Computer Science As Level Ocr Model Answers

Front 1

State what is meant by the term real-time [1 mark]

Back 1

The system gives a response within a guaranteed timeframe

Front 2

Explain two advantages of the monitoring system having its operatingsystem stored in ROM

Back 2

1. ROM is quick to start up so the system can bestarted up quickly

2. ROM cannot be altered so there is no chanceof the OS being accidentally or maliciouslychanged

Front 3

Describe what happens to the contents of RAMand ROM when power to the monitoring system is removed.

Back 3

The contents of RAM are wiped (1) whereasthe contents of ROM remain the same (1)

Front 4

Advantages of Peer-to-Peer networks for a business [2 marks]

Back 4

Peer to peer means there isn’t a reliance on thecompany’s server (1) and its connection to theInternet (1).

OR

This means it hasn’t got to invest in lots ofhardware and bandwidth (1) and the system islikely to be more fault tolerant (1).

Front 5

Describe why 'Name' is not a suitable primary key. [2 marks]

Back 5

A primary key must have a unique value foreach record. The name of something/someone may occur twice.

Front 6

What is the purpose of a secondary key?

Back 6

To be indexed to therefore allow faster searching by the user.

Front 7

Describe what is meant by the term JavaScript? [2 Marks]

Back 7

A programming language that runs in a webbrowser (1) that can be embedded into HTML(1)

......

with

Front 8

Why is JavaScript likely to be interpreted rather than compiled? [2 marks]

Back 8

JavaScript is likely to be run on a variety ofmachines (1) with differentprocessors/architectures (1)

Front 9

Describe what is meant by a utility? [2 Marks]

Back 9

A utility performs a specific task (1) and is usuallyrelated to the upkeep of the system (1).

Front 10

Describe one advantage of storing the CSS in an external file rather than it beingembedded within HTML files. [3 Marks]

Back 10

Content and formatting are kept separate (1).Changes can be made to the external style sheetand affect the whole site (1) saving time (1)

Front 11

What is a primary key? [2 marks]

Back 11

A field that has a unique value/a unique identifier(1) for every record in that table (1)

Front 12

Explain why flash storage would be moreappropriate than a magnetic hard drive for a portable device? [3 Marks]

Back 12

Device is likely to undergo lots of suddenmovement (1) magnetic hard drives canbe susceptible to damage if moved around (1) whereas flash memory hasno moving parts and so is not affected (1).

Front 13

Describe two functions an operating system might be expected to carry out [4 Marks]

Back 13

Control hardware (1) such as graphicscard, input devices, storage etc. (1)

Provide a user interface (1) for the user to perform tasks (1)

Front 14

Describe what is meant by a LAN [2 marks]

Back 14

A group of computers/devices (1)connected over a small geographical area (1)

Front 15

TCP/IP uses packet switching.Explain what is meant by packet switching. [4 Marks]

Back 15

Data is split into chunks called packets (1) which have labels (1). Each packet is sent on the mostconvenient/avoidable route (1) meaningthey may arrive in a different order to whichthey were sent (1)

Front 16

State two differences between RAM and ROM in a typical PC computer system [2 Marks]

Back 16

-RAM is volatile/ROM is not volatile

-RAM is editable/ROM cannot be altered

Front 17

State one item that needs to be stored in RAM and give a reason why RAM is used. [2 Marks]

Back 17

- User files/software/OS currently in use

-computer needs access tosoftware but needs to be able to replace it

Front 18

State one item of software that is stored in ROM and give a reason why ROM is necessary. [2 marks]

Back 18

-Boot file/program/BIOS

-Must be available when computer switched on ( therefore must bestored on medium which is non-volatile)

Front 19

Explain the need for the Program Counter (PC) Register. [2 Marks]

Back 19

-Is needed to store the address of the next instruction (to beprocessed)

-Value is then sent to the MAR

Front 20

Explain the need for the Memory Address Register (MAR). [2 Marks]

Back 20

-Contains the address of the instruction (to be accessed in memory)…

- as sent from the PC.

Front 21

Explain the need for the Memory Data Register (MDR). [2 Marks]

Back 21

Contains the instruction which has been accessed from memory. That is referenced by the MAR.

Front 22

What is meant by a protocol?

