Common CPU components and their functions

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what are the 4 main components of the CPU?

control unit (CU), arithmetic logic unit (ALU), registers and cache

what are the functions of the control unit (CU)

1. it fetches, decodes and executes instructions

2. it issues control signals that control hardware

3. it moves data around the system

what are two main functions of the arithmetic logic unit (ALU)

1. it performs arithmetic and logical operations. The ALU is where calculations are done and where decisions are made

2. It acts as a gateway between primary memory and secondary storage. Data transferred between them passes through the ALU.

what is a register and what does it do?

A very fast memory location in the CPU and they store data required for an instruction or the result of executing an instruction

what are the four registers in the CPU?

program counter (PC), memory address register (MAR), memory data register (MDR), and accumulator (ACC).

what does the program counter do?

holds the address of the next instruction to be executed. it is incremented by 1 as soon as that instruction is fetched

what does the MAR do?

holds the address of the current instruction, and then the memory address of any data that the instruction uses, so that these can be fetched from memory

what does the MDR do?

holds the actual instruction fetched from memory, and then the data that has been fetched from, or written to memory

what does the accumulator do?

holds the results from the ALU after an instruction is executed before it is transferred to main memory