Chapter Four
Software Basics: The Ghost in the Machine
Chapter Outline
• Processing with Programs
• Application Software: Tools for Users
• System Software: The HardwareSoftware Connection
• The User Interface: The HumanMachine Connection
 1999 Addison Wesley Longman
4.2
Processing with Programs
• Software programs:
– Are invisible and complex
– Must be clear
– Must be free of errors
– Are a set of instructions
that tell a computer what
to do
 1999 Addison Wesley Longman
4.3
A Fast, Stupid Machine
• Computers:
– Have limited capabilities
– Can only do basic
mathematics and logical
comparisons
– Must be instructed with
programs what to do
 1999 Addison Wesley Longman
4.4
The Language of Computers
• Programmers begin with an algorithm,
which is:
– A set of step-by-step instructions (written in
a natural language, e.g., English)
• Algorithms are translated into the
vocabulary of a programming language
 1999 Addison Wesley Longman
4.5
Flow Chart (I)
•
•
•
•
•
process
decision
terminal
joint
flow line
 1999 Addison Wesley Longman
4.6
Flow Chart (II)
• predefined procedure
• input
• output
• I/O
 1999 Addison Wesley Longman
4.7
Control Structures
• sequential execution ( concatenation )
• conditional execution ( alternation )
• looping ( iteration )
 1999 Addison Wesley Longman
4.8
Top-Down Structure Design
•
•
•
•
define the problem
design the algorithm as procedures
refine the procedures into pseudo code
code the program
 1999 Addison Wesley Longman
4.9
Programming Languages
• Programming languages bridge the gap
between the natural language of the
human and the numeric codes
(zeros and ones)
understood by the
computer
• Examples include:
– COBOL, BASIC, and C++
 1999 Addison Wesley Longman
4.10
Programming Languages
• low level languages
– machine language
– assembly language (symbolic language)
• high level languages
– machine independent
– problem oriented
– familiar notations
 1999 Addison Wesley Longman
4.11
High Level Languages
•
•
•
•
•
1957
1960
1965
1971
1972
Fortran
COBOL
BASIC
Pascal
C
 1999 Addison Wesley Longman
Z=X+Y
ADD X TO Y GIVING Z
Z=X+Y
z:=x+y;
z=x+y;
4.12
High Level Languages
• 1980
• 1985
• 1990
Ada
C++
Java
Sorting ( Ordering )
• internal sort
• external sort
 1999 Addison Wesley Longman
4.14
Internal Sort
• straight
– exchange ( bubble sort )
– insertion sort
– selection sort
• advanced
– shell sort
– heap sort
– quick sort
 1999 Addison Wesley Longman
4.15
Bubble Sort
•
•
•
•
•
44 55 12 42 94 18 06 67
06 44 55 12 42 94 18 67
06 12 44 55 18 42 94 67
06 12 18 44 55 42 67 94
06 12 18 42 44 55 67 94
 1999 Addison Wesley Longman
4.16
Bubble Sort
•
•
•
•
•
•
•
•
•
•
1000
1010
1020
1030
1040
1050
1060
1070
1080
1090
REM bubblesort subroutine
FOR M = 2 to N
FOR I=N to M step -1
IF A(I-1) <= A(I) THEN 1070
TEMP = A(I-1)
A(I-1) = A(I)
A(I) = TEMP
NEXT I
NEXT M
RETURN
 1999 Addison Wesley Longman
4.17
Insertion Sort
•
•
•
•
•
•
•
44 55 12 42 94 18 06 67
44 55
12 44 55
12 42 44 55 94
12 18 42 44 55 94
06 12 18 42 44 55 94
06 12 18 42 44 55 67 94
 1999 Addison Wesley Longman
4.18
Insertion Sort
• procedure straightinsertion
•
var i,j: index; x:integer;
• begin
•
for i := 2 to n do begin
•
x := a[i]; a[0] := x; j := i-1;
•
while x< a[j] do
•
begin a[j+1] := a[j]; j := j-1 end;
•
a[j+1] := x;
•
end
• end;
 1999 Addison Wesley Longman
4.19
Selection Sort
•
•
•
•
•
•
44 55 12 42 94 18 06 67
06 55 12 42 94 18 44 67
06 12 55 42 94 18 44 67
06 12 18 42 94 55 44 67
06 12 18 42 44 55 94 67
06 12 18 42 44 55 67 94
 1999 Addison Wesley Longman
4.20
Selection Sort
• for (i=1;i<n; i++) {
•
min = i;
•
for( j= i+1; j<n; j++)
•
if (a[j] < a[min]) min= j;
•
temp= a[i];
•
a[i] = a[min];
•
a[min] = temp;
• };
 1999 Addison Wesley Longman
4.21
Shell sort
•
• 4 sort
• 2 sort
• 1 sort
44 55 12 42 94 18 06 67
44 18 06 42 94 55 12 67
06 18 12 42 44 55 94 67
