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1. The children climbed under/over the wall to escape from the angry gardener.
2. She walked quickly past/along the shops without looking in the windows.
3. The current is very strong. It would be dangerous to swim through/across this river.
4. She got dressed quickly and ran up/down the stairs to the kitchen.
5. Fiona is going to come to the party by/in her car.
6. I saw a man walking from/towards me smiling, but I didn't recognize him.
7. We tried to push our way through/towards the crowds to see our favorite singer.
8. There was no way to cross the lake, so we had to walk through/round it.
9. The boy got over/out of bed and went to the window.
10. I put the bags onto/into the table, then I put the shopping away.
11. You will see the post office on your right when you go through/round the corner.
12. She looked along/into her crystal ball and told the girl her fortune.
WRITING/SPEAKING
Think about advantages and disadvantages of using a desktop computer, a laptop and a palm computer. Compare them.
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UNIT 5
OPERATING SYSTEM
Vocabulary Bank Unit 5
Task 1. Read, write the translation and learn the basic vocabulary terms:
1. abbreviation
2. accommodation
3. additional
4. application program
5. applications software
6. assembly line
7. background
8. batch
9. circumstance
10. command driven
11. command prompt
12. commitment
13. computation
14. environment
15. eye-watering price
16. facility
17. graphic engine
18. graphical user interface
19. icon ( n )
20. interaction
21. interface
22. kernel
23. key function
24. layer
25. logout
26. memory-protection
27. multiple
28. multiprogramming
29. multi-tasking mainframe
30. multi-user
31. resident program
32. revenue stream
33. robust
34. search engine
35. shell
36. shortcoming
37. source code
38. sufficient
39. supervisor program
40. to be aware
41. to establish
42. to facilitate
43. to implement
44. to invoke
45. to object to
46. to adopt
47. to allocate
48. to boot
49. to entail
50. to hack into
51. to interrupt
52. to lock
53. to look forward to
54. typesetting tool
TEXT 5A. OPERATING SYSTEMS
Some operating systems are command driven (i.e. the user runs a program by typing a command). The screen is usually blank except for a symbol which acts as a command prompt. When the command is typed at the prompt and the Enter key is pressed, the command is processed and the output is displayed on the screen. OS commands are usually short words or abbreviations (e.g., date, logout, password, Is).
Unix is a command driven operating system used on all sizes of computers, but mostly large multi-user, multi-tasking mainframe computers. It is available in many versions, such as Linux, Minix etc.
Operating Systems: Hidden Software
When a brand new computer comes off the factory assembly line, it can do nothing. The hardware needs software to make it work. Are we talking about applications software such as wordprocessing or spreadsheet software? Partly. But an applications software package does not communicate directly with the hardware. Between the applications software and the hardware is a software interface - an operating system. An operating system is a set of programs that lies between applications software and the computer hardware.
The most important program in the operating system, the program that manages the operating system, is the supervisor program, most of which remains in memory and is thus referred to as resident. The supervisor controls the entire operating system and loads into memory other operating system programs (called non-resident) from disk storage only as needed.
An operating system has three main functions: (1) manage the computer's resources, such as the central processing unit, memory, disk drives, and printers, (2) establish a user interface, and (3) execute and provide services for applications software. Keep in mind, however, that much of the work of an operating system is hidden from the user. In particular, the first listed function, managing the computer's resources, is taken care of without the user being aware of the details. Furthermore, all input and output operations, although invoked by an applications program, are actually carried out by the operating system. Some operating systems have a GUI (pronounced like 'goo-ey' – graphical user interface) that allows the user to use a mouse to click on icons on the screen or choose commands from a list of choices known as a menu. Operating systems with graphical interfaces mentioned in this unit include: MacOS, OS/2, Penpoint, Windows NT, Windows 3.x, Windows 9X and Windows 2000.
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.
Дата публикования: 2015-09-17; Прочитано: 1638 | Нарушение авторского права страницы | Мы поможем в написании вашей работы!