Computer: It is an electronic device that accepts input, stores large quantities of data and executes complex instructions which direct it to perform mathematical and logical operations and outputs the answers in a human readable form. - Computer used rather than human for accuracy and speed. Computer hardware: consists of all the machinery and equipment in a computer system. It is includes: keyboard, mouse, monitor, printer and others. In case box the content of device itself. Computer software: consists of all the instructions that lead computer to perform particular task. Computer system consists of the following units: 1- Input unit. 2- Memory unit. 3- Central unit (CPU). 4- Output unit. 5- Bus unit. Difficulties: The main difficulty in functioning of the units of computer is speed mismatch between the units. CPU speed ---- MIPS. Main memory 10 times slower than CPU speed. I/O units 1000 times slower than CPU speed. One way reduces the speed mismatch problem through buffering. The purpose of a computer is to process data in to information. Data consists of the raw facts and figures that are processed into information. 1
Computer Hardware Software Input Units Case contents Output Units Operating systems Applicatio n )Mouse( (Motherboard( Monitor Graphical based software Text )keyboard( CPU Printer Text based Tables (Microphone) Memory Speakers Presentation Drivers Headphone Data management and analysis Cards Other 2
1- Computer hardware: Mouse: Figure 1: Computer Components A mouse is a small device used to point to and select items on your computers screen. - It is connected to the system unit by a long wire that resembles a tail. - There are wireless mouse. A mouse has two buttons: a primary button (left button) and secondary button (left button). Mouse also has a wheel between the two buttons, which allows to scroll smoothly through screens of information. Keyboard: A keyboard is used mainly for typing text into your computer. Like the keyboard on a typewriter, it has keys for letters and numbers, but it also has special keys. Monitor: A monitor displays information in visual form, using text and graphics. The portion of the monitor that displays the information is called the screen. - There are two types of monitors: 1- CRT (Cathode ray tube). 2- LCD monitors (Liquid crystal display). LCD monitors much thinner and lighter. CRT more affordable. Printer: A printer transfers data from a computer onto paper. Printer allows you to print text on paper, photos and others. 3
Speakers: Speakers are used to play sound. It may build in to system or connected with cables. Speakers allow you to hear sound from your computer. Modem: Modem is used to connect computer to Internet. It sends and receives computer information over a telephone line or high-speed cable. There are two types of modems: a- Built in to the system. b- Separate modems. Separate modems are usually higher-speed than built in to the system modem. Memory: The memory unit is an essential component in any digital computer since it is needed for storing and data. A memory unit is an a collection of storage cells together with associated circuits needed to transfer information in and out of storage. Generally, the memory can be divided in to: Main memory (Primary memory): This is relatively large and fast memory used for program and data storage during computer operation. There are mainly two types of primary storage: 1- RAM (Random Access Memory) It temporary holds software instructions and data before and after by CPU. RAM is said to be volatile because of losing its contents when power is turned off. Two types of RAM used in personal computers: 4
a- DRAM (Dynamic Read/ write memory) Types of DRAM: - DRAM(dynamic RAM) - DDR-SDRAM (Double Data Rate SDRAM): some time called DDR1. - DDR2-SDRAM - DDR3-SDRAM b- SRAM (Static RAM): it is faster than any DRAM. 2- ROM (Read Only Memory): It is used to store fixed startup instructions to which data is constantly being stored. Secondary memory (Auxiliary memory): - It is generally much large in capacity but also much slower than main memory. - It is used to store system and data files. Hard disk drive, CD and DVD are examples of secondary memory. Hard disk drive: Hard disk drive stores information on a hard disk. It can hold massive amounts of information and this made it serve as primary storage. CD and DVD drivers: CD drivers use lasers to read data from a CD, and many CD drivers can also write data on to CDs. Recordable disk drive allows you to store copies of your files on blank CDs. DVD drivers: DVD drivers can do everything that CD drivers can do, and read DVDs. Many of DVD drivers can record data on to blank DVD. 5
Figure 2: Memory hierarchy in computer system CPU (Central Processing Units): It works hand in hand with other circuits known as main memory to carry out. The CPU is the brain of the computer. A typical CPU has three major components: ALU (Arithmetic and Logical unit): carries out the arithmetic and logical operations. - Arithmetic operation like (+,-,*,/) - Logical operation like (>, <, >=, <=,!=, ==) - C.U. (Control Unit): It determines which function to be done on data, decodes instructions, and controls the flow of the program. Register unit: It is high speed memory units used by CPU. Motherboard: Motherboard may have a form factor of AT or ATX. ATX motherboard with ATX cases since this is newer and most modern microprocessors run on ATX motherboards. Motherboard holds the microprocessor, the memory and several card slots. It is mother of all boards in the computer. 6
2-Computer Software: Collection of that installed in system to do specific task and it can be divided in to two types: 1- Operating System (O.S.): O.S. is a program that acts as an intermediary between a user of a computer and the computer hardware. Another definition for the operating system is program that Controls and coordinates use of hardware among various applications and users. Operating system goals: Execute user and make solving user problems easier Make the computer system convenient to use the computer hardware in an efficient manner. - To use any computer it is compulsory O.S. should be installed in this computer. - O.S. can be divided in to two types: a- Graphical based software : It is depended on windows and use mouse as input unit. For example: all types of windows and Linux. b- Text based software: It used keyboard only to enter the commands and doesn t use mouse. For example: DOS (Disk Operating System). 2- Application Programs: This type of software install in system whenever we need for using this. There are different types of application and it is related to type of work that you want to do. Examples of application : - Microsoft office (Microsoft word, Microsoft Excel, Microsoft Power Point). The end of lecture one introduction to computer 7