Software Life Cycle

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Software Life Cycle
Requirements Gathering, Problem definition
Analysis and Design (Programming techniques)
Coding
Testing
Implementation and Maintenance
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Coding and Testing
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How to develop a program

• Identify the steps and execution sequence.
• Every program consist of mainly three parts
• Input, Processing and Output
• Example Add two numbers
• Steps
• Read/Input two numbers
• Add these two numbers
• Display/Output the result of addition
• Algorithm Steps written in English language.
• Program Algorithm written in a specific high
  level language.

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Algorithm

• An Algorithm is a solution to a problem that is
  independent of any programming language.
• An Algorithm is
• a finite sequence of steps
• each step shall be clearly stated and
  understandable
• for each input, it shall terminate in finite time
  with output
• How we solve the problem with Computer?

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Program and Programming

• Program
• A set of instruction written in a programming
  language that a computer can execute so that the
  machine acts in a predetermined way.
• Program solves a problem
• Before writing a program
• Have a thorough understanding of the problem
• Carefully plan an approach for solving it.
• Programming
• The Process of providing instructions to the
  computer that tells the processor what to do.

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Algorithms Programs

• An Algorithm is a solution to a problem that is
  independent of any programming language. Wh
  ile
• A program is an algorithm expressed using a
  specific set of instructions from any programming
  language.

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Algorithm Example

• Maximum of two numbers
• Steps
• Read/input two numbers
• Compare two numbers
• Print the Greater number
• Average of three numbers
• Steps
• Read/input three numbers
• Add three numbers
• divide the sum by 3.
• Print the result of divison

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Pseudocode

• This is a common notation for writing algorithms.
• Mixture of English language statement and a
  programming language( like C) code.
• It is an intermediate step in writing a program.
• Not actually executed on computers.
• Standard mathematical notations like
  exponents,square-root symbols etc. are allowed in
  pseudocode.

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Rules for pseudo code

• The beginning and end of a pseudo code is marked
  with keywords START and STOP.
• Every variable should be initialized in the
  beginning only using INITAILZE
• Values from user should be accepted using keyword
  READ, and should be display using WRITE.
• All alphanumeric values should be enclosed in
  single or double quotes.
• All the nested loops are for-do-done,
  while-do-done
• All the control structures are if-then-else-fi,
  switch-case.

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Examples

• Pseudo code to find out the sum of all
• odd numbers in the range 1 to 10.
• START
• INITIALIZE a10, sum0,i
• for i1 to 10 do
• Read ai
• if (condition) then
• Calculate sumsumai
• done
• Write sum
• STOP

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Examples

• Pseudo code to find out the maximum number from
  20
• given numbers.
• START
• INITIALIZE a20,max,i
• for i1 to 20 do
• Read ai
• done
• maxa1
• for i2 to 20 do
• if aigtmax then
• Assign maxai
• done
• Write max
• STOP

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Practice Example

• Write an algorithm for the given problem
• 10 students of a class appears for a test in
  three
• subjects. Each test is out of 100 marks. The
  percentage
• of each student has to be calculated and
  depending on
• the percentage calculated, grades are given below

Percentage Grade
gt 80 A
60-79 B
lt59 C
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Flowchart

• Graphical representation of an algorithm
• Components
• Arrows/lines Flow of control
• Parallelogram Indicates input and output
  operations
• Rectangle symbol (action symbol) Indicates any
  type of action/computational step
• Oval symbolIndicates the beginning or end of a
  program or a section of code
• Diamond Decision

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Flowchart Notations
Arrows
Diamond
Parallelogram
Oval
Rectangle
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(No Transcript)
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Example Add two Numbers
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Draw both flow chart and pseudo code

• You are required to calculate area of circle and
  rectangle.
• Accept from user the figure and then accordingly
  calculate and display.

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Pseudo code

• START
• INITIALIZE FIG, area0
• READ FIG
• IF FIG circle
• CALL CIR_ROUTINE
• ELSE
• IF FIGrectangle
• CALL RECT_ROUTINE
• ELSE
• GOTO label 1
• ENDIF
• ENDIF
• WRITE area of figure, area
• STOP

label 1
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• CIR_ROUTINE
• INITIALIZE radius0
• READ radius
• CALCULATE area 3.14 radius radius
• RETURN to Calling procedure

RECT_ROUTINE INITIALIZE length0, width0
READ length,width CALCULATE area
lengthwidth RETURN to Calling procedure
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Flow Chart
READ FIG
START
FIG?
READ LENGTH WIDTH
rectangle
other
circle
READ RADIUS
AREALENGTH WIDTH
PRINT AREA
AREA3.14RADIUS RADIUS
STOP
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Problems

• GCD of three numbers
• Calculate 2n
• Roots of equation ax2bxc0
• Largest of N numbers
• Generate the fibonacci series