1 ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers

2 Reference Peter Norton, Introduction to Computers, McGraw Hill, 5 th Ed, 2003 ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers

3 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 !!!” ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers

4 Components of a computer system ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers

5 Hardware ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers

6 Hardware CPU: Central Processing Unit – 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

7 Hardware Input and Output devices – 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 … ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers

8 Hardware Memory – Internal memory / Main memory Random Access memory (RAM) – 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 ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers

9 ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers Another kind of memory Read 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)

10 Hardware Storage devices – External memory 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 ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers

11 Hardware Main differences between storage & memory: – 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 ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers

12 ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers Stored Program Concept – In 1949, Dr John Von Neumann defined the stored program concept that greatly affected the development of nowadays computers – Suggested that program instructions should be stored in a memory unit just like data  Instructions: Commands of user  Data: Information that commands work on – Hence rather than hardware programmable, should be software programmable

13 ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers 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)

14 Application Software Develop to fulfill certain needs of users Either customized or packaged – Customized software Designed for a particular customer according to their needs Payroll, inventory control, … – Packaged software Developed for general use Microsoft word, excel, Access, power-point, … ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers

15 System Software 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) ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers

16 Operating System Master control program – Manage all resources of the computer CPU, memory, disk, monitor, network, … – Co-ordinate running programs Runs as soon as the computer boots up, until the computer shuts down Usually store in the hard disk and load into the memory when the computer starts Need the help of BIOS for I/O devices E.g. Windows, Unix, Linux ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers BIOS Operating System I/O Devices Other resources

17 When power up, nothing is in RAM. No control is 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 the operating system to the RAM ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers How the OS is loaded into memory?

18 CPU Main Memory (RAM) BIOS (Stored in ROM) Hard Disk Mother Board Disk Interface Video Interface Monitor Disk Interface Video Interface Bootstrap loader OS ENG224 INFORMATION TECHNOLOGY – Part I 1. Introduction to Computers