The components of a computer(Part I)

Overview : A computer

accepts data and processes it into useful information consists of

input: accepts data in machine-readable form and sends it to the processor.

Processor (CPU):executes computer instructions to turn the data into useful information.

Output:makes the machine-readable information available for users.

Storage:supplements main memory - diskettes, hard disk, CD-ROM, etc.

Main Components of a Computer

Secondary

Storage

Input Processing Output

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

they have larger capacity they retain their contents even when the computer is turned off 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

MICROPROCESSORMICROPROCESSOR

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

MICROPROCESSORMICROPROCESSOR

Microprocessor Comparison Intel processors

• Xeon

• Pentium II with MMX

• Celeron

MICROPROCESSORMICROPROCESSOR

Processor Installation and Upgrades Zero-insertion force (ZIF) sockets Upgrades

• Chip for chip

• Piggyback

• Daughterboard

MICROPROCESSORMICROPROCESSOR

Coprocessors Special processor chip or circuit board designed

to assist the processor in performing specific tasks

Floating-point coprocessor

MICROPROCESSORMICROPROCESSOR

Parallel Processing Using multiple processors simultaneously to

execute a program Speeds execution 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 networkBy far the most important network service is

electronic mailNow the Internet is rapidly gaining in importance