αλλαγή σειράς 211 από:

Answer:

σε:

Answer

Πρόσθεση σειρών 215-216:
Αλλαγή σειρών 221-222 από:

Answer: Off-line systems use magnetic tape. The system cannot read data from one end of the tape while the card reader writes data on the other end; it takes about 5 minutes to rewind the tape fully. With disks, it takes only milliseconds to alternate from the portion of the disk used for input and the portion for output.

σε:

Off-line systems use magnetic tape. The system cannot read data from one end of the tape while the card reader writes data on the other end; it takes about 5 minutes to rewind the tape fully. With disks, it takes only milliseconds to alternate from the portion of the disk used for input and the portion for output.

Αλλαγή σειρών 231-232 από:

Answer: An acronym for “Simultaneous Peripheral Operation On-Line.” It uses the disk as a large buffer for outputting data to line printers and other devices (like microfilm). It can also be used for input, but is generally used for output. Its main use is to prevent two users from alternately printing lines to the line printer on the same page, getting their output completely mixed together. It also helps in reducing idle time and overlapped I/O and CPU.

σε:

An acronym for “Simultaneous Peripheral Operation On-Line.” It uses the disk as a large buffer for outputting data to line printers and other devices (like microfilm). It can also be used for input, but is generally used for output. Its main use is to prevent two users from alternately printing lines to the line printer on the same page, getting their output completely mixed together. It also helps in reducing idle time and overlapped I/O and CPU.

Αλλαγή σειρών 241-242 από:

Answer: In I/O-bound programs, the CPU remains idle much of the time. In CPU-bound programs, the I/O processor remains idle. Note: I/O is never “faster” than CPU.

σε:

In I/O-bound programs, the CPU remains idle much of the time. In CPU-bound programs, the I/O processor remains idle. Note: I/O is never “faster” than CPU.

Αλλαγή σειρών 251-252 από:

Answer: In multiprogramming, several programs are in memory concurrently; the system switches among the programs for ef?cient processing, and minimal idle time. Note: Many students claim multiprogramming “always” keeps CPU and I/O devices busy; this is false; what is the computer to do at 3 AM Sunday morning, when there’s no job to run?

σε:

In multiprogramming, several programs are in memory concurrently; the system switches among the programs for ef?cient processing, and minimal idle time. Note: Many students claim multiprogramming “always” keeps CPU and I/O devices busy; this is false; what is the computer to do at 3 AM Sunday morning, when there’s no job to run?

Αλλαγή σειρών 261-262 από:

Answer: They are essentially devoid of interaction between user and program. All problems must be anticipated, and can’t be corrected on-line.

σε:

They are essentially devoid of interaction between user and program. All problems must be anticipated, and can’t be corrected on-line.

Αλλαγή σειρών 271-272 από:

Answer: Users can’t interact with their jobs to fix problems. They must anticipate problems or else debugging could be a mess with machine-language dumps. There may also be long turnaround times.

σε:

Users can’t interact with their jobs to fix problems. They must anticipate problems or else debugging could be a mess with machine-language dumps. There may also be long turnaround times.

Αλλαγή σειρών 281-282 από:

Answer: Using scheduling and multiprogramming to provide an economical interactive system of two or more users.

σε:

Using scheduling and multiprogramming to provide an economical interactive system of two or more users.

Αλλαγή σειρών 291-292 από:

Answer: Interaction with computer while program is running, short response times (usually less than 10 seconds).

σε:

Interaction with computer while program is running, short response times (usually less than 10 seconds).

Αλλαγή σειρών 301-302 από:

Answer: Each user is given a brief time-slice for her job, in round-robin fashion. Her job continues until the time-slice ends. Then her job stops, until it is her turn again.

σε:

Each user is given a brief time-slice for her job, in round-robin fashion. Her job continues until the time-slice ends. Then her job stops, until it is her turn again.

Αλλαγή σειρών 311-313 από:

Answer:

σε:
Πρόσθεση σειρών 317-318:
Αλλαγή σειρών 323-324 από:

Answer: A system with two or more CPUs.

σε:

A system with two or more CPUs.

Αλλαγή σειρών 333-334 από:

Answer: A master computer controls the actions of various slave computers.

σε:

A master computer controls the actions of various slave computers.

Αλλαγή σειρών 343-344 από:

Answer: A system used to control a dedicated application.

σε:

A system used to control a dedicated application.

Αλλαγή σειρών 353-354 από:

Answer: In time-sharing, fast response is desirable, but not required. In real-time systems, processing must be completed within certain time constraints appropriate for the system.

σε:

In time-sharing, fast response is desirable, but not required. In real-time systems, processing must be completed within certain time constraints appropriate for the system.

Αλλαγή σειράς 363 από:

Answer:

σε:

Answer

Πρόσθεση σειρών 370-371:
Πρόσθεση σειράς 388:
Πρόσθεση σειράς 415:
Πρόσθεση σειράς 496:
22-07-2008 (15:17) από Άρης -
Πρόσθεση σειράς 13:
Αλλαγή σειρών 21-24 από:

Describe how the earliest computers were used.

Answer: The programmer himself operated the computer by using switches. He had to sign up for free time.

σε:

Describe how the earliest computers were used.

Answer: The programmer himself operated the computer by using switches. He had to sign up for free time.

Αλλαγή σειρών 27-30 από:

What problems were involved in these earliest computers?

Answer: The user had to guess the amount of time needed to complete his job, fairly accurately, to avoid wasting machine time, and still allow enough time to complete the job.

σε:

What problems were involved in these earliest computers?

Answer: The user had to guess the amount of time needed to complete his job, fairly accurately, to avoid wasting machine time, and still allow enough time to complete the job.

Αλλαγή σειρών 34-37 από:

What software was added to increase user efficiency?

Answer: Libraries of common functions, device drivers, assembly language, compilers.

σε:

What software was added to increase user efficiency?

Answer: Libraries of common functions, device drivers, assembly language, compilers.

Αλλαγή σειρών 40-43 από:

What effect did adding I/O devices have on software?

Answer: Creation of software libraries shared by all users, especially for input–output subroutines.

σε:

What effect did adding I/O devices have on software?

Answer: Creation of software libraries shared by all users, especially for input–output subroutines.

Αλλαγή σειρών 46-48 από:

What factors contributed to the setup time for a job? List them.

Answer:

σε:

What factors contributed to the setup time for a job? List them.

Answer:

Αλλαγή σειρών 65-68 από:

What is a simple batch system?

Answer: A professional computer operator (or machine) groups jobs by characteristics and runs groups of similar jobs together, eff5ciently.

σε:

What is a simple batch system?

Answer: A professional computer operator (or machine) groups jobs by characteristics and runs groups of similar jobs together, eff5ciently.

Αλλαγή σειρών 71-74 από:

Why use simple batch systems, in preference to early systems?

Answer: Less setup time, and thus less idle time of the computer.

σε:

Why use simple batch systems, in preference to early systems?

Answer: Less setup time, and thus less idle time of the computer.

Αλλαγή σειρών 77-80 από:

What is “automatic job sequencing”?

Answer: System proceeds from one job to the next without human intervention.

σε:

What is “automatic job sequencing”?

Answer: System proceeds from one job to the next without human intervention.

Αλλαγή σειρών 83-86 από:

Why have automatic job sequencing?

Answer: To avoid the delays inherent in having the operator changing jobs, and doing things manually.

σε:

Why have automatic job sequencing?

Answer: To avoid the delays inherent in having the operator changing jobs, and doing things manually.