06 12 18 42 44 55 67 94
• each pass profits from previous pass
• diminishing increment yields better result
 1999 Addison Wesley Longman
4.22
Heap sort
•
•
•
•
•
44 55 12 42 | 94
44 55 12 | 42 94
44 55 | 06 42 94
44 | 42 06 55 94
| 06 42 12 55 94
•
•
•
12 42 18 55 94 67 44 | 06
18 42 44 55 94 67 | 12 06
42 55 44 67 94 | 18 12 06
 1999 Addison Wesley Longman
18
18
18
18
18
06
06
12
12
44
67
67
67
67
67
4.23
Quick sort
•
•
44 55 12 42 94 06 18 67
18 06 12 42 94 55 44 67
 1999 Addison Wesley Longman
4.24
Application Software:
Tools for Users
• Software applications include:
– Consumer software
– Integrated software
– Vertical-market and
custom software
 1999 Addison Wesley Longman
4.25
Consumer Applications
• There are thousands of different
consumer software titles
• Consumer software differs based on:
– Documentation
– Upgradability
– Compatibility
– Warranty
– Extent of ownership/license
 1999 Addison Wesley Longman
4.26
Documentation
• Documentation includes:
– Printed tutorial and reference manuals
that explain how to use the software
– On-line manuals and help screens
which offer immediate help
to the user
 1999 Addison Wesley Longman
4.27
Upgrades
• Rather than buy the latest version and
discard your old one, often you can pay
a fee to the software maker and
upgrade the old version to the new one
• Newer versions of a software
company’s product usually have
additional features and fewer bugs
 1999 Addison Wesley Longman
4.28
Compatibility
• Compatibility means the software will
function properly with the hardware,
operating system, and any peripherals
• To date, there is no industry standard
that software must follow
 1999 Addison Wesley Longman
4.29
Warranty
• Buyer beware!
• Software manufacturers limit their
liability for software problems by
selling their software “as is”
• Error-free software
does not exist
 1999 Addison Wesley Longman
4.30
Ownership/Licensing
• Three categories:
– Purchased software grants you a license to
use the software as the software company
tells you
– Shareware software is free for the trying,
but a nominal fee is to be paid to the
programmer if you continue to use it
– Public domain software is legally free and
cannot be owned or licensed
 1999 Addison Wesley Longman
4.31
Integrated Applications and Suites:
Multipurpose Software
• Multipurpose software that includes
most of these modules:
– Word processing
– Database
– Spreadsheet
– Graphics
– Telecommunications
 1999 Addison Wesley Longman
4.32
Integrated Software: Advantages
• Costs less than buying the applications
individually
• Data is easily transferred between
modules
• Commands used in each module are
usually the same
• Usually there is a seamless integration
of the modules
 1999 Addison Wesley Longman
4.33
Vertical-Market and
Custom Software
• Job-specific software:
– Medical billings
– Library cataloging
– Restaurant management
– Single-client software needs
 1999 Addison Wesley Longman
4.34
System Software:
The Hardware-Software Connection
• Operating Systems
• Language
Processors
• Utility Programs
 1999 Addison Wesley Longman
4.35
Language Processors
• Assemblers
• Compilers
• Interpreters
 1999 Addison Wesley Longman
4.36
What the Operating System Does
• The operating system controls:
– Communication with peripherals
– Coordination of concurrent processing
– Memory management
– Monitoring of resources and security
– Management of programs and data
– Coordinating network communications
 1999 Addison Wesley Longman
4.37
Operating System
• to make users comfortable
• to make machines efficient
• MS-DOS
– single user, single-task
• WINDOWS
– single user, multi-task
• Unix
– multi user, multi-task
 1999 Addison Wesley Longman
4.38
Microsoft O.S.
• 1980 MS-DOS
– text mode
• 1990 MS-Windows 3.0
– graphic mode
– multi-tasking
• 1995 MS-Windows 95
– native O.S.
