Edexcel GCSE Computer Science (1CP2) Exam Questions

Award one mark for any of the following up to a maximum of one mark:

• Breaks messages/data into packets (1)
• Reassembles packets (at the destination) (1)
• Detects errors (1)
• Resends lost/missing packets/requests retransmission of lost packets (1)
• Creates/establishes a connection between two computers/hosts/sets up a connection before data is sent (1)

Do not accept routing packets or using IP addresses, which is the role of IP.

Do not accept encrypting data or providing security.

Do not accept vague answers such as 'transmits data' or 'sends data' without saying how TCP does this.

Award up to two marks for a linked description such as:

• During fetch, the program counter holds the address of the next instruction (1) which is used to fetch that instruction from main memory/RAM (1)
• During fetch, the instruction is held in a register/current instruction register (1) so the control unit can decode it (1)
• During decode, the control unit decodes the instruction held in a register/current instruction register (1) to identify the operation/operand to be carried out (1)
• During execute, a register/accumulator holds the data being operated on (1) and stores the result from the ALU (1)
• During execute, a register holds the result of an ALU operation (1) before it is written back to main memory/RAM (1)

Accept other correctly named registers (program counter/PC, current instruction register/CIR, memory address register/MAR, memory data register/MDR, accumulator) where their role is linked to a stage of the fetch-decode-execute cycle.

Do not accept 'registers store data' or 'registers hold data' on its own, without a link to fetch, decode or execute (or to the CPU currently processing it).

Do not accept responses that state registers are in main memory or that registers store data/instructions permanently.

Do not accept 'registers are a type of memory' or 'registers store the program' as they do not describe a role in the fetch-decode-execute cycle.