Αλλαγή σειρών 89-92 από:

What is the purpose of the “resident monitor”?

Answer: To perform orderly and eff5cient automatic job sequencing, regardless of errors that might arise.

σε:

What is the purpose of the “resident monitor”?

Answer: To perform orderly and eff5cient automatic job sequencing, regardless of errors that might arise.

Αλλαγή σειρών 95-98 από:

What were control cards used for?

Answer: To let monitor know what resources are needed for current job, such as compiler, linker, data, etc., when to use them, and with which f5le; and to tell monitor when it reaches end of job.

σε:

What were control cards used for?

Answer: To let monitor know what resources are needed for current job, such as compiler, linker, data, etc., when to use them, and with which file; and to tell monitor when it reaches end of job.

Αλλαγή σειρών 101-104 από:

List parts of the monitor.

Answer: Control card interpreter, device drivers, loader.

σε:

List parts of the monitor.

Answer: Control card interpreter, device drivers, loader.

Αλλαγή σειρών 107-110 από:

Compare speeds of various I/O devices, in characters/second.

Answer: humans 0.5 to 5 characters/second paper tape 10 characters/second cards 1600 characters/second magnetic tape 160,000 characters/second.

σε:

Compare speeds of various I/O devices, in characters/second.

Answer: humans 0.5 to 5 characters/second paper tape 10 characters/second cards 1600 characters/second magnetic tape 160,000 characters/second.

Αλλαγή σειρών 113-116 από:

Describe two kinds of off-line operations.

Answer:

σε:

Describe two kinds of off-line operations.

Answer:

Αλλαγή σειρών 121-123 από:

Describe two approaches to off-line processing.

Answer:

σε:

Describe two approaches to off-line processing.

Answer:

Αλλαγή σειρών 129-132 από:

What is device independence?

Answer: The feature of systems that allows one input device to be replaced by another without changes in the users’ programs. Similarly with output. Thus, an old model card reader can be replaced with a new model; the old device driver programs are replaced by new ones; user programs need not be changed (though they may need to be relinked). Note: Many students respond that it is the ability to use different devices. This is false. You can write a FORTRAN II program to read cards and print to a line printer, two different devices; yet this does not imply device independence.

σε:

What is device independence?

Answer: The feature of systems that allows one input device to be replaced by another without changes in the users’ programs. Similarly with output. Thus, an old model card reader can be replaced with a new model; the old device driver programs are replaced by new ones; user programs need not be changed (though they may need to be relinked). Note: Many students respond that it is the ability to use different devices. This is false. You can write a FORTRAN II program to read cards and print to a line printer, two different devices; yet this does not imply device independence.

Αλλαγή σειρών 135-137 από:

What were the advantages of off-line operations?

Answer:

σε:

What were the advantages of off-line operations?

Answer:

Αλλαγή σειρών 143-146 από:

How have disk systems helped solved problems inherent in off-line systems?

Answer: Off-line systems use magnetic tape. The system cannot read data from one end of the tape while the card reader writes data on the other end; it takes about 5 minutes to rewind the tape fully. With disks, it takes only milliseconds to alternate from the portion of the disk used for input and the portion for output.

σε:

How have disk systems helped solved problems inherent in off-line systems?

Answer: Off-line systems use magnetic tape. The system cannot read data from one end of the tape while the card reader writes data on the other end; it takes about 5 minutes to rewind the tape fully. With disks, it takes only milliseconds to alternate from the portion of the disk used for input and the portion for output.

Αλλαγή σειρών 149-152 από:

What is spooling?

Answer: An acronym for “Simultaneous Peripheral Operation On-Line.” It uses the disk as a large buffer for outputting data to line printers and other devices (like microfilm). It can also be used for input, but is generally used for output. Its main use is to prevent two users from alternately printing lines to the line printer on the same page, getting their output completely mixed together. It also helps in reducing idle time and overlapped I/O and CPU.

σε:

What is spooling?

Answer: An acronym for “Simultaneous Peripheral Operation On-Line.” It uses the disk as a large buffer for outputting data to line printers and other devices (like microfilm). It can also be used for input, but is generally used for output. Its main use is to prevent two users from alternately printing lines to the line printer on the same page, getting their output completely mixed together. It also helps in reducing idle time and overlapped I/O and CPU.

Αλλαγή σειρών 155-158 από:

How do I/O-bound and CPU-bound programs differ?

Answer: In I/O-bound programs, the CPU remains idle much of the time. In CPU-bound programs, the I/O processor remains idle. Note: I/O is never “faster” than CPU.

σε:

How do I/O-bound and CPU-bound programs differ?

Answer: In I/O-bound programs, the CPU remains idle much of the time. In CPU-bound programs, the I/O processor remains idle. Note: I/O is never “faster” than CPU.

Αλλαγή σειρών 161-164 από:

What is multiprogramming?

Answer: In multiprogramming, several programs are in memory concurrently; the system switches among the programs for ef?cient processing, and minimal idle time. Note: Many students claim multiprogramming “always” keeps CPU and I/O devices busy; this is false; what is the computer to do at 3 AM Sunday morning, when there’s no job to run?

σε:

What is multiprogramming?

Answer: In multiprogramming, several programs are in memory concurrently; the system switches among the programs for ef?cient processing, and minimal idle time. Note: Many students claim multiprogramming “always” keeps CPU and I/O devices busy; this is false; what is the computer to do at 3 AM Sunday morning, when there’s no job to run?

Αλλαγή σειρών 167-170 από:

Define batch systems in terms of interaction.

Answer: They are essentially devoid of interaction between user and program. All problems must be anticipated, and can’t be corrected on-line.

σε:

Define batch systems in terms of interaction.

Answer: They are essentially devoid of interaction between user and program. All problems must be anticipated, and can’t be corrected on-line.

Αλλαγή σειρών 173-176 από:

In what ways are batch systems inconvenient for users?

Answer: Users can’t interact with their jobs to fix problems. They must anticipate problems or else debugging could be a mess with machine-language dumps. There may also be long turnaround times.

σε:

In what ways are batch systems inconvenient for users?

Answer: Users can’t interact with their jobs to fix problems. They must anticipate problems or else debugging could be a mess with machine-language dumps. There may also be long turnaround times.

Αλλαγή σειρών 179-182 από:

What is time-sharing?

Answer: Using scheduling and multiprogramming to provide an economical interactive system of two or more users.

σε:

What is time-sharing?

Answer: Using scheduling and multiprogramming to provide an economical interactive system of two or more users.

Αλλαγή σειρών 185-188 από:

What are the main advantages of a time-share system?

Answer: Interaction with computer while program is running, short response times (usually less than 10 seconds).

σε:

What are the main advantages of a time-share system?

Answer: Interaction with computer while program is running, short response times (usually less than 10 seconds).

Αλλαγή σειρών 191-194 από:

How is time-sharing usually implemented?

Answer: Each user is given a brief time-slice for her job, in round-robin fashion. Her job continues until the time-slice ends. Then her job stops, until it is her turn again.

σε:

How is time-sharing usually implemented?

Answer: Each user is given a brief time-slice for her job, in round-robin fashion. Her job continues until the time-slice ends. Then her job stops, until it is her turn again.

Αλλαγή σειρών 197-199 από:

How do MULTICS and UNIX differ?

Answer:

σε:

How do MULTICS and UNIX differ?

Answer:

Αλλαγή σειρών 205-208 από:

What is a multiprocessor system?

Answer: A system with two or more CPUs.

