Learn: Structure and Function of the Processor

Welcome!Today, we're diving into the Structure and Function of the Processor. This is an important topic in the OCR H446 Computer Science Specification that helps you understand how computers process instructions. Let's explore how processors work step by step!

What is a Processor?A processor, or CPU (Central Processing Unit), is the 'brain' of a computer. It handles all instructions received from software and performs calculations required to complete tasks. Without a processor, a computer wouldn't be able to function.

Key Components of a ProcessorThe CPU is made up of several main parts:Arithmetic Logic Unit (ALU): Performs arithmetic (e.g., addition) and logical operations (e.g., AND, OR).Control Unit (CU): Directs operations inside the CPU, coordinating tasks and managing instructions.Registers: Small, fast storage areas inside the CPU used for temporary data storage during processing.Buses: Pathways that transfer data, addresses, and control signals between components.

Registers in the ProcessorRegisters are very small storage units located inside the CPU. They hold temporary data while instructions are being executed. Key registers include:Program Counter (PC): Stores the address of the next instruction to be executed.Memory Address Register (MAR): Holds the memory location of data that needs to be accessed.Memory Data Register (MDR): Stores the actual data being transferred to/from memory.Current Instruction Register (CIR): Holds the current instruction being executed.

Fetch–Decode–Execute CycleThe Fetch–Decode–Execute cycle is the process by which the CPU carries out instructions. It is the fundamental operation of the CPU and includes three main steps:Fetch: The CPU retrieves the next instruction from memory using the Program Counter (PC) and stores it in the Current Instruction Register (CIR).Decode: The Control Unit interprets the instruction and prepares other parts of the CPU to execute it.Execute: The ALU or other components perform the operation, such as calculations or data transfer.

CPU Performance FactorsSeveral factors affect how quickly a CPU can process instructions:Clock Speed: Measured in GHz, it determines the number of cycles a CPU can complete per second.Number of Cores: More cores allow the CPU to perform multiple tasks simultaneously.Cache Size: Larger cache allows faster access to frequently used data.Pipelining: A technique where different stages of the Fetch–Decode–Execute cycle overlap, improving efficiency.

Review Time!Great work! You've learned about the structure and function of processors, including their components, the Fetch–Decode–Execute cycle, and performance factors. Now let's test your understanding with a few questions.