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  • 1. fantaywerku@gmail.com Chapter one Introduction to computer What is computer? A computer is an electronic device capable of manipulating numbers and symbols taking an input, store it, processing it and giving an output, all under the control of a set of instruction called program. Characteristics of a computer A computer is always characterizing by its speed, accuracy and massive storage capacity. Speed: the main feature of a computer is that it perform a lot of instruction with in a second .it speed is measured by millisecond -10-3 second,Microsecond-10-6 second ,Nanosecond -10-9 second and etc. Accuracy: it is accurate to retrieve information and follows a series of instruction that have been perfectly provided in the form of instruction. Reliability: Computer can reliably perform any problem or information given to them by the user as long as the circuitry system is perfectly designed Massive storage capacity: Computer Store large amount of information .you can store large amount of information or data on computer storage device. Types of computer Classification of computer can be based on size, memory capacity and access time or the type of data that the computer processes. Classification according to their Size, Memory and Access time. 1. Microcomputer: is a single user, compact and its memory capacity is also low compare with others. Laptop, portable, desktop 2. Minicomputer: this kind of computer is multi-user .the size of this computer is greater than Microcomputer. 3. Mainframe computer: it is large computer and big institution or organization has this type of computer. 4. Supercomputer: very giant computer and is found only in few institution all over the world like NASA. Super computer process vas amount of information. Computer System Computer system means the composition of computer. Computer system components are classified as hardware and software. The physical equipment that goes together to make up a computer is usually referred to as hardware. Hardware: is the part that you can touch .or the physical make up of the computer. Software: is the set of instruction called a program that directs the computer. fantaywerku@gmail.com 1

2. fantaywerku@gmail.com Computer Hardware Computer hardware is a collection of separate items working together as team. Some of these components are essential: others simply make working more pleasant and efficient. Adding extra item expands the variety of tasks you accomplish with your machine. Your hardware computer system is classified in to two parts: Main or basic components: parts of the hardware that must be present so that the computer performs its basic operator. The system unit The monitor /display unit The keyboard Mouse Optional part: it is the hardware that is optional but their presence makes our work more easier i.e. their absence doesnt affect the basic operation of the computer. Printer Scanner Speaker Modem The main or basic part The system unit: is the central component of your computer. o Mother board: it is large circuit board that holds expansion slot and many different chips .Mother board houses the Microprocessor (CPU), computer memory and other essential chips. Most PC motherboard has slots, which accepts additional circuit board. o Central processing unit (CPU): is also called the heart of the computer or the brain of the computer .The CPU performing two major functions. 1. It Co-ordinate and control the computers activity .for example retrieving files from disk ,interpreting data and commands entered from the keyboard, and sending data to a printer etc 2. It performs arithmetic and logical operations using the binary numbering system (ALU Arithmetic and Logical unit). fantaywerku@gmail.com 2 Computer System Hardware Software Optional part Main Part Application Software Operating System Software 3. fantaywerku@gmail.com o Computer memory: is used to store data or information .Any information inserted from input device is stored in memory. Computer data, that is information, has its own unit .The unit of data or information is Byte(or computer Memory is Expressed in Byte).One byte equal to a single character .The smallest unit of data is Binary Number-Equivalent to a single Zero or one). 1 Bit =1 character 1 Byte=8 Bit 1 Kilo Byte=1KB=1024Byte 1 Mega Byte=1MB 1 Giga Byte =1GB Example Letter A is represented by the binary number 01000001 Computer memory is classified in to two parts RAM (Random Access Memory) -temporary storage device All computer need memory to store data generated by the software .these integrated circuits (RAM) serve as temporary holding tanks for data. Other properties of RAM It is working memory (area) with which CPU interacts for processing. It is power dependent-it store information depends on power i.e. it loses information or its content when the power it off. You can delete, edit as well as read information that is store in it. ROM (Read Only Memory)-Permanent storage device. Contains a small portion of programming .Its memory is permanent. Users or the computer cant change it and its content remains the same even when the power to the computer is removed. The software contained on the ROM is basic input/output system and accommodates expansion hardware. o Storage device Disks: are the most common form of permanent data storage device around magnetize plate usually made up of plastic or metal organized into concentric tracks and pie-shaped sector for storage data. Their are different types of disk Hard disk, floppy disk, CD-ROM disk. o 1.Hard disk : are capable of storing large amount of data .Hard disk drive is much faster than floppy disk drive .It has a higher storage capacity .It can hold from 5MB to 80GB and above .Hard disk perform is measured in terms of access speed and transfer rate. 2. Floppy disk: perform the same basic function as hard disk and work much the same way. The most important difference is that hard disk cannot be inserting removed. It is used for storing relative small amount of information and also for transferring programs and data between one computer and another -5 inch in diameter disk can hold anywhere from 360 to 1.2 MB -3 inch in diameter disk is capable of fantaywerku@gmail.com 3 4. fantaywerku@gmail.com holding up to 2.88 MB of information . o 3.CD-ROM: (compact disk read only memory) disk is a special kind of computer disk that store enormous amount of information ,A CD_ROM has many times the capacity of typical floppy disk yet transfer information at approximately the same speed as floppy disk. Keyboard: is an input device that is used to type or entering information into the computer. Computer Keyboards are divided into five functional areas. 1. Typing Keys: work just like those on a conventional typewriter. 2. Computer Keys: which are not found on the typewriters. They execute special tasks when used alone or in combination with other keys. 3. Functional Keys: perform different tasks depending on the software being used. 4. Dedicated cursor (Arrow Keys): are used to position the cursor on your screen. 5. Numerical Keypad: lets you either move the cursor or input numeric data. The keyboard also has a status indicator area .This area has three lights that display the status (on or off) of Num Lock, Caps Lock. Monitor: It is display unit. Optional part of Hardware Scanner: is a device that enables to transform printer text or image into an electronic text or image. For example you can transfer any printable text or graphs like photos to computer data. Printer: is a device that enables to transform an electronic text or image into printer text or image. Modems and soon. Computer Software What is software? Software enables a computer to operate and perform tasks. Computer programs are considered as software .Programs is detailed step-by-step instruction that tell a computer how to complete a specific task. They are written in programming languages such as Visual Basic, Pascal, and C++ .Without it, computer world is useless much like a camera without a film or a photograph with out records. The software used by computer falls into one of these Two-Category: System Software and Application Software Operating System software: is as vital link between the computer hardware and application software. Without the operating system, application software would be unable to function. The operating system is fantaywerku@gmail.com 4 5. fantaywerku@gmail.com used to name, save, retrieve and maintain the program and data file you create and use on the computer. Chapter Two Case & Power Supply System Unit Cases System units may be packaged in a number of standard case designs. The key characteristics for case design include mounting methods for components, ventilation characteristics, drive capacity, and footprint (desk space they take up). Desktops The most familiar PC case style is probably the desktop case design. These cases are designed to set horizontally on the desk (hence the name). Variations of the basic desktop design include narrow cases, referred to as baby AT cases, and short desktops, called low-profile cases. Towers Tower cases sit vertically on the floor beneath the desk. This case design came about to free up workspace on the desktop. Tower cases offer extended drive bay capacities that make them especially useful in file server applications where many disk, CD-ROM, and tape drive units may be desired. Although tower designs are convenient, their ventilation characteristics tend to be poor. Adapter cards are mounted horizontally in tower units and the heat produced by the lower cards must rise past the upper cards, adding to their heat build up. To compensate for this problem, most tower cases include a secondary fan unit to increase airflow through the case and thereby dissipate more heat. Mini towers and mid towers are short towers designed to take up less vertical space. Full towers are common in server machines.