Introduction to Computer Organization and Architecture

M.Chinyuku What is a Computer? A computer is an electronic device that stores, accepts data, retrieves data, processes data and gives output according to a set of instructions. 2

Elements of a computer  Hardware  Physical components  Software  Computer instructions  User  Human operator M.Chinyuku

Main Hardware Components M.Chinyuku Input Device CPU Output Device Backing Store

Hardware This is the equipment that make up a computer system (physical components). Many of these parts are contained within the computer’s case. Other parts are connected to the computer (peripheral devices). These allow data to be entered (input) and retrieved (output) and stored M.Chinyuku

Input devices (mouse and keyboard) let the user enter data Processing devices (processor) Output devices (monitor, speakers and printer) display data Storage devices (memory sticks and disks) hold data 6 Computer Hardware components

Central Processing Unit The part of the computer performs the bulk of data processing operations is called the central processing unit “Brain” as well as “heart” of computer system The chip or chips at the heart of a computer that enable it to process data. M.Chinyuku

CPU Components The CPU is made up of four major parts: – Register set – ALU – Control units – Main memory Memory: An area within a computer system that holds data waiting to be processed. M.Chinyuku

Components of the CPU Control unit – Control unit: supervises the transfer of information among the registers and instructs the ALU as to which operation to perform by generating control signals. Arithmetic logic unit (ALU) – Performs computation and comparison operations Set of registers – Storage locations that hold inputs and outputs for the ALU – Stores intermediate data during the execution of instructions; M.Chinyuku

CPU Registers Primary functions – Hold data for currently executing program that is needed quickly or frequently (general-purpose registers) – Store information about currently executing program and about status of CPU (special-purpose registers) M.Chinyuku

Input Devices Input is any data entered into the computer’s memory. input devices : the devices that allow data and instructions to enter a computer (such as a keyboard, mouse, scanner) M.Chinyuku

Input Devices Types of input include: – Data – Unorganized information (words, numbers, images, or sounds) that the computer converts to meaningful information – Software – Programs transferred from storage devices to the computer’s memory – Commands – Instructions that tell the computer what to do – Responses – Prompts requiring user feedback M.Chinyuku

Definitions Input device is any device that is used to transfer data into a computer so that it may be processed or stored permanently. Each type of input device has an INTERFACE i.e a means of communication between the human user and the electronic computer M.Chinyuku

Modern data capture Methods Data may be keyed in from source documents by keyboard operators Computer Keyboard Numeric keypad M.Chinyuku

Modern data capture Methods c.t.d. The source documents may be read directly by a document reader. Document readers capture information in the form of pictures or text already printed on paper. Image Scanners Optical Character reader (OCR) Optical Mark reader (OMR) Magnetic ink character reader (MICR) Bar code readers M.Chinyuku

Modern data capture Methods ctd Data may be captured directly without the need for any source document Magnetic strip on a plastic card, Smart card M.Chinyuku

Modern data capture Methods ctd Graphic input devices may be used to translate drawings or photographs into digital form that can be processed by a computer Mouse Track ball Touch screen Digitizing tablet Light pen M.Chinyuku

Sound Input A microphone can be attached to a sound card to provide audio input and also to issue commands and crate files Speech recognition is a type of input in which the computer recognizes words spoken into a microphone. M.Chinyuku

Output Devices Output devices are peripheral devices that enable us to view or hear the computer’s processed data. E.g. a display screen or printer) Output: The product of the transformation of inputs by a process. M.Chinyuku

Output Devices Types of output – Visual output – Text, graphics, and video – Audio output – Sounds, music, and synthesized speech M.Chinyuku

Monitors A monitor is a peripheral device which displays computer output on a screen. Screen output is referred to as soft copy. Types of monitors: – Cathode-ray tube (CRT) – Liquid Crystal Display (LCD or flat-panel) M.Chinyuku

Printers A printer is a peripheral device that produces a physical copy or hard copy of the computer’s output. M.Chinyuku

Types of Printers Laser printer works like a copier Quality determined by dots per inch (dpi) produced Color printers available Expensive initial costs but cheaper to operate per page M.Chinyuku Laser

Types of Printers ctd Inkjet printer, also called a bubble-jet, makes characters by inserting dots of ink onto paper Letter-quality printouts Cost of printer is inexpensive but ink is costly M.Chinyuku Inkjet

Plotter A plotter is a printer that uses a pen that moves over a large revolving sheet of paper. It is used in engineering, drafting, map making, and seismology. M.Chinyuku

Audio Output: Sound Cards and Speakers Audio output is the ability of the computer to output sound. Two components are needed: – Sound card – Plays contents of digitized recordings – Speakers – Attach to sound card M.Chinyuku

Computer Sorage Storage device: – The place where a computer puts data. – The area within a computer system where data can be left on a longer term basis while it is not needed for processing. M.Chinyuku

Why Is Storage Necessary? Storage devices: – Retain data when the computer is turned off – Are cheaper than memory – Play an important role during startup – Are needed for output M.Chinyuku

Storage Technologies: Magnetic and Optical Magnetic – Storage devices use disks or tapes that are coated with magnetically sensitive material Magnetic Optical – Storage devices that use laser beams to read patterns etched into plastic disks Optical M.Chinyuku Magnetic Storage Optical Storage – CD/DVD drive

CD-ROM Discs and Drives CD-ROM stands for Compact Disc- Read Only Memory. CD-ROM drives can not write data to discs. They are capable of storing 650 MB of data. They are used for storing operating systems, large application programs, and multimedia programs. M.Chinyuku

CD-R and CD-RW Discs and Recorders CD-R Discs can be read and written to Discs can only be written to “once” CD-R drives are capable of reading and writing data M.Chinyuku

CD-R and CD-RW Discs and Recorders CD-RW Discs can be read and written to Discs are erasable Discs can be written to many times CD-RW drives are capable of reading, writing, and erasing data M.Chinyuku

DVD-ROM Discs and Drives DVD stands for Digital Video Disc. DVD technology is similar to CD-ROM technology. DVDs are capable of storing up to 17GB of data. The data transfer rate of DVD drives is comparable to that of hard disk drives. DVD-R and DVD-RW drives have the ability to read/write data. M.Chinyuku

Solid State Storage Devices Solid state storage devices use nonvolatile memory chips to retain data. They do not have moving parts. They are small, lightweight, reliable, and portable. M.Chinyuku

Solid State Storage Devices M.Chinyuku Flash Memory Smart Card PC Card

Solid State Storage Devices M.Chinyuku Compact Flash Memory Micro Drive Memory Stick