IGCSE Computer Science Paper 1 Word Scramble: 3.1 Computer Architecture (Modules 218–227)
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Word scramble
Unscramble the letters and write each key term on the line.
1
GRTSEERI
A very small, very fast storage location inside the CPU (not in RAM) that holds one item of data or one address, such as the PC, MAR, MDR, CIR or ACC.
2
RGMAPRO TEOUCNR (CP)
A register in the CPU that holds the address of the next instruction to be fetched. It increments after each fetch and changes when the program jumps.
3
RMA
Memory Address Register: a CPU register that holds the address of the memory location about to be read from or written to. It holds an address, not data, and sends it along the address bus.
4
DRM
Memory Data Register: a CPU register that temporarily holds the data or instruction just fetched from RAM, or data about to be written to RAM. It holds data, not addresses.
5
IRC
Current Instruction Register: holds the instruction copied from the MDR while the control unit decodes it and the CPU executes it. It stores the instruction itself, not an address.
6
CAAMUTLCUOR (CAC)
A register in the CPU that holds data being worked on and the results of ALU calculations, storing intermediate results before they are saved back to memory or output.
7
UBS
A set of wires that carries data, addresses or control signals between the CPU, RAM and other components. More wires means more bits can be carried at once.
8
ESRDSDA UBS
A one-way bus that carries the address of a memory location from the CPU (sent from the MAR) to RAM. It carries addresses, not data.
9
TDAA SBU
A set of wires that carries data and instructions in both directions between the CPU and RAM. It connects to the MDR.
10
LROOTNC USB
A set of wires that carries control signals, such as read and write, from the control unit to other components so they work together. It carries signals, not data or addresses.
Answer Key
IGCSE Computer Science Paper 1 · Modules 218–227
1GRTSEERI → register — A very small, very fast storage location inside the CPU (not in RAM) that holds one item of data or one address, such as the PC, MAR, MDR, CIR or ACC.
2RGMAPRO TEOUCNR (CP) → Program counter (PC) — A register in the CPU that holds the address of the next instruction to be fetched. It increments after each fetch and changes when the program jumps.
3RMA → MAR — Memory Address Register: a CPU register that holds the address of the memory location about to be read from or written to. It holds an address, not data, and sends it along the address bus.
4DRM → MDR — Memory Data Register: a CPU register that temporarily holds the data or instruction just fetched from RAM, or data about to be written to RAM. It holds data, not addresses.
5IRC → CIR — Current Instruction Register: holds the instruction copied from the MDR while the control unit decodes it and the CPU executes it. It stores the instruction itself, not an address.
6CAAMUTLCUOR (CAC) → Accumulator (ACC) — A register in the CPU that holds data being worked on and the results of ALU calculations, storing intermediate results before they are saved back to memory or output.
7UBS → bus — A set of wires that carries data, addresses or control signals between the CPU, RAM and other components. More wires means more bits can be carried at once.
8ESRDSDA UBS → address bus — A one-way bus that carries the address of a memory location from the CPU (sent from the MAR) to RAM. It carries addresses, not data.
9TDAA SBU → data bus — A set of wires that carries data and instructions in both directions between the CPU and RAM. It connects to the MDR.
10LROOTNC USB → control bus — A set of wires that carries control signals, such as read and write, from the control unit to other components so they work together. It carries signals, not data or addresses.