σε:

What is a multiprocessor system?

Answer: A system with two or more CPUs.

Αλλαγή σειρών 211-214 από:

What is a master/slave processor system?

Answer: A master computer controls the actions of various slave computers.

σε:

What is a master/slave processor system?

Answer: A master computer controls the actions of various slave computers.

Αλλαγή σειρών 217-220 από:

What does RJE stand for?

Answer: Remote Job Entry.

σε:

What is a real-time system?

Answer: A system used to control a dedicated application.

Αλλαγή σειρών 222-225 από:

What is a real-time system?

Answer: A system used to control a dedicated application.

σε:

How does a real-time system differ from time-share?

Answer: In time-sharing, fast response is desirable, but not required. In real-time systems, processing must be completed within certain time constraints appropriate for the system.

Αλλαγή σειρών 229-237 από:

How does a real-time system differ from time-share?

Answer: In time-sharing, fast response is desirable, but not required. In real-time systems, processing must be completed within certain time constraints appropriate for the system.


List several examples of real-time systems.

Answer:

σε:

List several examples of real-time systems.

Answer:

Αλλαγή σειρών 240-241 από:

What are the three main purposes of an operating system?

σε:

What are the three main purposes of an operating system?

Αλλαγή σειρών 246-249 από:

There are several possible purposes of an operating system: To provide an environment for a computer user to execute programs on computer hardware in a convenient and efficient manner. To allocate the separate resources of the computer as needed to solve the problem given. The allocation process should be as fair and efficient as possible. As a control program it serves two major functions:

  1. supervision of the execution of user programs to prevent errors and improper use of the computer, and
  2. management of the operation and control of I/O devices.
σε:

There are several possible purposes of an operating system:

  1. To provide an environment for a computer user to execute programs on computer hardware in a convenient and efficient manner.
  2. To allocate the separate resources of the computer as needed to solve the problem given.
  3. The allocation process should be as fair and efficient as possible. As a control program it serves two major functions:
* supervision of the execution of user programs to prevent errors and improper use of the computer, and
* management of the operation and control of I/O devices.
22-07-2008 (14:55) από Άρης -
Αλλαγή σειρών 4-6 από:

True/False: An operating system can be viewed as “resource allocator” to control various I/O devices and user programs.

Answer: True

σε:

True/False: An operating system can be viewed as “resource allocator” to control various I/O devices and user programs.

Answer: True

Αλλαγή σειρών 9-11 από:

What is the fundamental goal of computer systems?

Answer: To execute user programs and solve user problems.

σε:

What is the fundamental goal of computer systems?

Answer: To execute user programs and solve user problems.

Αλλαγή σειρών 14-17 από:

Define operating systems in terms of what they do.

Answer: Their primary goal is convenience of the user; the secondary goal is efficient operation and allocation of all resources.

σε:

Define operating systems in terms of what they do.

Answer: Their primary goal is convenience of the user; the secondary goal is efficient operation and allocation of all resources.

22-07-2008 (14:23) από Άρης -
Αλλαγή σειράς 1 από:
σε:
Αλλαγή σειρών 22-23 από:

What problems were involved in these earliest computers? Answer: The user had to guess the amount of time needed to complete his job, fairly accurately, to avoid wasting machine time, and still allow enough time to complete the job. 1.6 What software was added to increase user ef?ciency? Answer: Libraries of common functions, device drivers, assembly language, compilers. 1.7 What effect did adding I/O devices have on software? Answer: Creation of software libraries shared by all users, especially for input–output subroutines. 1.8 What factors contributed to the setup time for a job? List them. Answer: a. Load loader tape. b. Load compiler tape. c. Load source program. d. Execute compiler with output going to tape. e. Rewind each tape. f. If output of compiler was assembly language, load assembler. g. Rewind tapes. h. Execute assembler with object output to tape. i. Rewind tapes. j. Load the object program from tape. k. Execute the program with output going to paper tape. l. Run paper tape output through teletype to get printed copy. Note: On some systems, the loader had to be reloaded after many of the above steps. 1.9 What is a simple batch system? Answer: A professional computer operator (or machine) groups jobs by characteristics and runs groups of similar jobs together, ef?ciently. 1.10 Why use simple batch systems, in preference to early systems? Answer: Less setup time, and thus less idle time of the computer. 1.11 What is “automatic job sequencing”? Answer: System proceeds from one job to the next without human intervention. 1.12 Why have automatic job sequencing? Answer: To avoid the delays inherent in having the operator changing jobs, and doing things manually. 1.13 What is the purpose of the “resident monitor”? Answer: To perform orderly and ef?cient automatic job sequencing, regardless of errors that might arise. 1.14 What were control cards used for? Answer: To let monitor know what resources are needed for current job, such as compiler, linker, data, etc., when to use them, and with which ?le; and to tell monitor when it reaches end of job. 1.15 List parts of the monitor. Answer: Control card interpreter, device drivers, loader. 1.16 Compare speeds of various I/O devices, in characters/second. Answer: humans 0.5 to 5 characters/second paper tape 10 characters/second cards 1600 characters/second magnetic tape 160,000 characters/second 1.17 Describe two kinds of off-line operations. Answer: a. Cards copied to magnetic tape, which was then mounted on computer; output of computer was dumped to magnetic tape, which was then mounted for output to a printer. b. Satellite computers read cards onto magnetic tape, which could transfer information to the main computer without remounting. 1.18 Describe two approaches to off-line processing. Answer: a. Data is read from cards onto magnetic tapes, which are in turn mounted manually on the main system. Printer output from the main system is saved on magnetic tape, which is then mounted manually on a tape reader attached to a line printer. b. Data is read from cards onto magnetic tapes. But the tapes are not removed from their drives. Instead, a small computer reads them and sends the information to the main system. Similarly with output. Note: Main difference here is that data was manually exchanged between main computer and off-line system. 1.19 What is device independence? Answer: The feature of systems that allows one input device to be replaced by another without changes in the users’ programs. Similarly with output. Thus, an old model card reader can be replaced with a new model; the old device driver programs are replaced by new ones; user programs need not be changed (though they may need to be relinked). Note: Many students respond that it is the ability to use different devices. This is false. You can write a FORTRAN II program to read cards and print to a line printer, two different devices; yet this does not imply device independence. 1.20 What were the advantages of off-line operations? Answer: a. Main computer no longer constrained by speed of card reader. b. Application programs used logical I/O devices instead of physical I/O devices; programs didn’t have to be rewritten when new I/O devices replaced old ones. 1.21 How have disk systems helped solved problems inherent in off-line systems? Answer: Off-line systems use magnetic tape. The system cannot read data from one end of the tape while the card reader writes data on the other end; it takes about 5 minutes to rewind the tape fully. With disks, it takes only milliseconds to alternate from the portion of the disk used for input and the portion for output. 1.22 What is spooling? Answer: An acronym for “Simultaneous Peripheral Operation On-Line.” It uses the disk as a large buffer for outputting data to line printers and other devices (like micro?lm). It can also be used for input, but is generally used for output. Its main use is to prevent two users from alternately printing lines to the line printer on the same page, getting their output completely mixed together. It also helps in reducing idle time and overlapped I/O and CPU. 1.23 How do I/O-bound and CPU-bound programs differ? Answer: In I/O-bound programs, the CPU remains idle much of the time. In CPU-bound programs, the I/O processor remains idle. Note: I/O is never “faster” than CPU. 1.24 What is multiprogramming? Answer: In multiprogramming, several programs are in memory concurrently; the system switches among the programs for ef?cient processing, and minimal idle time. Note: Many students claim multiprogramming “always” keeps CPU and I/O devices busy; this is false; what is the computer to do at 3 AM Sunday morning, when there’s no job to run? 1.25 De?ne batch systems in terms of interaction. Answer: They are essentially devoid of interaction between user and program. All problems must be anticipated, and can’t be corrected on-line. 1.26 In what ways are batch systems inconvenient for users? Answer: Users can’t interact with their jobs to ?x problems. They must anticipate problems or else debugging could be a mess with machine-language dumps. There may also be long turnaround times. 1.27 What is time-sharing? Answer: Using scheduling and multiprogramming to provide an economical interactive system of two or more users. 1.28 What are the main advantages of a time-share system? Answer: Interaction with computer while program is running, short response times (usually less than 10 seconds). 1.29 How is time-sharing usually implemented? Answer: Each user is given a brief time-slice for her job, in round-robin fashion. Her job continues until the time-slice ends. Then her job stops, until it is her turn again. 1.30 How do MULTICS and UNIX differ? Answer: * MULTICS was a time-sharing system created on a large mainframe GE computer (since then taken over by Honeywell), by GE, by Bell Labs, and by faculty at MIT. It was very ?exible, and oriented toward programmers. * UNIX was inspired by MULTICS; but it was designed by Ritchie and Thompson in 1974 at Bell Labs for use on minicomputers, like the PDP-11. It was designed for program development, using a device-independent ?le system. 1.31 What is a multiprocessor system? Answer: A system with two or more CPUs. 1.32 What is a master/slave processor system? Answer: A master computer controls the actions of various slave computers. 1.33 What does RJE stand for? Answer: Remote Job Entry. 1.34 What is a real-time system? Answer: A system used to control a dedicated application. 1.35 How does a real-time system differ from time-share? Answer: In time-sharing, fast response is desirable, but not required. In real-time systems, processing must be completed within certain time constraints appropriate for the system. 1.36 List several examples of real-time systems. Answer: a. Control of a nuclear reactor, to prevent chain reaction. b. Control of a space ship, to avoid collision with meteors. c. Control of manufacturing equipment, such as lathes, canners, etc. d. Detecting patients’ conditions in Intensive Care Units in hospitals. e. Collecting data on cosmic rays in physics research.

