2Lesson Aims By the end of this lesson: Pupils at will be able to: Label a computer system in terms of a 5 block diagramDescribe the phrase ‘word length’Describe the purpose of a processorList and describe the parts of a processor:Control Unit, ALU, registersDescribe what a bus is and does
3A Basic Computer System Nat 4/5A Basic Computer SystemBacking StorageOutputDevicesInput DevicesProcessorMemoryThis is known as the 5 block diagram.
4The 5 Block Diagram Input Devices Output Devices Memory Nat 4/5The 5 Block DiagramInput DevicesThese are devices that enter data INTO the computer. i.e. Keyboard and mouseOutput DevicesThese are devices that generate output FROM the computer i.e. printer.MemoryThere are two types of memory. RAM and ROM (more on this later)Backing StorageThis is required to store permanent copies of our files.
5Arithmetic and Logic Unit (ALU) Nat 4/5The ProcessorThe 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:ProcessorControl UnitArithmetic and Logic Unit (ALU)Registers
6Processor Parts Control Unit Arithmetic and Logic Unit (ALU) Registers Nat 4/5Processor PartsControl UnitThis controls the order of execution and the timing of instructionsArithmetic and Logic Unit (ALU)This performs the calculations for the processor. It also carries out the Logical decisions.RegistersThese are temporary stores of information, at best they will store a few bytes of information.
7Nat 4/532 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 computerThis is the largest binary number that the processor can manipulate in one operation.
8What does a bus do? Control Unit RAM Registers Nat 4/5What does a bus do?ProcessorMain MemoryControl UnitData BusRAMALUAddress BusROMRegistersA bus is a collection of wires which can carry data
9Buses Data Bus Address Bus Nat 4/5BusesData BusThe data bus is used to carry data to and from the CPU and Memory.It will hold a binary word.Address BusThis carries the address of the memory location that is being used
10Mnemonic – CAR(s) Summary Nat 4/5SummaryThe CPU (Central Processing Unit) is the heart of the computerThe CPU has 3 main partsControl UnitControls the timing and order of executionArithmetic and Logic Unit (ALU)Performs the arithmetical and logical functionsRegistersTemporary stores of informationWord length is the length of the biggest binary number that the processor can process in one operationMnemonic – CAR(s)