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Cambridge University Press 2011

4 Systems andcommunications

Answers to Revision questions: 4 Systems & communications 1Cambridge IGCSE Computer Studies

Below each answer there is a page reference for the coursebook. Tis is there to help you focus

your revision. If you nd that you get an answer wrong, you can use this guide to return to the

coursebook to revise the areas that need some extra attention. Please notethese are example

answers only and do notrepresent the only possible answers.

1 An operating system is a set of programs and data les that manages a computers hardware

and the other programs that run on the computer. It controls the peripheral devices, allocates

memory between application programs, performs housekeeping tasks on the backing storage,

shares the processor between application programs.See Functions of an operating system on page 93.

2 a A command line interface requires the user to type commands at a keyboard. Te user

needs to remember the commands (although help is usually available) and the string

of options can be complex to get right. Only one command (program) at a time can

be executed.

b A graphical user interface enables the user to use a pointing device to select commands and

options from menus. Several programs can be open in various windows.

See User interface on page 98.

3 a A graphical user interface uses windows, icons, menus and a pointing device.

b In the future, user interfaces may use voice commands or gestures to control the computer.

See User interface on page 98.

4

See File management on page 101.

Disk

C:\

Folders Files and sub-folders

Programs

My Documents

Letter 2011-Jan.doc

Photos

Homework

Recycle Bin

France 2010

John birthday

Hampton Court

timetable.doc

tudors.doc

IC survey.xls

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Cambridge University Press 2011 Answers to Revision questions: 4 Systems & communications 2Cambridge IGCSE Computer Studies

5 A le manager enables the user to print, copy, move and list les.

See File management on page 101.

6 a A buffer is an area of memory that holds data temporarily ready to be sent to a program or

peripheral device.

b A peripheral device is a device that links to the processor, such as a printer, a monitor or

a webcam. (See page 93 and glossary.)c An interrupt is a signal from a peripheral device or a program to the processor asking for

some service (e.g. a printer may send an interrupt to ask for more data).

d Polling is a process in which the processor asks each peripheral device in turn if it needs

a service.

e Handshaking is a process in which a peripheral device and the processor (or two computers

on a network) establish communication.

See Peripheral device control on page 102.

7 Te operating system handshakes with the peripheral device (e.g. a printer) to establish initial

communication. Te printer driver lls the print buffer and requests the host controller to sendthe data to the printer. When the printer has dealt with the data, it tells the driver to ll the

buffer again. Tis means that data is not sent too quickly and does not get lost.

See Peripheral device control on page 104.