σε:

What problems were involved in these earliest computers?

Answer: The user had to guess the amount of time needed to complete his job, fairly accurately, to avoid wasting machine time, and still allow enough time to complete the job.

Αλλαγή σειρών 28-38 από:

What are the three main purposes of an operating system?

Answer

There are several possible purposes of an operating system: To provide an environment for a computer user to execute programs on computer hardware in a convenient and efficient manner. To allocate the separate resources of the computer as needed to solve the problem given. The allocation process should be as fair and efficient as possible. As a control program it serves two major functions:

  1. supervision of the execution of user programs to prevent errors and improper use of the computer, and
  2. management of the operation and control of I/O devices.
σε:

What software was added to increase user efficiency?

Answer: Libraries of common functions, device drivers, assembly language, compilers.

Αλλαγή σειρών 34-46 από:

List the four steps that are necessary to run a program on a completely dedicated machine.

Answer

  1. Reserve machine time.
  2. Manually load program into memory
  3. Load starting address and begin execution
  4. Monitor and control execution of program from console.
σε:

What effect did adding I/O devices have on software?

Answer: Creation of software libraries shared by all users, especially for input–output subroutines.

Αλλαγή σειρών 40-48 από:

An extreme method of spooling, known as staging a tape, is to read the entire contents of a magnetic tape onto disk before using it. Discuss the main advantage of such a scheme.

Answer

No I/O is needed while the data is being processed, so staging is more simple than spooling. All of the data are on-line before they are needed so a process can run at full speed. The disadvantage is that more time is spent, before the process starts, in loading the data, and more disk space is consumed in storing the entire tape contents.

σε:

What factors contributed to the setup time for a job? List them.

Answer:

  1. Load loader tape.
  2. Load compiler tape.
  3. Load source program.
  4. Execute compiler with output going to tape.
  5. Rewind each tape
  6. If output of compiler was assembly language, load assembler.
  7. Rewind tapes.
  8. Execute assembler with object output to tape.
  9. Rewind tapes.
  10. Load the object program from tape.
  11. Execute the program with output going to paper tape.
  12. Run paper tape output through teletype to get printed copy.

Note: On some systems, the loader had to be reloaded after many of the above steps.

Αλλαγή σειρών 59-72 από:

In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems.

  1. What are two such problems?
  2. Can we ensure the same degree of security in a time-shared machine as we have in a dedicated machine?

Explain your answer.

Answer

  1. Stealing or copying one’s programs or data; using system resources (CPU, memory, disk space, peripherals) without proper accounting.
  2. Probably not, since any protection scheme devised by man can inevitably be broken by him, and the more complex the scheme, the more difficult it is to feel confident of its correct implementation.
σε:

What is a simple batch system?

Answer: A professional computer operator (or machine) groups jobs by characteristics and runs groups of similar jobs together, eff5ciently.

Αλλαγή σειρών 65-74 από:

What is the main advantage of multiprogramming?

Answer

Multiprogramming makes efficient use of the CPU by overlapping the demands for the CPU and its I/O devices from various users. It attempts to increase CPU utilization by always having something for the CPU to execute.

σε:

Why use simple batch systems, in preference to early systems?

Answer: Less setup time, and thus less idle time of the computer.

Αλλαγή σειρών 71-80 από:

What are the main differences between operating systems for mainframe computers and personal computers?

Answer

Personal computer operating systems are not concerned with fair use, or maximal use, of computer facilities. Instead, they try to optimize the usefulness of the computer for an individual user, usually at the expense of efficiency. Consider how many CPU cycles are used by graphical user interfaces (GUIs). Mainframe operating systems need more complex scheduling and I/O algorithms to keep the various system components busy.

σε:

What is “automatic job sequencing”?

Answer: System proceeds from one job to the next without human intervention.

Αλλαγή σειρών 77-90 από:

Define the essential properties of the following types of operating systems: Batch Interactive Time sharing Real time Distributed.

Answer

  1. Batch. Jobs with similar needs are batched together and run through the computer as a group by an operator or automatic job sequencer. Performance is increased by attempting to keep CPU and I/O devices busy at all times through buffering, off-line operation, spooling, and multiprogramming. Batch is good for executing large jobs that need little interaction; it can be submitted and picked up later. Answers to Exercises.
  2. Interactive. Composed of many short transactions where the results of the next transaction may be unpredictable. Response time needs to be short (seconds) since the user submits and waits for the result.
  3. Time sharing.Uses CPU scheduling and multiprogramming to provide economical interactive use of a system. The CPU switches rapidly from one user to another. Instead of having a job defined by spooled card images, each program reads its next control card from the terminal, and output is normally printed immediately to the screen.
  4. Real time. Often used in a dedicated application. The system reads information from sensors and must respond within a fixed amount of time to ensure correct performance.
  5. Distributed. Distributes computation among several physical processors. The processors do not share memory or a clock. Instead, each processor has its own local memory. They communicate with each other through various communication lines, such as a high-speed bus or telephone line.
σε:

Why have automatic job sequencing?

Answer: To avoid the delays inherent in having the operator changing jobs, and doing things manually.

Αλλαγή σειρών 83-92 από:

We have stressed the need for an operating system to make efficient use of the computing hardware. When is it appropriate for the operating system to forsake this principle and to “waste” resources? Why is such a system not really wasteful?

