Download Computer

INFO 130.20
Martin van Bommel
1999-2000
What is a Computer?
Computer - electronic device that accepts input,
performs calculations, and produces the required
results
 Hardware - components of computer system that
you can see and touch
e.g. keyboard, screen, disk drive, printer, circuit
board
 Software - list of instructions for computer to
perform a specific task
e.g. operating system, word processor, Windows

Input - Processing - Output

Input - what you type, read, or enter into
computer
– Devices - keyboard, mouse, scanner, sensors

Processing - changing the input data via
formatting, sorting, and calculations
– Devices - components on motherboard, CPU, ALU,
memory

Output - results of computer processing
– Devices - screen, printer, plotter, signals

Storage - save information for later processing
– Devices - memory, diskette, hard disk, tape
Types of Computers

Microcomputers or Personal Computers (PCs)
– inexpensive - $500 - $15,000
– small enough to fit on desk
– CPU contained on single chip

Minicomputers and Mainframes
– $15,000 - millions
– too large for desktop
– larger capacity for storing and manipulating data

Servers
– Usually fast microcomputers or small minicomputers
– Lots of memory and disk space
Processing Hardware

Microprocessor or Central Processing Unit (CPU)
– integrated circuit chip on the motherboard
– performs arithmetic and logical operations

Input/Output Interface Cards (I/O Cards)
– provide connection between CPU and I/O devices

Floppy and Hard Disk Drives
– storage external to the motherboard

Memory
– temporary storage on the motherboard
Data Representation
bit - binary digit - 0 or 1
 byte - eight bits
 ASCII code - each character represented by 8 bits

Number
Binary
0
00000000
1
00000001
...
255
11111111
Character
ASCII .
A
01000001
B
01000010
...
Z
01011010
Memory

ROM - Read-Only Memory
– permanent memory installed by manufacturer
– initial instructions for computer on start-up

RAM - Random-Access Memory
– temporary storage for data and instructions
– lost when power off
Byte = 8 bits
 K - Kilobyte - 1024 bytes
 MB - Megabyte -1024 x 1024 bytes = 1,048,576
bytes
 GB - Gigabyte - 1024 x MB = 1,073,741,824 bytes

Output Devices

Monitor - displays output in pixels - picture
elements
– cathode ray tube (CRT)
– liquid crystal display (LCD)
– resolution measured in pixels
CGA - 320 x 200
 VGA - 640 x 480
 SVGA - 1024 x 768


Graphics Adapter - Display Card - Display
Adapter
– connects monitor to motherboard
– monitor must support its resolution
Printers
Output from printer called “hard copy”
 Speed measured in ppm - pages per minute - 4, 6,
8, 12
 Three types:

– dot-matrix : pins striking ribbon make dots on paper

9-pin or 24-pin vertically
– Ink-jet : tiny dots of ink sprayed on paper
black or color
 color should have separate black cartridge to save expensive
color

– Laser jet : laser bonds black powder (toner) to paper

quality in dots per inch (dpi) 300 dpi standard, 600 dpi better
Storage Devices

Diskettes - most common 3 1/2” HD - 1.44 MB
– write protection - window on disk to prevent writing
Hard Disks - common 540 MB to 4.2 GB
 CDs - 680 MB or more

– transfer at 150 K per second
– double-speed - 300 K per second - sound and video
– quad-speed - 600 K per second - true multimedia

Tape - usually for backup
– slow, sequential access
Communications Hardware

Modem or Fax modem
–
–
–
–

transmit digital data over analog phone lines
speed measured in bits per second
9600 bps; 14,400 bps; 28,800 bps; 33,600 bps; 52 Kbps
fax capabilities allow sending and receiving of faxes
Network Interface Card
– interface between computer and network
– must worry about network protocols and cable types
– typically ethernet card with coaxial or twisted-pair
connectors
Computer Software
instructions for computer to accomplish a task
1. Systems software - run fundamental operations

–
–
–
–
loading programs and data into memory
executing programs
saving data on disk
performing I/O
2. Applications software - applies computer to
goals
– word processing, spreadsheet, database, graphics
Systems Software

Operating System - provides system control
– DOS - Disk Operating System
MS-DOS or PC-DOS
– control computer via a series of commands

Operating environments - between OS and user
–
–
–
–
graphical interface for DOS commands
Windows 2.0, 3.0, and 3.1 - run above DOS
Windows ‘95 and Windows NT - run without DOS
many programs now require a Windows environment
to run
Applications Software

Word processing software
– electronically create, edit, format, and print documents
– move paragraphs, check spelling, create tables and
columns
– modify margins, correct typos, preview printing
– Microsoft Word, WordPerfect

Electronic Spreadsheet
– perform calculations with numbers in rows and
columns
– type data, enter formulas, calculate results, create
graphs
– Microsoft Excel, Borland’s Quattro Pro, Lotus 1-2-3
Applications Software II

Database software - manage and manipulate info.
– search, sort, select, delete, and update a database
– create reports, answer questions, create entry forms
– Microsoft Access, Borland’s Paradox

Graphics software - create illustrations, diagrams,
graphs and charts
– draw lines, boxes, circles, fill and erase, enlarge, print
– include clipart - predrawn images
– Microsoft Paintbrush, CorelDRAW, Harvard Graphics