© ncc education limited v1.0 introduction to computing unit 1: introduction to computer systems

© NCC Education LimitedV1.0

Introduction to Computing

Unit 1: Introduction to Computer Systems


Introduction to Computer Systems Unit 1 - 1.2

Summary of the Lecture

• Some definitions• The parts of a computer system• Examples of computer systems• Data and information• Developments past and present



A Computer

• Electronic machine• Processes data• Programmable (follows stored

instructions)• Usually multi-purpose (but not all are)



Hardware

Physical devices you can see and touch

Examples:• Screens• Keyboards• Printers



Hardware

• Physical components- such as memory, network cards, wires



Software

Software = Computer Instructions• A set of instructions that the computer

carries out• Usually these are carried out one after

another• The software is stored in primary

memory when it is run



Data

• We use computers to process data.• Data = facts• Data comes in many sorts

- text- numbers- images- music



Data

To a computer, all data is the same

00010100101010111101010101010

- a collection of bits



Bits• A bit is the smallest unit of data

• It can be only one of two things:- 0 or 1

• Bits can easily be represented in a computer by switches or transistors

• They are either on or off• A collection of bits can represent any data



A system

• A collection of parts• Acting together• For some defined purpose

• A system has a boundary



A System

System OutputInput

processing

sub

systemsystem

boundary



Examples of Systems

• Digestive system• Banking system• Transport system

What are the parts making up these systems?



Computer Systems

• The hardware, software and data needed to solve a real-world problem

• The components depend on the problem being solved



Hardware

Hardware is any part of a computer system that you can see and touch.

keyboard RAM router

processor printer sensor

cables network card loudspeaker

ports hub motor



Hardware

Hardware is often classified into:

• Input devices

• Output devices



Hardware

But there are other ways of looking at it:

• Communications

• Storage

• Processing



Hardware

Processor Output device

Inputdevice

Inputdevice

Inputdevice

Output device

Output device

InputPeripherals

OutputPeripherals



Input Devices

• Computers can only work with digital data – 0 or 1

• Much of the world is analogue

• Most input devices change analogue data into digital data



Analogue and Digital Data

Analogue datacontinuously

variable

Digital dataonly two states

0 or 1



Input Devices

Common PC input devices:• keyboard• mouse• webcam• microphone• scanner



Input Devices

More examples:• supermarket checkout scanner• temperature sensor• pressure pad in a burglar alarm system• pressure sensor in an aircraft altimeter• OMR reader• RFID reader



Output Devices

These are often needed to convert digital data to analogue information.

They are aimed at human senses or other devices.



Output Devices

Common PC output devicesprinter (ink jet / laser)

screen (some CRT but most now are TFT liquid crystal devices)

these use dots or pixels to produce imagesthe more dots, the better the resolution

speakers

visible

audible



Output Devices

More examples:• plotters• motors• heaters• lights• actuators• switches



Storage Devices

• Data usually needs to be kept for the future

• RAM is volatile and limited• Secondary storage for permanence• Secondary storage is getting faster

and cheaper all the time



Secondary Storage

Magnetic is still important• hard disks, even tapes

Optical• cd• dvd• blu ray



Secondary Storage

Solid state• likely to become more important

- sub notebook PCs- flash memory- camera cards- SIM cards- USB memory sticks



Software

• The instructions that a computer follows

• Produced as a program• Stored on secondary storage• Copied into RAM for running



Software

System software•controls the hardware•makes the hardware

usable- by humans- and other software

Application software

•does the jobs that we want

•solves real-world problems

Can be divided into two main groups:



System Software

• Operating systems• Translation software• Database management systems• Utilities



System Software

Operating systems• Examples: Windows, Unix, Linux, Mac OS• Hide the complexities of the machine• Manage memory• Provide a user interface• Manage peripherals• Manage files



System Software

Types:• Single job stream• Multiprogramming• Real-time• Network



System Software

Single job stream• Early computers processed jobs on

after another• The operating system had to load and

run each job• The CPU was idle when awaiting input

or output



System Software

Multiprogramming• More than one program in RAM at the

same time• Each process is allocated a time slice• CPU switches its attention between

programs• The CPU is used more of the time



System Software

Multiprogramming

notice that the processor is active all the time



System Software

Real-time• Output is given immediately after

input- Needed for bookings- Games- Control- Safety-critical systems



Virtual Memory

• A program can be divided into segments

• Segment loaded into RAM by OS when needed

• Unused segments stay on secondary storage

• Reduces amount of RAM required• Allows bigger programs to be written



Network Operating Systems Allow connected computers to:

• Communicate• Share resources• Divide work



Network Operating Systems

• Allow logins• Identify users• Provide security• Log activity



Translation Software

The CPU only executes machine code:

• Most programs are written in a human readable form (source code)

• The source code has to be translated into machine code



Translation Software

Assembler• works on low level source code – produces a

runnable program file

Compiler• works on high level source code – produces a

runnable program file

Interpreter• works on high level code and executes it as

it goes – no new file produced



Database Management Systems

• Provide a way of separating data form applications

• Allow applications to be created that do not conflict with each other



Utilities

• Operating systems provide a host of utilities

• These are small programs designed to do a limited range of tasks

• E.g. formatter, defragmenter, text editor, compression software



Different Types of Computer Systems

•Personal Computer•Desktop•Laptop•PDA•Notebook•Sub-notebook

•Workstation•Server•Mainframe•Minicomputer•Supercomputer•Embedded Devices



The Most Common Computer in the World?



Data and Information

Data is just facts / symbols:• Computers work with data• They manipulate groups of binary digits• They do exactly what we tell them

Information is facts in context:• We need information• Computers output information



Data and Information

This is data:• 231189 (the numbers could mean

anything)

This is information:• 23/11/89 (now it looks like a date)



How Computers Developed

The Babbage Difference Engine (designs started 1822)



ColossusThe First Electronic Computer



The First Generation

Colossus • The first electronic, programmable,

digital computing device• Used 2400 electronic valves• Designed by Tommy Flowers• Used to decode wartime code

messages



Second generation

Transistors Replace Valves:•Faster•Use less energy•More reliable•Cheaper•Smaller

http://upload.wikimedia.org/wikipedia/commons/e/e2/Transistor-die-KSY34.jpg



Third Generation

Integrated circuits• More size and cost reductions• Faster



Fourth Generation

Millions of transistors packed onto a chip• More size reduction• More speed gains



Giving Instructions

patched wires

paper tape

punched cards



Giving Instructions

Console and tape storage - 1970



Giving Instructions

Instructions in hexadecimal

Instructions in assembly language

Instructions in C++ #include <iostream.h>int main(){cout << "Hello World!" << endl;return 0;}

Instructions in SQL if ( $connect ) { // create the database. if ( ! @mysql_query ( "CREATE DATABASE `$database`" ) ) { die ( mysql_error() ); } else { echo “database created."; } } else { trigger_error ( mysql_error(), E_USER_ERROR ); }



Giving Instructions

Command line

GUI



Nowadays….

Standards have allowed rapid progress:• Proprietary

- Microsoft• Windows• Office

• Open source• Linux• Apache



Unit 1

Any questions?

© ncc education limited v1.0 introduction to computing unit 1: introduction to computer systems

Documents