Answer

Single-user systems should maximize use of the system for the user. A GUI might “waste” CPU cycles but it optimizes the user’s interaction with the system.

σε:

What is the purpose of the “resident monitor”?

Answer: To perform orderly and eff5cient automatic job sequencing, regardless of errors that might arise.

Αλλαγή σειρών 89-98 από:

Under what circumstances would a user be better off using a time-sharing system, rather than a personal computer or single-user workstation?

Answer

When there are few other users, the task is large, and the hardware is fast, timesharing makes sense. The full power of the system can be brought to bear on the user’s problem. The problem can be solved faster than on a personal computer. Another case is when there are lots of other users needing resources at the same time. A personal computer is best when the job is small enough to be executed reasonably on it, and when performance is sufficient to execute the program to the user’s satisfaction.

σε:

What were control cards used for?

Answer: To let monitor know what resources are needed for current job, such as compiler, linker, data, etc., when to use them, and with which f5le; and to tell monitor when it reaches end of job.


List parts of the monitor.

Answer: Control card interpreter, device drivers, loader.

Αλλαγή σειρών 101-110 από:

Describe the differences between symmetric and asymmetric multiprocessing. What are three advantages and one disadvantage of multiprocessor systems?

Answer

Symmetric multiprocessing treats all processors as equals, and I/O can be processed on any CPU. Asymmetric multiprocessing has one master CPU and the remainder CPUs are slaves. The master distributes tasks among the slaves, and I/O is usually done by the master only. Multiprocessors can save money, by not duplicating power supplies, housings, and peripherals. They can execute programs more quickly, and can have increased reliability. They are also more complex in both hardware and software than uniprocessor systems.

σε:

Compare speeds of various I/O devices, in characters/second.

Answer: humans 0.5 to 5 characters/second paper tape 10 characters/second cards 1600 characters/second magnetic tape 160,000 characters/second.

Αλλαγή σειρών 107-116 από:

Why are distributed systems desirable?

Answer

Distributed systems can provide resource sharing, computation speedup, increased reliability, and the ability to communicate with remote sites.

σε:

Describe two kinds of off-line operations.

Answer:

  1. Cards copied to magnetic tape, which was then mounted on computer; output of computer was dumped to magnetic tape, which was then mounted for output to a printer
  2. Satellite computers read cards onto magnetic tape, which could transfer information to the main computer without remounting.
Αλλαγή σειρών 116-125 από:

What is the main difficulty that a programmer must overcome in writing an operating system for a real-time environment?

Answer

The main difficulty is keeping the operating system within the fixed time constraints of a real-time system. If the system does not complete a task in a certain time, it could cause a breakdown of the entire system it is running. Therefore when writing an operating system for a real-time system, the writer must be sure that his scheduling schemes don’t allow response time to exceed the time constraint.

σε:

Describe two approaches to off-line processing.

Answer:

  1. Data is read from cards onto magnetic tapes, which are in turn mounted manually on the main system. Printer output from the main system is saved on magnetic tape, which is then mounted manually on a tape reader attached to a line printer.
  2. Data is read from cards onto magnetic tapes. But the tapes are not removed from their drives. Instead, a small computer reads them and sends the information to the main system. Similarly with output. Note: Main difference here is that data was manually exchanged between main computer and off-line system.
Πρόσθεση σειρών 124-394:

What is device independence?

Answer: The feature of systems that allows one input device to be replaced by another without changes in the users’ programs. Similarly with output. Thus, an old model card reader can be replaced with a new model; the old device driver programs are replaced by new ones; user programs need not be changed (though they may need to be relinked). Note: Many students respond that it is the ability to use different devices. This is false. You can write a FORTRAN II program to read cards and print to a line printer, two different devices; yet this does not imply device independence.


What were the advantages of off-line operations?

Answer:

  1. Main computer no longer constrained by speed of card reader.
  2. Application programs used logical I/O devices instead of physical I/O devices; programs didn’t have to be rewritten when new I/O devices replaced old ones.

How have disk systems helped solved problems inherent in off-line systems?

Answer: Off-line systems use magnetic tape. The system cannot read data from one end of the tape while the card reader writes data on the other end; it takes about 5 minutes to rewind the tape fully. With disks, it takes only milliseconds to alternate from the portion of the disk used for input and the portion for output.


What is spooling?

Answer: An acronym for “Simultaneous Peripheral Operation On-Line.” It uses the disk as a large buffer for outputting data to line printers and other devices (like microfilm). It can also be used for input, but is generally used for output. Its main use is to prevent two users from alternately printing lines to the line printer on the same page, getting their output completely mixed together. It also helps in reducing idle time and overlapped I/O and CPU.


How do I/O-bound and CPU-bound programs differ?

Answer: In I/O-bound programs, the CPU remains idle much of the time. In CPU-bound programs, the I/O processor remains idle. Note: I/O is never “faster” than CPU.


What is multiprogramming?

Answer: In multiprogramming, several programs are in memory concurrently; the system switches among the programs for ef?cient processing, and minimal idle time. Note: Many students claim multiprogramming “always” keeps CPU and I/O devices busy; this is false; what is the computer to do at 3 AM Sunday morning, when there’s no job to run?


Define batch systems in terms of interaction.

Answer: They are essentially devoid of interaction between user and program. All problems must be anticipated, and can’t be corrected on-line.


In what ways are batch systems inconvenient for users?

Answer: Users can’t interact with their jobs to fix problems. They must anticipate problems or else debugging could be a mess with machine-language dumps. There may also be long turnaround times.


What is time-sharing?

Answer: Using scheduling and multiprogramming to provide an economical interactive system of two or more users.


What are the main advantages of a time-share system?

Answer: Interaction with computer while program is running, short response times (usually less than 10 seconds).


How is time-sharing usually implemented?

Answer: Each user is given a brief time-slice for her job, in round-robin fashion. Her job continues until the time-slice ends. Then her job stops, until it is her turn again.


How do MULTICS and UNIX differ?

Answer:

  • MULTICS was a time-sharing system created on a large mainframe GE computer (since then taken over by Honeywell), by GE, by Bell Labs, and by faculty at MIT. It was very ?exible, and oriented toward programmers.
  • UNIX was inspired by MULTICS; but it was designed by Ritchie and Thompson in 1974 at Bell Labs for use on minicomputers, like the PDP-11. It was designed for program development, using a device-independent file system.

What is a multiprocessor system?

Answer: A system with two or more CPUs.


What is a master/slave processor system?

Answer: A master computer controls the actions of various slave computers.


What does RJE stand for?

Answer: Remote Job Entry.


What is a real-time system?

Answer: A system used to control a dedicated application.


How does a real-time system differ from time-share?

Answer: In time-sharing, fast response is desirable, but not required. In real-time systems, processing must be completed within certain time constraints appropriate for the system.


List several examples of real-time systems.

Answer:

  • Control of a nuclear reactor, to prevent chain reaction.
  • Control of a space ship, to avoid collision with meteors.
  • Control of manufacturing equipment, such as lathes, canners, etc.
  • Detecting patients’ conditions in Intensive Care Units in hospitals.
  • Collecting data on cosmic rays in physics research.

What are the three main purposes of an operating system?

Answer

There are several possible purposes of an operating system: To provide an environment for a computer user to execute programs on computer hardware in a convenient and efficient manner. To allocate the separate resources of the computer as needed to solve the problem given. The allocation process should be as fair and efficient as possible. As a control program it serves two major functions:

  1. supervision of the execution of user programs to prevent errors and improper use of the computer, and
  2. management of the operation and control of I/O devices.