Back 22

A set of rules (1) to govern data transmission (1)

Front 23

Describe a command line interface and state why it is used. [3 marks]

Back 23

Commands are typed in (to the system) (1) at the (screen) prompt (1) and allows access to all areas of the system (1)

Front 24

State two advantages of having a LAN instead of a set of stand-alone machines. [2 marks]

Back 24

Allows the devices to communicate with each other (1) and share peripheral devices/software/data (1)

Front 25

Explain what is meant by the character set of a computer [2 Marks]

Back 25

Normally equates to the symbols on a keyboard/digits/letters (1) that can be interpreted by a computer (1)

Front 26

Explain how codes are used to represent a character set [3 marks]

Back 26

Each symbol has a binary code (1) which is unique (1). E.g. ASCII/Unicode (1)

Front 27

Name and Describe THREE buses that are used to convey information between the special registers. [6 marks]

Back 27

- Control bus (1) - transmits control signals from the control unit (to other parts of theprocessor)(1)

- Data bus (1) - carries the data (from one place to another) (1)

- Address bus (1) - carries the location address (register) of where the data is going (1)

Front 28

State what is meant by a distributed system [1 mark]

Back 28

A system which shares processing (between the processors on anetwork)

Front 29

Explain two facilities of a network operating system. [4 marks]

Back 29

- File handling (1) - allowing Access to, and manipulation of, files dependent on theidentity of the user. (1)

- Handling communication (1) - controls the movement of data around the network (by use ofagreed protocol) (1)

Front 30

SCENARIO: A SALES DEPARTMENT

State two types of generic application software and what they are used for [4 marks]

Back 30

- Presentation software - to design and show slideshows to audiences (2)

- Database - to store details of customers. (2)

Front 31

Describe what is meant by Unicode [2 Marks]

Back 31

UNICODE is a coding system that assigns a unique code (1) to all the possible symbols available throughout the world (1)

Front 32

Describe the purpose of the ALU [3 marks]

Back 32

- Carries out arithmetic operations/calculations

- Carries out logical instructions/decisions

- Acts as a I/O gatewayto the processor.

Front 33

Define the term storage device [2 marks]

Back 33

A piece of hardware (1) that stores data electronically (1)

Front 34

Describe what is meant by Applications Packages [2 marks]

Back 34

Applications packages allow the user to do something useful (1) such as a word processor which allows the processing of documents. (1)

(2nd mark is given for any suitable example)

Front 35

Describe a single-user, multi-tasking operating system [2 Marks]

Back 35

- Only one user can use the system at one time.

- Multiple tasks can be carried out simultaneously.

Front 36

Define Hardware [1 mark]

Back 36

Physical parts of a system.

Front 37

Define Software [1 mark]

Back 37

instructions/code/programs

Front 38

Describe the characteristics of a WAN (Wide Area Network) [2 marks]

Back 38

- Computers are based remotely (1)

- typically each computer will have its ownperipherals rather than sharing them (1)

Front 39

State the purpose of an input device [1 mark]

Back 39

Allows data to be given [to the computer].

Front 40

State the purpose of an output device [1 mark]

Back 40

Reports the results of processing from the computer [tothe user].

Front 41

Define buffer. [1 mark]

Back 41

A small area of computer memory

Front 42

Define interrupt [1 mark]

Back 42

A signal or message sent to the processor which stops thecurrent activity of the processor.

Front 43

NOTE

Back 43

NOTE: THESE QUESTIONS WILL OFTEN BE GIVEN A SCENARIO WHICH SHOULD BE APPLIED TO THE MODEL ANSWER.

Front 44

Explain why ___ would use a distributed OS? [2 marks]

Back 44

Allow multiple computers/resources [1] to be treated as one (so can work on the same problem) [1]

NOTE: usually a 3 marker. apply to scenario.

Front 45

How does a fast clock speed improve the processor's performance? [2 marks]

Back 45

Gives more cycles per second

More instructions can be executed per second

Front 46

How does a large cache memory improve the processor's performance [2 marks]

Back 46

More space for data/instructions in cache memory.

RAM needs to be accessed less frequently.

(Accessing cache is quicker than accessing the RAM)

Front 47

Explain the automated process that takes place that allows customers to access the site when they enter the domain name into their browser [3 marks]

Back 47

Domain name is entered and is sent to the DNS servers.

DNS servers map the domain to an IP address.

DNS Server sends the IP address to browser.

Front 48

Explain how the web developer would implement ____. You are not expected to write any code. [4 marks]

Back 48

1. State language - why. (JS which allows dynamic content)

2. When this happens... (language) is executed.

3. Result

4. What happens to previous...

Front 49

Describe what the instruction BRP does. [2 Marks]

Back 49

The program flow jumps to a (designated) label/another point in the program

If the value in the accumulator is positive.

Front 50

Describe what is meant by the term ‘open source software’. [2 Marks]

Back 50

Source code is freely available…

...for others to amend/examine/recompile

Front 51

Describe what is meant by the term ‘lossy compression’ [2 Marks]

Back 51

(An algorithm that) makes a file storage space/ size smaller …

... but accuracy with which it represents data is reduced/information is lost in the process.

Front 52

State why a programmer might choose to declare a variable as a floating point number. [1 Mark]

Back 52

The variable may need to store decimal numbers.

To store very large/small values.

Front 53

State what the printers’ RAM is used for. [1 Mark]

Back 53

Storing documents being/waiting to be printed.