Transcript Part I 1. Introduction to Computers

ENG224
INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
1. Introduction to Computers
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ENG224
INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
Reference
Peter Norton, Introduction to Computers,
McGraw Hill, 5th Ed, 2003
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ENG224
INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
ENIAC
• The first practical
computer
• Built in 1945,
weighed more than
30 tons
• Require 1500 sq. feet
In 1949, Popular Mechanics magazine predicted
“computers in the future may perhaps only weigh
1.5 tons !!!”
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INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
Components of a computer
system
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INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
Hardware
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INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
Hardware
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CPU: Central Processing Unit
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Brain of the computer
Manages all devices and performs the actual
processing of data
Carry out instructions given by user
For Personal Computer (PC), the CPU is usually
included in a single Integrated Circuit (IC) chip
(called Microprocessor)
Nowadays, one or more microprocessors (chips)
can be used to form a CPU
 Parallel Processing
ENG224
INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
Hardware
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Input and Output devices
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Interface between the outside world and the
computer system
Input devices: keyboard, mouse
Output devices: monitors, printers
Other I/O devices: network adapter, USB, disk
interface …
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INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
Hardware
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Memory
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Internal memory / Main memory
 Random Access memory (RAM)
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Main feature 1: volatile
 requires continuous supply of electrical power
to retain information
Main feature 2: cheap in terms of bytes per dollar
 suitable for large volume data storage
Functions:
 Receive commands / data from keyboard
 Store info ready to be sent to output
 Store currently running programs/their data
 Store immediate data generated by the currently
running programs
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INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
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Another kind of memory
 Read
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Only Memory (ROM)
Main feature 1: non-volatile
 data retain even when the power is off
Main feature 2: relatively expensive and can only be
written once
 suitable for storing essential data but in small
volume
Usually used for system boot up and basic control of I/O
devices
 When a computer first powers up, nothing is in RAM
 Need ROM to store the instructions to set up
various I/O devices, such as disk interface card,
video adapter card, sound card, etc.
ROM is used to store BIOS (Basic Input/Output Systems)
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INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
Hardware
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Storage devices
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External memory
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Non-volatile
Used to store programs/data for future use
Also used when the capacity of the internal storage is
insufficient to keep the currently running programs
and the data required
Floppy disks, hard disks, CD ROMs, Magnetic tapes
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INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
Hardware
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Main differences between storage & memory:
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Larger capacity in storage than in memory
Data in storage are retained while data in memory
disappear when power is off
Storage is much cheaper than memory
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INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
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Stored Program Concept
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In 1949, Dr John Von Neumann defined the stored
program concept that greatly affected the
development of nowadays computers
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Suggested that program instructions should be
stored in a memory unit just like data
 Instructions: Commands of user
 Data: Information that commands work on
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Hence rather than hardware programmable, should
be software programmable
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INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
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User interacts with application software
System software enables the application software
to interact with computer CPU and help the
computer to manage its internal resources
(hardware)
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INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
Application Software
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Develop to fulfill certain needs of users
Either customized or packaged
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Customized software
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Packaged software
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Designed for a particular customer according to their
needs
Payroll, inventory control, …
Developed for general use
Microsoft word, excel, Access, power-point, …
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INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
System Software
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Exists primarily for the computer itself
Hides the hardware complexities
Brings the different hardware configurations
into common platforms and accessible by the
users
Consists of several programs, the most
important one is the operating system (master
control program that runs the computer)
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INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
Operating System
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Master control program
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Manage all resources of the computer
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CPU, memory, disk, monitor,
network, …
Co-ordinate running programs
Operating
System
Runs as soon as the computer
boots up, until the computer shuts
BIOS
down
Usually store in the hard disk and
load into the memory when the
computer starts
Other I/O Devices
Need the help of BIOS for I/O
resources
devices
E.g. Windows, Unix, Linux
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INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
How the OS is loaded into memory?
• When power up, nothing is in RAM. No control is
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possible to the hard disk to load the OS
CPU starts to read the BIOS instructions stored in the
ROM
Things that normally perform
– Initialize all I/O devices: hard disk, video, mouse,
keyboard, CD-ROM, etc
– Load the bootstrap loader of the operating system
to RAM
– Start to execute the bootstrap loader in RAM
• The bootstrap loader further loads the other part of
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the operating system to the RAM
ENG224
INFORMATION TECHNOLOGY – Part I
1. Introduction to Computers
Hard Disk
Bootstrap
OS loader
Disk
Interface
Monitor
Video
Interface
Main Memory (RAM)
Bootstrap loader
OS
CPU
Mother Board
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BIOS
(Stored in
ROM)