List the four steps that are necessary to run a program on a completely dedicated machine.

Answer

  1. Reserve machine time.
  2. Manually load program into memory
  3. Load starting address and begin execution
  4. Monitor and control execution of program from console.

An extreme method of spooling, known as staging a tape, is to read the entire contents of a magnetic tape onto disk before using it. Discuss the main advantage of such a scheme.

Answer

No I/O is needed while the data is being processed, so staging is more simple than spooling. All of the data are on-line before they are needed so a process can run at full speed. The disadvantage is that more time is spent, before the process starts, in loading the data, and more disk space is consumed in storing the entire tape contents.


In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems.

  1. What are two such problems?
  2. Can we ensure the same degree of security in a time-shared machine as we have in a dedicated machine?

Explain your answer.

Answer

  1. Stealing or copying one’s programs or data; using system resources (CPU, memory, disk space, peripherals) without proper accounting.
  2. Probably not, since any protection scheme devised by man can inevitably be broken by him, and the more complex the scheme, the more difficult it is to feel confident of its correct implementation.

What is the main advantage of multiprogramming?

Answer

Multiprogramming makes efficient use of the CPU by overlapping the demands for the CPU and its I/O devices from various users. It attempts to increase CPU utilization by always having something for the CPU to execute.


What are the main differences between operating systems for mainframe computers and personal computers?

Answer

Personal computer operating systems are not concerned with fair use, or maximal use, of computer facilities. Instead, they try to optimize the usefulness of the computer for an individual user, usually at the expense of efficiency. Consider how many CPU cycles are used by graphical user interfaces (GUIs). Mainframe operating systems need more complex scheduling and I/O algorithms to keep the various system components busy.


Define the essential properties of the following types of operating systems: Batch Interactive Time sharing Real time Distributed.

Answer

  1. Batch. Jobs with similar needs are batched together and run through the computer as a group by an operator or automatic job sequencer. Performance is increased by attempting to keep CPU and I/O devices busy at all times through buffering, off-line operation, spooling, and multiprogramming. Batch is good for executing large jobs that need little interaction; it can be submitted and picked up later. Answers to Exercises.
  2. Interactive. Composed of many short transactions where the results of the next transaction may be unpredictable. Response time needs to be short (seconds) since the user submits and waits for the result.
  3. Time sharing.Uses CPU scheduling and multiprogramming to provide economical interactive use of a system. The CPU switches rapidly from one user to another. Instead of having a job defined by spooled card images, each program reads its next control card from the terminal, and output is normally printed immediately to the screen.
  4. Real time. Often used in a dedicated application. The system reads information from sensors and must respond within a fixed amount of time to ensure correct performance.
  5. Distributed. Distributes computation among several physical processors. The processors do not share memory or a clock. Instead, each processor has its own local memory. They communicate with each other through various communication lines, such as a high-speed bus or telephone line.

We have stressed the need for an operating system to make efficient use of the computing hardware. When is it appropriate for the operating system to forsake this principle and to “waste” resources? Why is such a system not really wasteful?

Answer

Single-user systems should maximize use of the system for the user. A GUI might “waste” CPU cycles but it optimizes the user’s interaction with the system.


Under what circumstances would a user be better off using a time-sharing system, rather than a personal computer or single-user workstation?

Answer

When there are few other users, the task is large, and the hardware is fast, timesharing makes sense. The full power of the system can be brought to bear on the user’s problem. The problem can be solved faster than on a personal computer. Another case is when there are lots of other users needing resources at the same time. A personal computer is best when the job is small enough to be executed reasonably on it, and when performance is sufficient to execute the program to the user’s satisfaction.


Describe the differences between symmetric and asymmetric multiprocessing. What are three advantages and one disadvantage of multiprocessor systems?

Answer

Symmetric multiprocessing treats all processors as equals, and I/O can be processed on any CPU. Asymmetric multiprocessing has one master CPU and the remainder CPUs are slaves. The master distributes tasks among the slaves, and I/O is usually done by the master only. Multiprocessors can save money, by not duplicating power supplies, housings, and peripherals. They can execute programs more quickly, and can have increased reliability. They are also more complex in both hardware and software than uniprocessor systems.


Why are distributed systems desirable?

Answer

Distributed systems can provide resource sharing, computation speedup, increased reliability, and the ability to communicate with remote sites.


What is the main difficulty that a programmer must overcome in writing an operating system for a real-time environment?

Answer

The main difficulty is keeping the operating system within the fixed time constraints of a real-time system. If the system does not complete a task in a certain time, it could cause a breakdown of the entire system it is running. Therefore when writing an operating system for a real-time system, the writer must be sure that his scheduling schemes don’t allow response time to exceed the time constraint.


22-07-2008 (13:30) από Άρης -
Αλλαγή σειρών 4-14 από:

What are the three main purposes of an operating system?

Answer

There are several possible purposes of an operating system: To provide an environment for a computer user to execute programs on computer hardware in a convenient and efficient manner. To allocate the separate resources of the computer as needed to solve the problem given. The allocation process should be as fair and efficient as possible. As a control program it serves two major functions:

  1. supervision of the execution of user programs to prevent errors and improper use of the computer, and
  2. management of the operation and control of I/O devices.
σε:

True/False: An operating system can be viewed as “resource allocator” to control various I/O devices and user programs.

Answer: True

Αλλαγή σειρών 8-21 από:

List the four steps that are necessary to run a program on a completely dedicated machine.

Answer

  1. Reserve machine time.
  2. Manually load program into memory
  3. Load starting address and begin execution
  4. Monitor and control execution of program from console.
σε:

What is the fundamental goal of computer systems?

Answer: To execute user programs and solve user problems.

Αλλαγή σειρών 12-21 από:

An extreme method of spooling, known as staging a tape, is to read the entire contents of a magnetic tape onto disk before using it. Discuss the main advantage of such a scheme.

Answer

No I/O is needed while the data is being processed, so staging is more simple than spooling. All of the data are on-line before they are needed so a process can run at full speed. The disadvantage is that more time is spent, before the process starts, in loading the data, and more disk space is consumed in storing the entire tape contents.

σε:

Define operating systems in terms of what they do.

Answer: Their primary goal is convenience of the user; the secondary goal is efficient operation and allocation of all resources.

Αλλαγή σειρών 17-22 από:

In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems.

  1. What are two such problems?
  2. Can we ensure the same degree of security in a time-shared machine as we have in a dedicated machine?

Explain your answer.

σε:

Describe how the earliest computers were used.

Answer: The programmer himself operated the computer by using switches. He had to sign up for free time.


