Computing Science Computer Structure: Lesson 1: Processor Structure Computer Systems Computing Science Computer Structure: Lesson 1: Processor Structure

Lesson Aims By the end of this lesson you will be able to: S3 Computer Systems Processor Structure Lesson Aims By the end of this lesson you will be able to: Label a computer system in terms of a 5 block diagram Describe the phrase ‘word length’ Describe the purpose of a processor List and describe the parts of a processor: Control Unit ALU Registers (Program Counter, Instruction Register) Describe what a bus is and does

A Basic Computer System S3 Computer Systems Processor Structure A Basic Computer System Backing Storage Output Devices Input Devices Processor Memory ROM RAM This is known as the 5 block diagram.

The 5 Block Diagram Input Devices Output Devices Memory S3 Computer Systems Processor Structure The 5 Block Diagram Input Devices These are devices that enter data INTO the computer. i.e. Keyboard and mouse Output Devices These are devices that generate output FROM the computer i.e. printer. Memory There are two types of memory. RAM and ROM (more on this later) Backing Storage This is required to store permanent copies of our files.

Arithmetic and Logic Unit (ALU) S3 Computer Systems Processor Structure The Processor The processor is the ‘brain’ of the computer. It is the piece of equipment that actually performs the instructions required. It can be shown in the following diagram: Processor Control Unit Arithmetic and Logic Unit (ALU) Registers

Processor Parts Control Unit Arithmetic and Logic Unit (ALU) Registers S3 Computer Systems Processor Structure Processor Parts Control Unit This controls the order of execution and the timing of instructions Arithmetic and Logic Unit (ALU) This performs the calculations for the processor. It also carries out the Logical decisions. Registers These are temporary stores of information, at best they will store a few bytes of information.

S3 Computer Systems Processor Structure 32 bit and 64 bit computing? You often hear a processor being described as 32 bit or 64 bit. This is usually referring to the ‘word length’ of the computer This is the largest binary number that the processor can manipulate in one operation.

What does a bus do? Control Unit RAM Registers S3 Computer Systems Processor Structure What does a bus do? Processor – Central Processing Unit Main Memory Data Bus Control Unit RAM ALU Address Bus ROM Registers A bus is a collection of wires which can carry data

Buses Data Bus Address Bus S3 Computer Systems Processor Structure Buses Data Bus The data bus is used to carry data to and from the CPU and Memory. It will hold a binary word. Address Bus This carries the address of the memory location that is being used

Mnemonic – CAR(s) Summary S3 Computer Systems Processor Structure Summary The CPU (Central Processing Unit) is the heart of the computer The CPU has 3 main parts Control Unit Controls the timing and order of execution Arithmetic and Logic Unit (ALU) Performs the arithmetical and logical functions Registers Temporary stores of information Word length is the length of the biggest binary number that the processor can process in one operation Mnemonic – CAR(s)