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What is a Computer?

It is device that performs
(a) Arithmetic operations (addition, subtraction, multiplication,
and division)
(b) Logical operations (comparisons--equal, less than, greater than, etc.)

It is the Central Processing Unit (CPU)


What is a Computer System?
Hardware -- CPU, Input/Output devices, Storage devices, etc.
Software -- Programs
Data
Trained People
Procedures


What does a Computer System Perform?
Input
Process
Output
Storage
Communication


Data Vs. Information

Data: Raw facts and Figures--Name, Hours, Pay rate, lettuce, tomatoes
Text data, numeric data, voice data, video data, etc.

Information: Processed data, Take home pay, Salad

Data and Information are relative words


Program

A series of meaningful instructions to solve a problem

Programs should have proper syntax and semantics
Syntax-- grammar, punctuation, etc. The monkey ate a banana.
Semantics -- meaning of the statement. The banana ate a monkey.

Programs are written in programming languages
Programming languages are not context sensitive like natural languages
The wild animal trainer was in town.
I saw a man on the hill with a telescope.


Types of Programming Languages
Machine--Binary Code
Low-Level
High-Level
Very-High Level
Object Oriented Programming (OOP)


Low-Level
Basic Assembly Language (BAL)
Machine specific
Faster execution
One to one relation between source code and object code except macros
Lotus 123, DOS etc are written in Assembly Language

Sample program
L 5, NUM1
L 6, NUM2
AR 5, 6
ST 5, RESULT
PUT RESULT


High-Level --English like
QBASIC, FORTRAN, COBOL, C, etc.
Machine independent.
Procedure oriented--”how” is emphasized over “what”
one to many ratio between source code and object code


Very High-Level
Fourth Generation (4GL), Focus, SQL, etc.
Problem oriented--”what” is emphasized over “how”

Object Oriented Programming Languages (OOP)
Ex: Small Talk, Actor (pure)
C++ (Hybrid)
Characteristics
Encapsulation
Inheritance
Polymorphism

A sample program in C++
10/10/96/ A sample C++ program illustrating output.
include <stream.h>
main ()

{ cout << “C++ is an improved c.\n”;
}


Programmer
Application Programmer--develops application programs
System Programmer-- develops systems programs
Maintenance programmer--maintains, updates programs


Computer Memory

Main Memory--temporary or volatile, contents disappear when the
power is switched off. (Random Access Memory, RAM)

Secondary memory -- tapes, disks, etc.


Hardware
Tangible devices, equipment, etc.
Input hardware
Processing hardware
Output hardware
Storage hardware
Communication hardware


Software
Intangible, programs
Systems
Applications


Why Computers?

Faster
Microsecond (one millionth of a second), nanosecond (one billionth
of a second), picosecond (one trillionth of a second ) speeds.

Huge storage capacity--
Megabyte (one million bytes or characters) or about 500 pages to
gigabytes (one billion bytes) or even a terabyte (trillion bytes)

Accurate

Reliable

Cost effective


Types of Computers
Microcomputers IBM 486, or a MAC
Workstations SUN, DEC
Minicomputers VAX
Mainframes -- IBM 4381
Supercomputers --Cray Y-MP, MPP 2568


Where are they used?
Business
Education
Government
Entertainment
Everywhere


Social Impact
Unemployment
Privacy
Crime
Dehumanizing
Errors


Why errors?
Program errors
Input errors (GIGO)
Communication problems
Poor Documentation
Poor Cost Estimates
Cyberphobia
Inadequate testing


Summary
What is a Computer?
What is a Computer system?
What does a Computer System Perform?
Data Vs. Information
Programs, Programming Languages, programmers
Computer Memory: (a) Primary, (b) Secondary
Computer Hardware & Software
Why Computers?, Types of Computers
Uses of Computers
Social Impact, Computer Errors