What problems were involved in these earliest computers? Answer: The user had to guess the amount of time needed to complete his job, fairly accurately, to avoid wasting machine time, and still allow enough time to complete the job. 1.6 What software was added to increase user ef?ciency? Answer: Libraries of common functions, device drivers, assembly language, compilers. 1.7 What effect did adding I/O devices have on software? Answer: Creation of software libraries shared by all users, especially for input–output subroutines. 1.8 What factors contributed to the setup time for a job? List them. Answer: a. Load loader tape. b. Load compiler tape. c. Load source program. d. Execute compiler with output going to tape. e. Rewind each tape. f. If output of compiler was assembly language, load assembler. g. Rewind tapes. h. Execute assembler with object output to tape. i. Rewind tapes. j. Load the object program from tape. k. Execute the program with output going to paper tape. l. Run paper tape output through teletype to get printed copy. Note: On some systems, the loader had to be reloaded after many of the above steps. 1.9 What is a simple batch system? Answer: A professional computer operator (or machine) groups jobs by characteristics and runs groups of similar jobs together, ef?ciently. 1.10 Why use simple batch systems, in preference to early systems? Answer: Less setup time, and thus less idle time of the computer. 1.11 What is “automatic job sequencing”? Answer: System proceeds from one job to the next without human intervention. 1.12 Why have automatic job sequencing? Answer: To avoid the delays inherent in having the operator changing jobs, and doing things manually. 1.13 What is the purpose of the “resident monitor”? Answer: To perform orderly and ef?cient automatic job sequencing, regardless of errors that might arise. 1.14 What were control cards used for? Answer: To let monitor know what resources are needed for current job, such as compiler, linker, data, etc., when to use them, and with which ?le; and to tell monitor when it reaches end of job. 1.15 List parts of the monitor. Answer: Control card interpreter, device drivers, loader. 1.16 Compare speeds of various I/O devices, in characters/second. Answer: humans 0.5 to 5 characters/second paper tape 10 characters/second cards 1600 characters/second magnetic tape 160,000 characters/second 1.17 Describe two kinds of off-line operations. Answer: a. Cards copied to magnetic tape, which was then mounted on computer; output of computer was dumped to magnetic tape, which was then mounted for output to a printer. b. Satellite computers read cards onto magnetic tape, which could transfer information to the main computer without remounting. 1.18 Describe two approaches to off-line processing. Answer: a. Data is read from cards onto magnetic tapes, which are in turn mounted manually on the main system. Printer output from the main system is saved on magnetic tape, which is then mounted manually on a tape reader attached to a line printer. b. Data is read from cards onto magnetic tapes. But the tapes are not removed from their drives. Instead, a small computer reads them and sends the information to the main system. Similarly with output. Note: Main difference here is that data was manually exchanged between main computer and off-line system. 1.19 What is device independence? Answer: The feature of systems that allows one input device to be replaced by another without changes in the users’ programs. Similarly with output. Thus, an old model card reader can be replaced with a new model; the old device driver programs are replaced by new ones; user programs need not be changed (though they may need to be relinked). Note: Many students respond that it is the ability to use different devices. This is false. You can write a FORTRAN II program to read cards and print to a line printer, two different devices; yet this does not imply device independence. 1.20 What were the advantages of off-line operations? Answer: a. Main computer no longer constrained by speed of card reader. b. Application programs used logical I/O devices instead of physical I/O devices; programs didn’t have to be rewritten when new I/O devices replaced old ones. 1.21 How have disk systems helped solved problems inherent in off-line systems? Answer: Off-line systems use magnetic tape. The system cannot read data from one end of the tape while the card reader writes data on the other end; it takes about 5 minutes to rewind the tape fully. With disks, it takes only milliseconds to alternate from the portion of the disk used for input and the portion for output. 1.22 What is spooling? Answer: An acronym for “Simultaneous Peripheral Operation On-Line.” It uses the disk as a large buffer for outputting data to line printers and other devices (like micro?lm). It can also be used for input, but is generally used for output. Its main use is to prevent two users from alternately printing lines to the line printer on the same page, getting their output completely mixed together. It also helps in reducing idle time and overlapped I/O and CPU. 1.23 How do I/O-bound and CPU-bound programs differ? Answer: In I/O-bound programs, the CPU remains idle much of the time. In CPU-bound programs, the I/O processor remains idle. Note: I/O is never “faster” than CPU. 1.24 What is multiprogramming? Answer: In multiprogramming, several programs are in memory concurrently; the system switches among the programs for ef?cient processing, and minimal idle time. Note: Many students claim multiprogramming “always” keeps CPU and I/O devices busy; this is false; what is the computer to do at 3 AM Sunday morning, when there’s no job to run? 1.25 De?ne batch systems in terms of interaction. Answer: They are essentially devoid of interaction between user and program. All problems must be anticipated, and can’t be corrected on-line. 1.26 In what ways are batch systems inconvenient for users? Answer: Users can’t interact with their jobs to ?x problems. They must anticipate problems or else debugging could be a mess with machine-language dumps. There may also be long turnaround times. 1.27 What is time-sharing? Answer: Using scheduling and multiprogramming to provide an economical interactive system of two or more users. 1.28 What are the main advantages of a time-share system? Answer: Interaction with computer while program is running, short response times (usually less than 10 seconds). 1.29 How is time-sharing usually implemented? Answer: Each user is given a brief time-slice for her job, in round-robin fashion. Her job continues until the time-slice ends. Then her job stops, until it is her turn again. 1.30 How do MULTICS and UNIX differ? Answer: * MULTICS was a time-sharing system created on a large mainframe GE computer (since then taken over by Honeywell), by GE, by Bell Labs, and by faculty at MIT. It was very ?exible, and oriented toward programmers. * UNIX was inspired by MULTICS; but it was designed by Ritchie and Thompson in 1974 at Bell Labs for use on minicomputers, like the PDP-11. It was designed for program development, using a device-independent ?le system. 1.31 What is a multiprocessor system? Answer: A system with two or more CPUs. 1.32 What is a master/slave processor system? Answer: A master computer controls the actions of various slave computers. 1.33 What does RJE stand for? Answer: Remote Job Entry. 1.34 What is a real-time system? Answer: A system used to control a dedicated application. 1.35 How does a real-time system differ from time-share? Answer: In time-sharing, fast response is desirable, but not required. In real-time systems, processing must be completed within certain time constraints appropriate for the system. 1.36 List several examples of real-time systems. Answer: a. Control of a nuclear reactor, to prevent chain reaction. b. Control of a space ship, to avoid collision with meteors. c. Control of manufacturing equipment, such as lathes, canners, etc. d. Detecting patients’ conditions in Intensive Care Units in hospitals. e. Collecting data on cosmic rays in physics research.


What are the three main purposes of an operating system?

Αλλαγή σειρών 32-34 από:
  1. Stealing or copying one’s programs or data; using system resources (CPU, memory, disk space, peripherals) without proper accounting.
  2. Probably not, since any protection scheme devised by man can inevitably be broken by him, and the more complex the scheme, the more difficult it is to feel confident of its correct implementation.
σε:

There are several possible purposes of an operating system: To provide an environment for a computer user to execute programs on computer hardware in a convenient and efficient manner. To allocate the separate resources of the computer as needed to solve the problem given. The allocation process should be as fair and efficient as possible. As a control program it serves two major functions:

  1. supervision of the execution of user programs to prevent errors and improper use of the computer, and
  2. management of the operation and control of I/O devices.
Διαγραφή σειράς 36:
Αλλαγή σειρών 39-40 από:

What is the main advantage of multiprogramming?

σε:

List the four steps that are necessary to run a program on a completely dedicated machine.

Αλλαγή σειρών 45-46 από:

Multiprogramming makes efficient use of the CPU by overlapping the demands for the CPU and its I/O devices from various users. It attempts to increase CPU utilization by always having something for the CPU to execute.

σε:
  1. Reserve machine time.
  2. Manually load program into memory
  3. Load starting address and begin execution
  4. Monitor and control execution of program from console.
Αλλαγή σειρών 54-55 από:

What are the main differences between operating systems for mainframe computers and personal computers?

σε:

An extreme method of spooling, known as staging a tape, is to read the entire contents of a magnetic tape onto disk before using it. Discuss the main advantage of such a scheme.

