INFO Martin van Bommel

What is a Computer? v Computer - electronic device that accepts input, performs calculations, and produces the required results v Hardware - components of computer system that you can see and touch e.g. keyboard, screen, disk drive, printer, circuit board v Software - list of instructions for computer to perform a specific task e.g. operating system, word processor, Windows

Input - Processing - Output v Input - what you type, read, or enter into computer – Devices - keyboard, mouse, scanner, sensors v Processing - changing the input data via formatting, sorting, and calculations – Devices - components on motherboard, CPU, ALU, memory v Output - results of computer processing – Devices - screen, printer, plotter, signals v Storage - save information for later processing –Devices - memory, diskette, hard disk, tape

Types of Computers v Microcomputers or Personal Computers (PCs) –inexpensive - $500 - $15,000 –small enough to fit on desk –CPU contained on single chip v Minicomputers and Mainframes –$15,000 - millions –too large for desktop –larger capacity for storing and manipulating data v Servers –Usually fast microcomputers or small minicomputers –Lots of memory and disk space

Processing Hardware v Microprocessor or Central Processing Unit (CPU) –integrated circuit chip on the motherboard –performs arithmetic and logical operations v Input/Output Interface Cards (I/O Cards) –provide connection between CPU and I/O devices v Floppy and Hard Disk Drives –storage external to the motherboard v Memory –temporary storage on the motherboard

Data Representation v bit - binary digit - 0 or 1 v byte - eight bits v ASCII code - each character represented by 8 bits Number Binary Character ASCII A A B B Z

Memory v ROM - Read-Only Memory –permanent memory installed by manufacturer –initial instructions for computer on start-up v RAM - Random-Access Memory –temporary storage for data and instructions –lost when power off v Byte = 8 bits v K - Kilobyte bytes v MB - Megabyte x 1024 bytes = 1,048,576 bytes v GB - Gigabyte x MB = 1,073,741,824 bytes

Output Devices v Monitor - displays output in pixels - picture elements –cathode ray tube (CRT) –liquid crystal display (LCD) –resolution measured in pixels u CGA x 200 u VGA x 480 u SVGA x 768 v Graphics Adapter - Display Card - Display Adapter –connects monitor to motherboard –monitor must support its resolution –contains memory to store image for faster processing

Printers v Output from printer called “hard copy” v Speed measured in ppm - pages per minute - 4, 6, 8, 12 v Three types: –dot-matrix : pins striking ribbon make dots on paper u 9-pin or 24-pin vertically –Ink-jet : tiny dots of ink sprayed on paper u black or color u color should have separate black cartridge to save expensive color –Laser jet : laser bonds black powder (toner) to paper u quality in dots per inch (dpi) 300 dpi standard, 600 dpi better

Storage Devices v Diskettes - most common 3 1/2” HD MB –write protection - window on disk to prevent writing v Hard Disks - common 540 MB to 4.2 GB v CDs MB or more –transfer at 150 K per second –double-speed K per second - sound and video –quad-speed K per second - true multimedia v Tape - usually for backup –slow, sequential access

Communications Hardware v 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 v 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 v 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 v Operating System - provides system control –DOS - Disk Operating System MS-DOS or PC-DOS –control computer via a series of commands v Operating environments - between OS and user –graphical interface for DOS commands –Windows 2.0, 3.0, and run above DOS –Windows ‘95 and Windows NT - run without DOS –many programs now require a Windows environment to run

Applications Software v 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 v 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 v 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 v 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