The components of a computer (Part I)

Overview : A computer § accepts data and processes it into useful information §consists of l input: accepts data in machine-readable form and sends it to the processor. l Processor (CPU):executes computer instructions to turn the data into useful information. l Output:makes the machine-readable information available for users. l Storage:supplements main memory - diskettes, hard disk, CD-ROM, etc.

Main Components of a Computer Secondary Storage InputProcessingOutput

Input §Input devices accept data and instructions from the user §keyboard: you type in your input (the display screen is actually an output device §mouse:moves pointer on screen, pressing button invokes commands §scanners: bar code readers, flat bed scanners, etc., captures codes, photos, drawings, text into the computer directly §writing tablets:reads hand-written Chinese characters §data glove: captures gestures as well as 3D coordinates §sensors:temperature, pressure,… §card readers: one line of data/instruction per card

Processor §The central processing unit (CPU) is the brain of the computer §it transforms raw data into useful information §it executes program instructions §it consists of electronic circuits etched into silicon or other material - a chip of a set of chips plugged into circuit boards

Memory §Computer memory, or primary storage, is not part of the CPU but closely associated with it §memory holds the program and the data being processes by the CPU §while the data and program are in memory, the processor can communicate with it directly §this built-in memory is called random-access memory (RAM) §the common unit of measures is the byte-8 bits - the amount needed to store a single character (Chinese characters need more than 1 byte) §common short-hands - kilobyte (KB) and megabyte (MB)

Output §Raw data processed into useable information §2 common devices are the display screen (monitor) and the printer §early monitors display only characters in one color, now they can display any shape or symbols in virtually any color §printers produce printed material under the control of a program

Secondary Storage §Secondary storage is where the computer stores data and programs that it is not currently using §common media : magnetic disk and magnetic tape §data in secondary storage cannot be accessed directly (unlike main memory) §but l they have larger capacity l they retain their contents even when the computer is turned off l they are much cheaper per unit

§Common diskettes come in 2 sizes: 3-1/2 and 5-1/4 §hard disks have large capacity and offer faster access time then diskettes §optical disks have much higher capacity, but cannot be written on easily §magnetic tape is similar to audio/video tapes, they are inexpensive, but can only be accessed sequentially

MICROPROCESSOR §Microprocessor Comparison l Intel Pentium l Intel Celeron l AMD (Intel-compatible) l Motorola PowerPC l Alpha

MICROPROCESSOR §Microprocessor Comparison l Intel processors Xeon Pentium II with MMX Celeron

MICROPROCESSOR §Processor Installation and Upgrades l Zero-insertion force (ZIF) sockets l Upgrades Chip for chip Piggyback Daughterboard

MICROPROCESSOR §Coprocessors l Special processor chip or circuit board designed to assist the processor in performing specific tasks l Floating-point coprocessor

MICROPROCESSOR §Parallel Processing l Using multiple processors simultaneously to execute a program l Speeds execution l Requires special software

Classes of Computers §Mainframes - very high speeds and very large data volumes §Minicomputers - a step down §Super-minis §Personal Computers(PC) - microcomputers §Super-micros §laptops - notebooks, runs on battery §Sub-notebooks §Pen-based Computers - personal digital assistants

Communication §Computers started out very large, with many dumb terminals connected §Gradually computers become smaller and smaller, with only one set of keyboard/monitor §These PCs need to communicate with one another, as well as mainframes §Again we have many PCs (intelligent terminals) connected to mainframe, or many mainframes

A Simple Computer Network §Processing have been decentralized, or distributed §It becomes a network §By far the most important network service is electronic mail §Now the Internet is rapidly gaining in importance