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Computer and
Information Science
Chapter 1.2
Computer Software
Agenda
Application Software
 Operating Systems

Software
Software is the programs and data that
a computer uses.
 Programs are lists of instructions for
the processor.
 Data can be any information that a
program needs: character data,
numerical data, image data, audio
data, and countless other types.

– Digitizing :The process of taking a visual image, or
audio recording and converting it to a binary form
for the computer.
Types of Programs
Imagine that you have just turned
on your computer and have not yet
started any application. Are any
programs running?
 Two types of software

– Application software
– System software/Operating systems
Why do we need an OS?

What are the goals of an Operating
System?
– The primary goal of an Operating System is
to make the computer system convenient to
use.
– The secondary goal is to make the computer
system efficient to use.
An Operating System
It underlies all other software.
 It acts as an interface between a user of a
computer and the computer hardware
 It manages and coordinates computer
system resources ( CPU, memory, file
system, I/O devices)
 It provides the user Interface that is:

– How can something as simple-minded as a processor and
memory present you with something as rich as the Mac or
Windows GUI?
Operating system services ...
Control
basic input
and output
Allocate
system
resources
Manage
storage
space
Operating Systems
Operating system services ...
Detect
equipment
failure
Maintain
security
System calls
• You ask MS Word to OPEN a document
– File menu/Open…
– WHAT WILL YOU SEE?
– What really just happened in the box?
WORD called on O.S. to present
you with that file list!
O.S. must look at:
1. Disk Directory (list of filenames)
2. File Allocation Table (FAT)…. (list
of file locations: starting
position/cluster number on the disk)
Multi-tasking

>1 program or person can share
computer resources.
– CPU is idle ~90% of time, waiting for user input !
– One program active; Others running in the
background

OS must protect each program’s memory area to ensure
that instructions and data don’t “leak” into an area
allocated to another program. If it fails, programs can
crash…more shortly!
Booting and BIOS


When a computer is started up, the
hardware will automatically load the
operating system and start it running. This
process is called booting.
BIOS is the boot program on a computer,
and controls the computer from the time
you start it up until the operating system
takes over. When you turn on a PC, the
BIOS first conducts a basic hardware
check, called a Power-On Self Test (POST),
to determine whether all of input/output
devices are present and working. Then it
loads the operating system into your
computer's RAM.
ROM (Read-only-Memory)
ROM refers to computer memory
chips containing permanent or
semi-permanent data. Unlike RAM,
ROM is non-volatile; even after you
turn off your computer, the
contents of ROM will remain .
 BIOS is stored in a ROM.

Various Operating Systems
Windows : Developed by Microsoft
XP, Vista, windows7
 Unix: Developed by AT&T for large
companies
 Linux: Open Source version of
Unix
 Mac OS: only for Mac hardware
e.g. Snow Leopard

Microcomputer Operating Systems
Why is it important for me to know which operating system
is on my computer?
UNIX
SunOS UNIX
UNIX features a command
line interface. Designed for
minicomputers but is now
also available for micros
and mainframes.
login: smith
Password:
Last login: Oct 15 17:42:09 from tserv1.edu
SunOS Release 4.1.1 #1: Wed Mar 20 11:24:14 AST 1991
You have mail.
%_
The UNIX prompt
IMPORTANT !
WHAT HAPPENS when you SHUT DOWN
improperly? Why should you care?
“Shutting down incorrectly is a little like
stopping your car by driving it into a wall.
It works, but it can cause some damage.”
Computer terms bingo
Follow the link
http://www.wcu.edu/ceap/Kirk/Merlot
_Resources/KnowYourComputerTe
rms.swf
