General Features of Operating Systems

An operating system is a master control program which controls the functions of the computer system as a whole and the running of application programs. All computers do not use the same operating systems. Some software being only designed to run under the control of specific operating systems, it is important to assess the operating system used on a particular model before initial commitment. Some operating systems are adopted as “industry standards” and these are the ones which should be evaluated because they normally have a good software base. The reason for this is that software houses are willing to expand resources on the development of application packages for machines functioning under the control of an operating system which is widely used. The cost of software could be lower in such circumstances as the development costs are spread over a greater number of users, both actual and potential.

Mainframe computers usually process several application programs concurrently switching from one to the other for the purpose of increasing processing productivity. This is known as multiprogramming (multi-tasking in the context of microcomputers), which requires a powerful operating systems incorporating work scheduling facilities to control the switching between programs. This entails that data are read for one program while the processor is performing computations on another and printing out results on yet another.

In multi-user environments an operating system is required to control terminal operations on a shared access basis as only one user can access the system at any moment of time. The operating system allocates control to each terminal in turn. Such systems also require a system for record locking and unlocking, to prevent one user attempting to read a record whilst another user is updating it, for instance. The first user is allocated control to write to a record (or file in some instances) and other users are denied access until the record is updated and unlocked.

Some environments operate in concurrent batch and real-time mode. This means that a “background” job deals with routine batch processing whilst the “foreground” job deals with real-time operations such as airline seat reservations, on-line booking of hotel accommodation, or control of warehouse stocks, etc. The real-time operation has priority, and the operating system interrupts batch processing to deal with real-time inquiries or file updates. The stage of batch processing attained at the time of the interrupt is temporarily transferred to backing storage. After the real-time operation has been dealt with, the interrupted program is transferred back to internal memory from backing storage. And processing recommences from a “restart” point.

The operating system also copies to disk backing storage the state of the real-time system every few minutes (periodic check points) to provide a means of recovering the system in the event of a malfunction.

An operating system is stored on disk and has to be booted into the internal memory (RAM) where it must reside throughout processing so that commands are instantly available. The operating system commands may exceed the internal memory capacity of the computer in which case only that portion of the OS which is frequently used is retained internally, other modules being read in from disk as required. Many microcomputers function under the control of a disk operating system known as DOS.

Task 2. Answer the following questions.

1. What is an operating system? 2. What system provides an interface between applications programs and the computer hardware? 3. Is the work of the operating system always obvious to the user? 4. What is the most important program in an OS? 5. How does the supervisor program work? 6. What is the difference between resident and non-resident programs? 7. How can you explain the meaning “command driven”? 8. What is a command prompt? 9. How can you define Unix? What versions is it available in? 10. What do you know about GUI? 11. What are three main functions of an operating system? Give some examples to prove your answer. 12. Why is it important to assess the operating system on a computer before buying it? 13. What is multiprogramming?

Task 3. Give the Ukrainian equivalents for:

load, available, multi-tasking computer, user, user interface, word processor, non-resident programs, command-driven, execute, abbreviations, multi-user mainframe computer, printing files, blank, graphical user interface.

Task 4. Find the English equivalents for the following word combinations.

1. командний рядок, підказка; 2. прикладні програми; 3. текстовий процесор; 4. електронні таблиці; 5. операційна система; 6. пакет програм; 7. резидентна програма; 8. керуюча програма, програма розпорядник; 9. великі комп'ютери; 10. піктограми; 11. натиснути і відпустити клавішу; 12. апаратне забезпечення комп'ютера

Task 5. Mark the following as True or False.

1. The work of the operating system takes place in the background and is always obvious to the user. 2. The most important in an OS is the supervisor program. 3. Programs that remain in memory while the computer is in use are known as non-resident programs. 4. The screen is usually blank except for a symbol (e.g.$) which acts as a command prompt. 5. OS commands are usually long words. 6. Unix is a command driven operating system used in all sizes of computer but mostly large multi-user, multi-tasking mainframe computers. 7. The hardware doesn’t need software to make it work. 8. An application software package communicates directly with the hardware. 9. An operating system has only two main functions.

Task 6. Match the terms in Table A with the statements in Table B.

Table A

Table B

1. operating system 2. interface 3. applications (program or software) 4. Unix 5. menu 6. spreadsheet 7. swipe card 8. word processor 9. software package

The hardware or software that connects two systems and allows them to communicate with each other. A popular multi-user multi-tasking operating system originally designed for mainframe computers. A wide variety of versions exist. The set of programs that controls the basic functions of a computer and provides communication between the application programs and the hardware. A computer program designed to be used for a particular purpose, e.g. a wordprocessor, spreadsheets or database program. A type of application program with an array of cells that is used for calculating formulas. A list of options displayed on a computer screen. An application program or collection of programs that can be used in different ways. A type of computer application program used for typing and editing text documents. A plastic card with a magnetic strip running across it containing confidential data.

Task 7. Fill in the blanks with the words from the box.

interface, supervisor, manage, memory, package, software, drives, interface, nonresident, command driven

1. An applications software ____ does not communicate directly with the hardware. 2. Between the applications software and the hardware is a software _____ – an operating system. 3. The most important program in the operating system is the _____ program, most of which remains in memory. 4. An operating system has three main functions: 1) ____ the computer resources, such as the central processing unit, ____, disk ____ and printers, 2) establish a user _____ , and 3) execute and provide services for applications _____ . 5. Unix is a ____ operating system used in all sizes of computers. 6. Programs that only stay in memory while they are being used are known as _____ programs.

Task 8. Complete the gaps in this summary of the text on operating systems using these linking words and phrases.

although because in addition such as but therefore

The user is aware of the effects of different applications programs ____ operating systems are invisible to most users. They lie between applications programs, ____ wordprocessing, and the hardware. The supervisor program is the most important. It remains in memory, _____ it is referred to as resident. Others are called non-resident ____ they are loaded into memory only when needed. Operating systems manage the computer's resources, _____ the central processing unit . ______ , they establish a user interface, and execute and provide services for applications software. ______ input and output operations are invoked by applications programs, they are carried out by the operating system.

Task 9. Here is a list of typical tasks performed by an operating system. In each case the main verb has been omitted. Fill in the blanks using the words a) execute, b) monitor, c) format, d) diagnose. Sometimes more than one may apply

A typical operating system will:

1. _________ input and output devices.

2. _________ the status of hardware devices.

3. _________ hardware interrupts.

4. _________ new disks.

5. _________ disk directories.

6. _________ disk reading and writing operations.

7. _________ disk errors.

8. _________ disk commands relating to the deletion, copying, renaming, and dumping of files.

Task 10. Problem-solving: try to find the commands from the lists below which will have these actions.