A backup is a copy of data that can be used if the original data is lost.

Job scheduling/Process scheduling                                                                                              (2mks)

• Operating systems allocate tasks/processes/jobs to the CPU using priority and FIFO principle

 Memory management                                                                                                                  (2mks)

• OS allocates and de-allocates memory spaces to processes loaded into the RAM
• Swaps processes between main memory and virtual memory created in the secondary storage

Taking a four-digit 0  binary number i.e (0000)2

In ones complement this is  1111

In twos complement this becomes 1111+1= 0000

So, It is clear that 0 and negative zero is the same in twos complement while in ones complement they are two different values

• switches can send and receive data simultaneously - they are full duplex
• a hub is half duplex- only one host can communicate at a time.
• a hub broadcast signals to all computers connected in a network while a switch directs data to its intended destination

(a) One from:

• Background checks
• Access control
• Physical security
• User policies

(b) To prevent unauthorised access (1) so that data remains confidential (1) by making it unintelligible (1) because it is scrambled (1)

(a)State what is meant by the terms:

Parallel data transmission

• 8 bits/1 byte/multiple bits sent at a time  
• using many/multiple/8 wires/lines

Serial data transmission

• one bit sent at a time over a single wire

• An agreement / set of rules / standard for how computers should communicate or how data is sent/received/transmitted on a network
• Example of what could be agreed in the protocol (e.g. speed / error checking / etc.)

Dual input of data

• Two inputs are compared by the system and any discrepancies are reported (and not stored.)
• Data input once, either printed out or checked on the screen and  errors corrected

 Rules are given to the processor

• Only accept A, B, C, D, E, F, G i.e Any other input rejected.

Drop-down list/radio buttons

• Provides only valid inputs, so no other validation is required

• Network operating systems
• Protocols

The organisation of files is in a hierarchy/tree structure
A node is either a folder/directory/sub-folder/sub-directory or the file itself
The top node/folder/directory/drive is the root

(a)

• Hardware required by each computer to connect to a network is a Network Interface Card / NIC / network adapter

(b)

• Computer A adds computer D’s address to packet
• Computer A sends packet to switch
• Switch looks at address on packet  Switch compares to stored list of addresses on network
• Switch forwards packet to computer D’s address

method of transmission e.g

• blue tooth
• radio
• optical
• satellite
• infra-red
• microwave

device e.g.

• 3G (WAP) mobile phones/mobile phones/cell phone/remote
• key pad/remote control/keyboard
• infra-red mouse
• multimedia mobile handsets/notebooks
• GPRS (general packet radio service) mobiles
• WLAN(or WiFi) hotspots sited in public areas - e.g. coffee
• shops, railway stations, airports, motorway services
• linked printers
• PDA's (personal digital assistants)
• GPS

• connects different networks
• transfer data packets from source to destination
• allow hosts on different networks to communicate

– knowledge base
– rule(s) base
– inference engine
– explanation system
– (expert system) shell

• user changes his mind
• new government legalisation/company policy company changes
• changes in hardware
• changes in software/upgrades/new versions
• improved operating efficiency/ease of use

• Computer viruses
• Unstable power supply
• Hard disk crash
• Theft of data/programs

• Used to resize the image
• Used to rotate the image
• Used to move the image

Blackout: This is unexpected discontinuation of power supply in the laboratory.

Power sag: Sudden drop of voltage levels that lasts less than a second.

Transients/ surge: High voltage flowing.

Brownout: Partial blackout where there's low voltage flow.

(a) State two items of data that are stored on the barcode.

• check digit
• product number/item number/code
• country of origin
• manufacturers number/code
• weight
• price

(b) Describe how the computer system checks that the barcode has been read correctly.

• check digit calculation is performed on the check digit, remainder = 0 if the barcode has been read correctly
• weights and modulus 11 and use remainder
• or subtractions and addition and use answer

(c) State the type of file access that is used to get the price from the central computer.

• random/direct/online

(d) Explain how the system updates the file when an item has been sold.

• search file/master file using barcode number/product code and decrease number in stock/increase quantity sold

• where the new system is completely different from the old one
• if there has been extensive testing of the system and the system analyst has confidence in its functionality
• If the system is not critical