GSCE computer studdies (edexel) - unit 3

memory

Memory is a key internal component of a computer system. It is used by the CPU when running programs and processing data. There are three types of memory: RAM, ROM and cache.

CPU (Central Processing Unit)

The internal operating unit or "brain" of a computer. prossesses program instructions

ROM

Read Only Memory- This is volatile memory or storage containing data that cannot be changed.

RAM

Random Access Memory- This is volatile memory that is constantly being written to and read from. It does not retain its contents without a constant supply of power. When a computer is turned off, everything stored in its RAM is lost.

Secondary Storage

Non volatile memory external to the CPU and used for long-term storage of programs and data.

Volitile Memory

The memory used to store computer program data while it is being executed. RAM is the main type of volatile memory. It is volatile because when power is switched off it no longer retains any data.

program

Sequences of instructions for a computer.

operating system

The software that manages the hardware and software resources in a computer system.

contains hardware

File management

prossess management

proiforal management

user management

non-volatile memory

A form of computer memory that stores data even when not powered

instruction

A single action that can be performed by a computer processor.

Hardware

The physical parts of a computer system, eg a graphics card, hard disk drive or CD drive.

data

Units of information. In computing there can be different data types, including integers, characters and Boolean. Data is often acted on by instructions.

cache memory

A type of memory used to temporarily store frequently used data or programs for quick access; similar to RAM but faster.

Manual input devices

Data is input into the computer by hand.

1. Keyboard

2. Numeric Keypad

3. Pointing Devices

4. Remote Control

5. Joystick

6. Touch Screen

7. Scanner

8. Digital Cameras

9. Microphone

10. Senors

11. Temperature Sensors

12. Pressure Sensor

13. Light sensor

14. Graphics Tablet

15. Video Camera

16. Web Cam

Automatic input devices

· M.I.C.R ( Magnetic Ink Character Recognition)

· O.M.R (Optical mark Recognition)

· O.C.R (optical character recognition)

· Barcode Reader

· Magnetic Stripe Card

· Sensors

Output devices

printer, monitor, speakers, lights - gives user prosessed data

Fetch-Decode-Execute Cycle

The CPU fetches the instructions one at a time from the main memory into the registers. One register is the program counter (pc). The pc holds the memory address of the next instruction to be fetched from main memory.

The CPU decodes the instruction.

The CPU executes the instruction.

Repeat until there are no more instructions.

embedded systems

a combination of computer hardware and software designed for a specific function.

eg: digital watches.

electronic calculators.

GPS systems.

fitness trackers.

Virtual Memory

process of optimizing RAM storage by borrowing hard drive space

Utility Software

systems software that perform tasks related to managing the computer's resources

defragmentation

Back up

anti malware

file repair

data compression

system software

Systems software helps run and maintain the computer. It includes the operating system, drivers and utility software.

It contains:

operating system

utility software

Operating Software

software that operates the computer

Applications software

Applications software is used to carry out tasks on a computer,

what are two main types of software

systems software

applications software

What's a programming language?

a vocabulary and set of grammatical rules for instructing a computer or computing device to perform specific tasks.

Machine Code

Instructions in binary used by the CPU

Assembly Language

Programming language that has the same structure and set of commands as machine languages but allows programmers to use symbolic representations of numeric machine code.

Examples of high level languages

C++, Delphi, Java, Pascal, Python, Visual basic.

Examples of low level languages

Machine code and assembly language

what are translators

A translator is a program that converts source code into machine code.

Storred program concept

Program/ instructions storred in main memory and as each instruction is needed by the cpu they are retrieved by the tech decode execute cycle

Fetch

Program counter - memory address register - main memory

at same time control bus send signal to main memory

main memory - data bus (instruction) - memory buffer register - current instruction register

decode

Control unit understands instruction ( if needs addition value it will use fetch to get that value)

control unit directs the arithmetic logic unit what to do

exicute

Completes instruction

Magnetic secondary storage

Oldest secondary storage (hard disk drive) verry cheep but mechanical not as robust

Solid State Secondary Storage

NAND flash chips (usb)

Optical Secondary Storage

Use lasers need optical drive but portable for example DVD & CD

Actuator

Main out put of an embedded system

Proiforal devices

Input out put devices

keyboard

mouse

Prosses managment

Good access to ram and cpu

file managment

Organises file