Free GCSE Computer Science Questions and Answers

The full-mark answer · 5 marks

The list is divided in half repeatedly until each list contains one item, because a one-item list is already sorted. Lists are then merged back in pairs: the front items of the two lists are compared and the smaller is moved into the new list, repeating until both are empty. So 8 and 3 merge to 3, 8; 5 and 1 merge to 1, 5; and merging those compares 3 with 1, then 3 with 5, then 8 with 5, giving 1, 3, 5, 8.

The full-mark answer · 4 marks

50 is the boundary between fail and pass, so the program’s behaviour changes there. 49 and 51 test immediately either side of it and 50 tests the boundary itself, which is the value that exposes a wrong comparison operator — a program using > rather than ≥ passes 51 and fails 50. 0 is a valid extreme, testing the lowest input the program should accept.

The full-mark answer · 2 marks

A constant is a named value that is set when the program is written and cannot be altered while it runs. One reason for using one is that a value used in many places is defined once, so a change to it is a single edit and cannot be applied inconsistently.

The full-mark answer · 4 marks

Read a password, then repeat while its length is below eight, reading a replacement each time. The loop ends only when a password of eight or more characters has been entered.

The full-mark answer · 2 marks

128 + 64 = 192, and 200 − 192 = 8, so the 8 column is set: 11001000.

The full-mark answer · 2 marks

One hexadecimal digit represents exactly four binary digits, so an eight-bit value is written as two characters rather than eight. It is therefore much shorter to write, quicker to read and far less error-prone to copy, and because the grouping is exact the conversion needs no calculation.

The full-mark answer · 2 marks

The control unit decodes each instruction fetched from memory and sends control signals to the other components of the CPU and to memory, coordinating their operation so the instruction is carried out.

The full-mark answer · 4 marks

During the execute stage the accumulator holds the data currently being operated on and receives the result the ALU produces. Because it sits inside the CPU, that result is immediately available to the next instruction, which is far faster than writing it out to main memory and reading it back.

The full-mark answer · 3 marks

A LAN connects devices across a single site, such as one school or office, and the organisation normally owns the connecting hardware itself. A WAN connects devices across a wide geographical area, potentially between countries, and uses infrastructure owned and managed by third parties such as telecommunications companies.

The full-mark answer · 4 marks

A router connects two or more separate networks — typically a home or office LAN to the internet. It receives data packets, reads the destination IP address in each one, and forwards the packet along the most appropriate route towards that destination.

The full-mark answer · 1 mark

Malware is malicious software: any program written with the deliberate intention of damaging or disrupting a computer system, or of gaining unauthorised access to it or to the data it holds.

The full-mark answer · 2 marks

Discarded machines become electronic waste containing toxic materials such as lead and mercury, which can contaminate soil and water where they are not properly recycled. And manufacturing each replacement consumes energy, water and mined raw materials, including rare earth elements extracted at environmental cost.