Αλλαγή σειρών 60-61 από:

Personal computer operating systems are not concerned with fair use, or maximal use, of computer facilities. Instead, they try to optimize the usefulness of the computer for an individual user, usually at the expense of efficiency. Consider how many CPU cycles are used by graphical user interfaces (GUIs). Mainframe operating systems need more complex scheduling and I/O algorithms to keep the various system components busy.

σε:

No I/O is needed while the data is being processed, so staging is more simple than spooling. All of the data are on-line before they are needed so a process can run at full speed. The disadvantage is that more time is spent, before the process starts, in loading the data, and more disk space is consumed in storing the entire tape contents.

Διαγραφή σειράς 62:
Αλλαγή σειρών 65-66 από:

Define the essential properties of the following types of operating systems: Batch Interactive Time sharing Real time Distributed.

σε:

In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems.

  1. What are two such problems?
  2. Can we ensure the same degree of security in a time-shared machine as we have in a dedicated machine?

Explain your answer.

Πρόσθεση σειρών 74-110:
  1. Stealing or copying one’s programs or data; using system resources (CPU, memory, disk space, peripherals) without proper accounting.
  2. Probably not, since any protection scheme devised by man can inevitably be broken by him, and the more complex the scheme, the more difficult it is to feel confident of its correct implementation.

What is the main advantage of multiprogramming?

Answer

Multiprogramming makes efficient use of the CPU by overlapping the demands for the CPU and its I/O devices from various users. It attempts to increase CPU utilization by always having something for the CPU to execute.


What are the main differences between operating systems for mainframe computers and personal computers?

Answer

Personal computer operating systems are not concerned with fair use, or maximal use, of computer facilities. Instead, they try to optimize the usefulness of the computer for an individual user, usually at the expense of efficiency. Consider how many CPU cycles are used by graphical user interfaces (GUIs). Mainframe operating systems need more complex scheduling and I/O algorithms to keep the various system components busy.


Define the essential properties of the following types of operating systems: Batch Interactive Time sharing Real time Distributed.

Answer

Αλλαγή σειρών 117-180 από:
σε:

We have stressed the need for an operating system to make efficient use of the computing hardware. When is it appropriate for the operating system to forsake this principle and to “waste” resources? Why is such a system not really wasteful?

Answer

Single-user systems should maximize use of the system for the user. A GUI might “waste” CPU cycles but it optimizes the user’s interaction with the system.


Under what circumstances would a user be better off using a time-sharing system, rather than a personal computer or single-user workstation?

Answer

When there are few other users, the task is large, and the hardware is fast, timesharing makes sense. The full power of the system can be brought to bear on the user’s problem. The problem can be solved faster than on a personal computer. Another case is when there are lots of other users needing resources at the same time. A personal computer is best when the job is small enough to be executed reasonably on it, and when performance is sufficient to execute the program to the user’s satisfaction.


Describe the differences between symmetric and asymmetric multiprocessing. What are three advantages and one disadvantage of multiprocessor systems?

Answer

Symmetric multiprocessing treats all processors as equals, and I/O can be processed on any CPU. Asymmetric multiprocessing has one master CPU and the remainder CPUs are slaves. The master distributes tasks among the slaves, and I/O is usually done by the master only. Multiprocessors can save money, by not duplicating power supplies, housings, and peripherals. They can execute programs more quickly, and can have increased reliability. They are also more complex in both hardware and software than uniprocessor systems.


Why are distributed systems desirable?

Answer

Distributed systems can provide resource sharing, computation speedup, increased reliability, and the ability to communicate with remote sites.


What is the main difficulty that a programmer must overcome in writing an operating system for a real-time environment?

Answer

The main difficulty is keeping the operating system within the fixed time constraints of a real-time system. If the system does not complete a task in a certain time, it could cause a breakdown of the entire system it is running. Therefore when writing an operating system for a real-time system, the writer must be sure that his scheduling schemes don’t allow response time to exceed the time constraint.


22-07-2008 (13:19) από Άρης -
Πρόσθεση σειρών 1-95:

Εισαγωγή στα Λειτουργικά Συστήματα

What are the three main purposes of an operating system?

Answer

There are several possible purposes of an operating system: To provide an environment for a computer user to execute programs on computer hardware in a convenient and efficient manner. To allocate the separate resources of the computer as needed to solve the problem given. The allocation process should be as fair and efficient as possible. As a control program it serves two major functions:

  1. supervision of the execution of user programs to prevent errors and improper use of the computer, and
  2. management of the operation and control of I/O devices.

List the four steps that are necessary to run a program on a completely dedicated machine.

Answer

  1. Reserve machine time.
  2. Manually load program into memory
  3. Load starting address and begin execution
  4. Monitor and control execution of program from console.

An extreme method of spooling, known as staging a tape, is to read the entire contents of a magnetic tape onto disk before using it. Discuss the main advantage of such a scheme.

Answer

No I/O is needed while the data is being processed, so staging is more simple than spooling. All of the data are on-line before they are needed so a process can run at full speed. The disadvantage is that more time is spent, before the process starts, in loading the data, and more disk space is consumed in storing the entire tape contents.


In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems.

  1. What are two such problems?
  2. Can we ensure the same degree of security in a time-shared machine as we have in a dedicated machine?

Explain your answer.

Answer

  1. Stealing or copying one’s programs or data; using system resources (CPU, memory, disk space, peripherals) without proper accounting.
  2. Probably not, since any protection scheme devised by man can inevitably be broken by him, and the more complex the scheme, the more difficult it is to feel confident of its correct implementation.

What is the main advantage of multiprogramming?

Answer

Multiprogramming makes efficient use of the CPU by overlapping the demands for the CPU and its I/O devices from various users. It attempts to increase CPU utilization by always having something for the CPU to execute.


What are the main differences between operating systems for mainframe computers and personal computers?

Answer

Personal computer operating systems are not concerned with fair use, or maximal use, of computer facilities. Instead, they try to optimize the usefulness of the computer for an individual user, usually at the expense of efficiency. Consider how many CPU cycles are used by graphical user interfaces (GUIs). Mainframe operating systems need more complex scheduling and I/O algorithms to keep the various system components busy.


Define the essential properties of the following types of operating systems: Batch Interactive Time sharing Real time Distributed.

Answer

  1. Batch. Jobs with similar needs are batched together and run through the computer as a group by an operator or automatic job sequencer. Performance is increased by attempting to keep CPU and I/O devices busy at all times through buffering, off-line operation, spooling, and multiprogramming. Batch is good for executing large jobs that need little interaction; it can be submitted and picked up later. Answers to Exercises.
  2. Interactive. Composed of many short transactions where the results of the next transaction may be unpredictable. Response time needs to be short (seconds) since the user submits and waits for the result.
  3. Time sharing.Uses CPU scheduling and multiprogramming to provide economical interactive use of a system. The CPU switches rapidly from one user to another. Instead of having a job defined by spooled card images, each program reads its next control card from the terminal, and output is normally printed immediately to the screen.
  4. Real time. Often used in a dedicated application. The system reads information from sensors and must respond within a fixed amount of time to ensure correct performance.
  5. Distributed. Distributes computation among several physical processors. The processors do not share memory or a clock. Instead, each processor has its own local memory. They communicate with each other through various communication lines, such as a high-speed bus or telephone line.

Τελευταία ενημέρωση: 26-08-2008 (11:31)

Copyright 2008 - Άρης Φεργάδης