OCR Computer Science: System Architecture

System Architecture

The Purpose of the CPU

·       The Control Processing Unit is the component of the computer that controls the other devices, executes the instructions and processes the data. It contains the ALU, CU and variety of registers 

Before the cycle starts, the program instructions are copied from a storage device e.g. HDD to the CPU

·       Fetch - In the fetch part of the cycle, instructions and data are moved from the RAM to the CPU

·       Decode - In the decode part of the cycle, the Control Unit (CU) interprets the instructions and decides what actions to perform

·       Execute - These instructions are carried out

Common CPU Components 

Arithmetic Logic Unit (ALU) - allows arithmetic (+, -...) and logic (AND, OR, NOT...) operations to be carried out 

Control Unit (CU) - controls the operation of the computer's ALU, memory and input/output devices, telling them how to respond to the program instructions it has just read and interpreted form the memory unit. The control unit also provides the timing and control signals required by other computer components. The control signals (electrical signals that are sent out to all the devices to check their status and give them instructions) make everything happen…