Computer Hardware General Overview

Hardware: The internal structure of computers, how they operate and how they are used in solving problems.

Programming -is about Software…why do we have to learn about Hardware and other stuff? Because we as computer students will be future doctors of computers and it is very essential to learn all about computers.

What is a Computer System?
What is it comprise of?
How would you define it?

Computer System is composed of two major factors.
1. Hardware
2. Software

Hardware=The physical components (electrical circuits) that make up the computer

Software=The computer programs (sequences of instructions) that tell the computer what to do in response to a command or some event.

Components of a Computer
INPUT DEVICES - For reading data into Main Memory

PROCESSOR - For processing the data

MAIN MEMORY - The program currently being executed is stored here.(it is divided into storage units called BYTES)

AUXILIARY STORAGE - For permanent storage of programs and data

OUTPUT DEVICES - For printing, displaying Or out-put of info


Think of the Brain (System)
1. INPUT - Study for exam
2. PROCESS - Understand and memorize information
3. OUTPUT - Results of the exam

Computer Systems are the same
Data is INPUT
Data is PROCESSED
Something is OUTPUT

*GIGO (Garbage in…Garbage out..)

Types of Computer:
1. Microcomputer
2. Minicomputers
3. Mainframe Computers
4. Supercomputers

Minicomputers:
- Multi-user systems
- 100’s of workstations or terminals attached to central minicomputer
- E.g. EPOS (Electronic Point of Sale) Systems

Mainframe computers
- Large Organisations –banks, building societies, airlines, governments
- May have 1000’s of terminals –geographically remote locations
- Could occupy a whole site
- 100’s of disk drives & hardware units
- Location often kept secret! (terrorist attacks)

Supercomputers
- Largest Category of computer
- Cost Millions
- Mostly used by scientific and industrial research departments
- NASA –government agencies
- Weather Centres
- Stock Exchanges
- Large Commercial Organisations

The processor:
- PROCESSES!
- Faster the processor, better the PC?
Brain of the computer
- Processes instructions
THREE STEPS:
1) Fetches Instructions
2) Decodes Instruction
3) Executes Instruction

CHIP:
A computer chip is an electronic circuit (consisting mainly of semiconductor devices, as well as passive components) that has been manufactured in the surface of a thin substrate of semiconductor material.

An electric circuit is made from different electrical components such as transistors, resistors, capacitors and diodes, that are connected to each other in different ways. These components have different behaviors.

The transistor acts like a switch
Resistor –resists electricity –so you can control current
Capacitor –controls electricity
Diode –also allows control of current and flow

Why Integrated Circuits (transistors)?
- Before –there were VACUUM TUBE
- They were huge
–costly
–bulky
–easily burned out
- The first Computer –ENIAC –huge 30 ton monster! *use of 18000 or so vacuum tubes*

A hybrid integrated circuit is a miniaturized electronic circuit constructed of individual semiconductor devices, as well as passive components, bonded to a substrate or circuit board.

MAIN MEMORY (MM):
- The program currently being executed and the data used by the program is held in MAIN MEMORY
- MM is divided into millions of individually addressable storage units called BYTES
- One byte can hold one character Or one byte can hold a code representing something –i.e a part of a picture, or a sound, or a program instruction.
The total number of bytes in MM = The computers MEMORY SIZE.

Computer Memory Sizes:
1 KB (KB) =1024 Bytes
1 MB =1024KB
1 GB =1024MB
1Tb =1024GB (about 1 trillion bytes)

RAM and ROM:
There are two kinds of Memory:

RAM
–Random Access Memory (MM)
- (this is used for storing programs that are currently running and data that is being processed)
- Main Memory
- Stores info about applications that are open and data
- VOLATILE = When you switch off the machine, it disappears!!!


ROM
–Read Only Memory
- (its contents are PERMANENTLY etched into the memory chip at the manufacturing stage. It is used –for example –to load the bootstrap loader (the program that loads as soon as you start the machine)
- Non-Volatile (does not change)
- Programs that are necessary for the computer to run
- Boot up program
- stores files and programs.

Cache Memory
- This is a very FAST type of memory that is used to improve the spped of a computer, DOUBLING it ….in some cases.
- Acts as an intermediate store between CPU and MM
- It works by storing most frequently or recently used instructions so that it is fast to retrive them again.
- Cache is usually between 1KB and 512KB

Disk Storage:
- Auxiliary storage is also called
- SECONDARY MEMORY
- BACKING STORE
- EXTERNAL MEMORY
- The most common secondary memory (auxiliary storage) is DISK!

Other types of Storage:
- Flash Memory Cards
- Sticks
- Floppy discs
- Disks

INPUT AND OUTPUT devices:
Input devices are the means whereby computers can accept data or instructions

Keyboards, magnetic strip cards, smart cards, magnetic ink character recognition devices,

Output –printer, VDU monitors, speakers, etc

Embedded Computers and special-purpose computers:
Not necessarily all computers are general purpose compuers with a screen, keyboard and disk drive. Special-purpose or dedicated computers can do all sorts of things from controlling the temperature in a greenhouse to controlling traffic lights or using a cash point. Embedded Computers are used in household goods automobiles and in industry