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Computer Generations The computer passed through develop stages these stages or generation are:
Computer Generations First Generation (Vacuum Tubes) - They relied on the machine language to perform operations. - They were huge in size. - They were very expensive. - They had very low processing speed.
Computer Generations Second Generation (Transistors) - It is smaller. It is faster. It is cheaper.
Computer Generations Third Generation (Integrated Circuits) - The speed and the efficiency of the computers were increased.
Computer Generations Fourth Generation (Present Microprocessor) - The most powerful. - Can be linked together to form networks. - They are the fastest and the most efficient.
Definitions Computer: A computer is an electronic machine that receives input, stores and automatically processes data, and provides output in a useful format. Information Technology: A term that refers to both the hardware and software that is used to store, retrieve and manipulate information.
Definitions Data: Data is raw & unorganized facts and figures that need to be processed. Information: When data is processed and organized to make it useful and meaningful, it is called Information. .
Advantages of computers l Speed and accuracy of calculations and processing. l Save huge amounts of data. l Economic in cost and time. l Network communications.
Types of computer
Super computer l The biggest and the most powerful. l They are rare because of their cost and size. l Used by companies like NASA.
Mainframe computer l Great processing speed and data storage. l Often connected to many individual PCs with limited processing capabilities called dumb terminals. l Used in Banks, Airlines etc.
Minicomputer • Minimized in size and power. • They are not used very commonly these days.
Microcomputer • Called Personal computer (PC) • It is small enough to fit on top of a desk, which can be used by one user at a time. • Used in homes, schools etc. .
Workstation Computer l High-end microcomputer. l Used by one person at a time. l They are commonly connected to a local area network l The workstation term can be also used to refer to a PC connected to a network.
Control computer l Used for controlling operations in industrial, medical devices and travel media like planes and cars l Also used to alert in any dangerous case.
Parts of Personal computers
Computer Hardware Software
Definitions Hardware: The physical parts of a computer which you can see and touch.
Hardware 1) Input Devices 2) Output Devices 3) Processing Unit 4) Memory Unit 5) Storage Devices
Hardware l 1) Input Devices
1) Input devices Devices used to translate the data into a form that the computer can process.
a) Keyboard It is a board containing the keys of letters, numbers and some functions which allows you to type information into the computer.
b) Mouse A small hand-held device used to point, select, click on items and to drag and drop items from one place to another.
C) Scanner It allows you to scan pictures, text and images and save it to your computer in a digital form.
d) Bar Code Reader Photoelectric scanners that translate the bar code symbols into digital form.
E) Joystick l Small hand-lever that can be moved in any directions to control movement on the screen. l It can be used for playing games.
Hardware l 2) Output Devices
2) Output devices Devices used to translate the processed information into a form that humans can understand.
a) Monitor (computer screen) l It displays the text, information and pictures. l They are different in (Size and Resolution)
b) Printer It produces a hard copy of the material you are working on. Types: 1) Laser Printer 2) Ink-jet Printers
C) Plotters It is similar to a printer but allows you to print larger images.
D) Speakers / Headphone They are used to output voice from a computer
Note: Some devices can be used as both Input and output devices at the same time such as: Touch Screen: It receives input from the touch of a finger.
Hardware l 3) Processing unit
CPU ( Central Processing Unit ) l The most important part of a computer system. l Usually referred to as the brain of the computer. l It determines the speed of your computer which measured in MHz or GHz. 1 GHz= 1000 MHz
CPU ( Central Processing Unit ) CPU consists of: l CU (Control Unit): It tells the computer system how to carry out program instructions from the memory. It controls and coordinates all activities of the computer. l ALU (Arithmetic and Logic Unit): It performs mathematical and logical operations
Hardware 4) Memory unit
a) RAM (Random Access Memory) l The operating system is loaded into the RAM when you switch on your computer. l Used to store applications that you are currently working with. l It is temporary (volatile).
b) ROM (read only memory) l It has special programs which are built-in when you buy the computer. l Used to store control programs. l It is permanent (non-volatile)
Hardware l 5) storage Devices
Storage Devices Hardware devices which are used to record and store data.
1) Internal storage Hard disk: l It is the most important storage media in the computer. l It stores operating system and programs.
2) External Storage a) Flash Memory A compact and easy-to-use device for transferring data between computers.
b) CD (Compact Disk) l An optical disk which uses laser to read information. l It has 750 MB capacity.
c) DVD (Digital Versatile Disk) l A high-density video disc that stores large amounts of data, especially high-resolution audiovisual material like movies, encyclopedia etc. l The capacity is up to 17 GB.
Disk and memory capacity The first level of storage is called bit ( the bit is referred to a binary number 0 or 1). Byte = 8 bits. Kilo Byte (KB) = 1024 bytes. Mega Byte (MB) = 1024 KB. Giga Byte (GB) = 1024 MB. Tera Byte (TB) = 1024 GB.
Computer Performance 1. The speed of the processor. 2. The capacity of RAM. 3. The capacity and the speed of the Hard disk. 49