Topic 4 - Computers
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What is a Hardware Machine?
The physical components that make up a system.
What is a Virtual Machine (VM) ?
A program with the same functionality of a physical computer.
What are the three types of computational models?
Sequential, parallel, multi-agent
What is a sequential computational model?
Algorithms that execute from start to finish, line by line.
What is a parallel computational model?
Algorithms that can be executed simultaneously on multiple processing devices.
What is a multi-agent computational model?
Algorithms that consist of individual agents that work individually and in a decentralised way.
How can we briefly describe a Computer System?
Input –> Process Storage –> Output
What is RAM?
Random Access Memory - anything stored in here can be accessed in roughly the same amount of time.
What is latency?
The time delay between stimulation and response.
What is ROM?
Read-Only Memory: can only be read, not changed or updated, and stores essential programs.
What is a CPU?
Central Processing Unit: the circuitry in a computer and controls the manipulation of data.
What 3 parts does the CPU consist of?
• Arithmetic Logic Unit (ALU) • Registers • Control Unit (CU)
What does the ALU do?
Circuits that perform logical, mathematical operations on data (e.g. + , Boolean)
What do registers do?
Small stores of data within the CPU that temporarily hold data, addresses and instructions.
What does the Control Unit (CU) do?
A circuitry coordinating the activities of a computer.
What does an Address Bus do?
Specifies the physical memory location where the processor needs to read and write to in the memory.
What does a Data Bus do?
Transmits the actual data to and from the memory.
What is the name of the process that the CPU uses when dealing with memory?
Fetch-Execute Cycle
What does the Program Counter (PC) do ?
Stores the memory location of the next instruction to be executed. It increments after the end of the fetch stage.
What does the Current Instruction Register (CIR) do?
Stores instructions currently being processed.
What happens in the FETCH stage (4) ?
• CPU receives address by the PC • Address is added to the address bus. • Main memory receives this and transfers this to a data bus back to CPU. • Instruction stored in the CIR.
What happens in the DECODE stage (2) ?
• CU makes sense of the instruction according to the instruction set. • Instruction decomposed into its individual components.
What happens in the EXECUTE stage?
CU activates and initiates the processing required by the instruction. (i.e. if arithmetic calculation = ALU)
In what form are all computer programs executed in by the processor?
Machine code (1s and 0s)