Computer Hardware - General Overview

Programming  -is about Software…why do we have to learn about Hardware and other stuff?

Computer Systems

Hardware
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.

How do we communicate with computers?
Through the use of binary Language.

Components of a Computer
- Input Devices
- Precessing Devices
- Storage Devices (Primary and Secondary)
- Output Devices.

Computer Processing System:
1. Data is INPUT
2. Data is Processed
3. There is an OUTPUT

IPO - Input, Process, Output.
or commonly known as GIGO - Garbage In, Garbage Out.

Types of Computer
- Microcomputer
- Minicomputers
- Mainframe Computers
- 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 MillionsMostly used by scientific and industrial research departments
NASA –government agenciesWeather Centres
Stock Exchanges
Large Commercial Organisations

The processor
 
 What is the equivalent (in humans) to the processor?
 The Human Brain.

How does the Brain process?
-receives an instruction (stimulus)
-decodes & produces an appropriate instruction
-executes the instruction!
-slap on the cheek –anger/revenge etc logged
-anger decoded –instruction to slap back
-slap back!
(OR TURN THE OTHER CHEEK?)

Processor:
-Brain of the computer
-Processes instructions

THREE STEPS
1) Fetches Instructions
2) Decodes Instruction
3) Executes Instruction

What is a Processor?
-Most computers use integrated chips….or integrated circuits for their processors or main
memory
-A chip is about 1cm square…and can hold MILLIONS of electronic components such as
transistors and resistors
-CPU of a microcomputer is a microprocessor
-Processor and MAIN MEMORY of a PC are held on a single board called a motherboard.
-Either chips or integrated circuits
-Integrated circuits are also found in almost every modern electrical device such as cars, television sets, CD players, cellular phones, etc.


 CHIP
A computer chip is an electronic circuit (consisting mainly ofsemiconductor 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 astransistors, resistors, capacitors and diodes, that are connected to each other in different ways. These components have differentbehaviors.


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*

MAIN MEMORY
-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)
 
 Main Memory
-Processing power and Main Memory in a computer has increased exponentially in the past year! It has grown at a rate that no one could have predicted.
-1980 –Microcomputers with 32K of memory were bought for thousands of homes and schools!

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)

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)

RAM
-Random Access memory
-Main Memory
-Stores info about applications that are open and data
-VOLATILE –
-When you switch off the machine, it disappears!!!

ROM
-Read only memory
-Non-Volatile (does not change)
-Programs that are necessary for the computer to run
-Boot up program
-etc

 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!

Hard disk  & Floppy Disk
All standalone PC’s come equipped with an in-built hard disk –the capacity of which is also measured in BYTES.

A typical hard disk nowadays is several gigabytes - - is used for storing software including the OPERATING SYSTEM..and other systems software.
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

There are two types of software:
-Systems software: the operating system.
-Applications software: the programs we use.
*Systems software is the control software that operates the hardware and allows the applications to run.

OPERATING SYSTEMS
-Operating Systems run in the background without the users being aware of it.
-It controls the inputs, outputs, interrupts, and storage of files as requested by the applications software.
APPLICATIONS SOFTWARE
ÒUsed for a specific purpose or application.
-Word processing;
-Numerical analysis and storage;
-Recording of data;
-Designing and graphics;
-Image processing;
-Presentations;
-Desk top publishing;
-Web design.