Kartlar: 3 - Computer Systems (Leaving Cert)

Computer system

Combination of hardware (physical parts of the computer), software (programs or apps), data, and a user (human).

Computer architecture

How parts of a computer are physically and logically connected.

von Neumann architecture

A computer architecture designed by a computer scientist in 1945. It consists of four main components: a central processing unit (CPU), memory, a bus, and input/output devices.

Central Processing Unit (CPU)

Carries out computations on data by following instructions, resulting in an output. It contains the control unit, the arithmetic/logic unit (ALU), and registers.

ALU

Where arithmetic and logical processing takes place. It receives instructions and data from memory and operates on the data according to the instructions.

Registers

Temporary storage locations (memory) that the CPU can access quickly when carrying out operations on data.

Memory

Where data, instructions (programs), and results are stored. Modern computers use RAM (Random Access Memory) as internal memory for temporary storage of data and instructions being executed by the CPU.

RAM (Random Access Memory)

Volatile memory that holds data and instructions for the currently executing program but loses its contents when the computer loses power.

ROM (Read Only Memory)

Non-volatile memory that retains its contents even when the computer is powered off, and is typically used for storing important system information such as the computer's BIOS.

BIOS

Basic Input Output System, an example of non-volatile memory used to store the start up instructions of a computer.

Fetch-Decode-Execute Cycle

The process in which the CPU repeatedly gets the next instruction from memory, decodes it to reveal an instruction, runs the instruction, and sends the result back to memory if needed. This cycle happens millions of times per second on modern computers.

Clock

The timing source that controls the operations of the CPU. It generates a continuous stream of electrical pulses at a stable frequency, which are used to synchronize the operations of different circuits in the computer system.

Main factors which determine the speed of a computer

Clock speed, amount of main memory, number of cores, and cache size