© ncc education limited v1.0 introduction to computing unit 1: introduction to computer systems
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Introduction to Computing
Unit 1: Introduction to Computer Systems
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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
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A Computer
• Electronic machine• Processes data• Programmable (follows stored
instructions)• Usually multi-purpose (but not all are)
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Hardware
Physical devices you can see and touch
Examples:• Screens• Keyboards• Printers
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Hardware
• Physical components- such as memory, network cards, wires
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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
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Data
• We use computers to process data.• Data = facts• Data comes in many sorts
- text- numbers- images- music
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Data
To a computer, all data is the same
00010100101010111101010101010
- a collection of bits
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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
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A system
• A collection of parts• Acting together• For some defined purpose
• A system has a boundary
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A System
System OutputInput
processing
sub
systemsystem
boundary
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Examples of Systems
• Digestive system• Banking system• Transport system
What are the parts making up these systems?
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Computer Systems
• The hardware, software and data needed to solve a real-world problem
• The components depend on the problem being solved
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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
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Introduction to Computer Systems Unit 1 - 1.15
Hardware
Hardware is often classified into:
• Input devices
• Output devices
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Hardware
But there are other ways of looking at it:
• Communications
• Storage
• Processing
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Hardware
Processor Output device
Inputdevice
Inputdevice
Inputdevice
Output device
Output device
InputPeripherals
OutputPeripherals
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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
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Analogue and Digital Data
Analogue datacontinuously
variable
Digital dataonly two states
0 or 1
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Input Devices
Common PC input devices:• keyboard• mouse• webcam• microphone• scanner
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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
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Output Devices
These are often needed to convert digital data to analogue information.
They are aimed at human senses or other devices.
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Introduction to Computer Systems Unit 1 - 1.23
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
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Introduction to Computer Systems Unit 1 - 1.24
Output Devices
More examples:• plotters• motors• heaters• lights• actuators• switches
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Introduction to Computer Systems Unit 1 - 1.25
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
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Introduction to Computer Systems Unit 1 - 1.26
Secondary Storage
Magnetic is still important• hard disks, even tapes
Optical• cd• dvd• blu ray
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Introduction to Computer Systems Unit 1 - 1.27
Secondary Storage
Solid state• likely to become more important
- sub notebook PCs- flash memory- camera cards- SIM cards- USB memory sticks
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Introduction to Computer Systems Unit 1 - 1.28
Software
• The instructions that a computer follows
• Produced as a program• Stored on secondary storage• Copied into RAM for running
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Introduction to Computer Systems Unit 1 - 1.29
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:
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Introduction to Computer Systems Unit 1 - 1.30
System Software
• Operating systems• Translation software• Database management systems• Utilities
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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
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System Software
Types:• Single job stream• Multiprogramming• Real-time• Network
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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
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Introduction to Computer Systems Unit 1 - 1.34
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
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Introduction to Computer Systems Unit 1 - 1.35
System Software
Multiprogramming
notice that the processor is active all the time
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Introduction to Computer Systems Unit 1 - 1.36
System Software
Real-time• Output is given immediately after
input- Needed for bookings- Games- Control- Safety-critical systems
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Introduction to Computer Systems Unit 1 - 1.37
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
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Introduction to Computer Systems Unit 1 - 1.38
Network Operating Systems Allow connected computers to:
• Communicate• Share resources• Divide work
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Introduction to Computer Systems Unit 1 - 1.39
Network Operating Systems
• Allow logins• Identify users• Provide security• Log activity
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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
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Introduction to Computer Systems Unit 1 - 1.41
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
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Introduction to Computer Systems Unit 1 - 1.42
Database Management Systems
• Provide a way of separating data form applications
• Allow applications to be created that do not conflict with each other
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Introduction to Computer Systems Unit 1 - 1.43
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
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Different Types of Computer Systems
•Personal Computer•Desktop•Laptop•PDA•Notebook•Sub-notebook
•Workstation•Server•Mainframe•Minicomputer•Supercomputer•Embedded Devices
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The Most Common Computer in the World?
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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
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Data and Information
This is data:• 231189 (the numbers could mean
anything)
This is information:• 23/11/89 (now it looks like a date)
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Introduction to Computer Systems Unit 1 - 1.48
How Computers Developed
The Babbage Difference Engine (designs started 1822)
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Introduction to Computer Systems Unit 1 - 1.49
ColossusThe First Electronic Computer
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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
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Introduction to Computer Systems Unit 1 - 1.51
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
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Third Generation
Integrated circuits• More size and cost reductions• Faster
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Introduction to Computer Systems Unit 1 - 1.53
Fourth Generation
Millions of transistors packed onto a chip• More size reduction• More speed gains
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Introduction to Computer Systems Unit 1 - 1.54
Giving Instructions
patched wires
paper tape
punched cards
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Introduction to Computer Systems Unit 1 - 1.55
Giving Instructions
Console and tape storage - 1970
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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 ); }
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Introduction to Computer Systems Unit 1 - 1.57
Giving Instructions
Command line
GUI
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Nowadays….
Standards have allowed rapid progress:• Proprietary
- Microsoft• Windows• Office
• Open source• Linux• Apache
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Introduction to Computer Systems Unit 1 - 1.59
Unit 1
Any questions?
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