– plug & play
– network management
 1999 Addison Wesley Longman
4.39
Microsoft O.S.(II)
• 1998 MS-Windows 98
– Web integration
– support multi-medium
• 2000 MS-Windows Me
– more reliable
 1999 Addison Wesley Longman
4.40
Utility Programs
• Utility software controls tasks such as:
– repairing damaged files
– making it easy for users to copy files from
one storage device to another
– translating files so different
software can read them
– guarding against viruses
 1999 Addison Wesley Longman
4.41
The User Interface:
The Human-Machine Connection
• The user interface is what the user sees
on the screen and interacts with
• Two major user interface types:
– Character-based interface
– Graphical user interface
 1999 Addison Wesley Longman
4.42
A Character-Based User Interface:
MS-DOS
• This is a disk operating system in which
the user interacts with characters
– letters
– numbers
– symbols
 1999 Addison Wesley Longman
4.43
A Character-Based User Interface:
MS-DOS
• MS-DOS™ is the most widely used
general-purpose operating system
• Features include:
– Command-line interface (commands are
typed)
– Menu-driven interface (commands are
chosen from on-screen lists)
 1999 Addison Wesley Longman
4.44
Graphical User Interfaces:
Macintosh
• This is a disk operating system in which
the user interacts with the computer by
using a pointing device (e.g. a mouse)
• As early as 1984, the
Macintosh™ computer
was designed with this
interface in mind
 1999 Addison Wesley Longman
4.45
Graphical User Interfaces:
Windows
• In 1995,
Windows 95™
was released as a
graphical user
interface for IBM™
computers and
their compatibles
 1999 Addison Wesley Longman
4.46
Why WIMP Won
• Windows, Icons, Menus, and Pointing
devices
• In this graphical user interface, the
cursor of the pointing device (mouse)
appears on the screen and can be used
to point to icons, work within windows,
and select from menus
 1999 Addison Wesley Longman
4.47
Tomorrow’s User Interfaces
• Future interfaces will probably:
– Make individual applications obsolete
– Support natural languages
(talk to the machine and it
talks back)
– Include artificial intelligence
and agents that fit our needs
– Be based on virtual reality
(data in three-dimensional physical space)
 1999 Addison Wesley Longman
4.48
Rules of Thumb:
Computer Consumer Concepts
Before you buy, you should consider:
•
•
•
•
•
•
Cost
Compatibility
Capacity
Customizability
Capability
Connectivity
 1999 Addison Wesley Longman
• Convenience
• Company
• Purchasing Curve
4.49
Cost
• Before you buy:
– Determine what you can afford
– Allow for “extras”
– Join a user group or
talk with other computer
and software owners
 1999 Addison Wesley Longman
4.50
Compatibility
• Before you buy, make sure you know:
– What is the right computer and software for
what you want to do
– If the computer and software you will need
work well together
 1999 Addison Wesley Longman
4.51
Capacity
• Before you buy, make sure you know:
– How much computer power
you are going to need
– If the processor will be able
to handle your demands
– If you will be able to
upgrade later on
 1999 Addison Wesley Longman
4.52
Customizability
• Before you buy, make sure you know:
– If your computer can be customized to fit
your needs (such as video editing)
 1999 Addison Wesley Longman
4.53
Capability
• Before you buy, make sure you know:
– Which computer is
the right tool for you
– If the computer and
software will be able
to meet your demands
today and years from
now
 1999 Addison Wesley Longman
4.54
Connectivity
• Before you buy, make sure you:
– Have included a high-speed modem or some
other network connection
– Can take full advantage of the
communication capabilities of your computer
 1999 Addison Wesley Longman
4.55
Convenience
• Before you buy, make sure you
determine:
– Whether portability or permanent
connection of peripherals is
important
– Which kind of user interface will
help you do your work easier
– If you should have the same
machine as people around you
 1999 Addison Wesley Longman
4.56
Company
• Before you buy, make sure you know:
– if you are buying from
a reputable company
– if parts and service will
be available if needed
 1999 Addison Wesley Longman
4.57
Purchasing Curve
• Most models of personal computers
seem to have a useful life span of just a
few years
• Before you buy, make sure you know:
– how new or old the computer is that you
want to buy
– not to buy a brand new computer model
– not to buy an “obsolete” computer model
 1999 Addison Wesley Longman
4.58