Program Development Life Cycle (PDLC)

The Program Development Life Cycle (PDLC) is a systematic sequence of steps followed by a programmer to analyze a problem, design a solution, develop the program, test it, and maintain it.

A computer program generally performs three basic tasks:

Input → Processing → Output

For example, in a program to calculate the average of three marks:

• Input: Three marks
• Processing: Calculate their average
• Output: Display the average

Developing such a program requires more than simply writing code. The programmer follows the Program Development Life Cycle.

Stages of Program Development Life Cycle

1. Problem Analysis

The programmer first understands and analyzes the problem.

This includes:

• Identifying what the problem requires
• Identifying the input
• Identifying the required output
• Determining the processing required
• Considering constraints and possible solutions
• Selecting the most suitable solution

Example:
For calculating the average of three marks:

Input:     Three marks
Process:   Add the marks and divide by 3
Output:    Average marks

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2. Program Design

Once the solution is selected, it is represented in a form that can be converted into a program.

The main tools used are:

a. Algorithm

A step-by-step description of the solution written in simple, English-like language.

b. Flowchart

A graphical representation of the algorithm using standard flowchart symbols.

c. Pseudocode

A structured, programming-like representation of the solution that is independent of any particular programming language.

Thus:

Problem
   ↓
Algorithm
   ↓
Flowchart / Pseudocode
   ↓
Program Code

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3. Program Development

The designed solution is converted into a computer program using a programming language such as Python, C, Java, etc.

The program is then compiled or interpreted and checked for errors.

One important type of error is a syntax error, which occurs when the rules or grammar of the programming language are not followed.

Example:

print("Hello"

The missing closing parenthesis causes a syntax error.

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4. Testing and Debugging

After development, the program is executed with different inputs to determine whether it produces the expected output.

If the program produces incorrect results, the programmer identifies and corrects the errors. This process is called debugging.

For example:

Input:  10, 20, 30
Expected average: 20
Actual average:   25

The programmer must find and correct the logical error responsible for the incorrect result.

Common errors include:

• Syntax errors – Violation of programming language rules
• Logical errors – Program runs but produces incorrect results
• Runtime errors – Errors that occur while the program is executing

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5. Program Documentation

The program is documented so that other programmers and users can understand, use, modify, and maintain it.

Documentation may include:

• Purpose of the program
• Description of inputs and outputs
• Explanation of the algorithm
• Important details about the code
• Instructions for using the program

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6. Program Maintenance

After the program is installed and used, it may require changes or improvements.

Maintenance may involve:

• Fixing newly discovered errors
• Updating the program
• Adding new features
• Improving performance
• Adapting the program to new requirements or environments

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Summary of PDLC

Stage	Main Activity
1. Problem Analysis	Understand the problem and identify input, processing, and output
2. Program Design	Develop algorithm, flowchart, and pseudocode
3. Program Development	Convert the design into program code
4. Testing & Debugging	Test the program and correct errors
5. Documentation	Document the program and its working
6. Maintenance	Modify, update, and improve the program after deployment

Overall Process

Problem
   ↓
Problem Analysis
   ↓
Program Design
   ↓
Program Development
   ↓
Testing & Debugging
   ↓
Documentation
   ↓
Maintenance
   ↺

In simple words: The Program Development Life Cycle provides a systematic approach to developing reliable computer programs, rather than directly jumping from a problem to writing code.