software life cycle use requirements gathering, problem definition analysis and design (programming...
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Software Life CycleSoftware Life Cycle
Use
Requirements Gathering, Problem definition
Analysis and Design (Programming techniques)
Coding
Testing
Implementation and Maintenance
What
How
Do it
Test
Coding and TestingCoding and Testing
Write Program
Compile Program
Run and Test Program
Submit Program
Success
Correct Errors
Correct Errors
Correct Errors
Errors
Errors
Errors
How to develop a program 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 numbersSteps1. Read/Input two numbers2. Add these two numbers3. Display/Output the result of addition
• Algorithm : Steps written in English language.• Program : Algorithm written in a specific high
level language.
AlgorithmAlgorithm• 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?
Program and Programming 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.
Algorithms & ProgramsAlgorithms & Programs
• An Algorithm is a solution to a problem that is independent of any programming language.
While
• A program is an algorithm expressed using a specific set of instructions from any programming language.
Algorithm ExampleAlgorithm Example
• Maximum of two numbers Steps:
1.Read/input two numbers2.Compare two numbers3.Print the Greater number
• Average of three numbers Steps:
1.Read/input three numbers2.Add three numbers3. divide the sum by 3. 4.Print the result of divison
PseudocodePseudocode
– 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.
Rules for pseudo codeRules 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.
ExamplesExamples
Pseudo code to find out the sum of all odd numbers in the range 1 to 10.STARTINITIALIZE a[10], sum=0,ifor i=1 to 10 do Read a[i]; if (condition) then Calculate sum=sum+a[i]; doneWrite sum;STOP
ExamplesExamplesPseudo code to find out the maximum number from 20 given numbers.
STARTINITIALIZE a[20],max,i;for i=1 to 20 do Read a[i];donemax=a[1];for i=2 to 20 do if a[i]>max then Assign max=a[i]; doneWrite max;STOP
Practice ExamplePractice ExampleWrite 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
> =80 A
60-79 B
<=59 C
FlowchartFlowchart– 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 symbol:Indicates the beginning or end
of a program or a section of code• Diamond: Decision
Flowchart NotationsFlowchart Notations
Arrows
Parallelogram
Rectangle
Diamond
Oval
Example: Add two NumbersExample: Add two Numbers
READ A,B
C=A+B
PRINT C
START
STOP
Draw both flow chart and pseudo Draw both flow chart and pseudo codecode
You are required to calculate area of circle and rectangle.
Accept from user the figure and then accordingly calculate and display.
Pseudo codePseudo code
STARTINITIALIZE FIG, area=0;READ FIG ;IF FIG = “circle”
CALL CIR_ROUTINE ;ELSE
IF FIG=“rectangle” CALL RECT_ROUTINE ;
ELSE GOTO label 1;ENDIF
ENDIFWRITE “ area of figure”, area;STOP
label 1:
CIR_ROUTINE INITIALIZE radius=0; READ radius; CALCULATE area = 3.14 *
radius * radius; RETURN to Calling
procedure
RECT_ROUTINE
INITIALIZE length=0, width=0;
READ length,width;
CALCULATE area = length*width;
RETURN to Calling procedure
Flow ChartFlow Chart
READ FIG
AREA=3.14*RADIUS * RADIUS PRINT AREA
FIG?
circle
rectangle
READ RADIUS
READ LENGTH & WIDTH
AREA=LENGTH * WIDTH
START
STOP
other
ProblemsProblems• GCD of three numbers• Calculate 2n
• Roots of equation ax2+bx+c=0• Largest of N numbers• Generate the fibonacci series
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