Programming Logic

1. What is Programming Logic?

Before writing a program in C, Java, Python or another programming language, it is useful to first think about the solution.

In simple words:

Logic Building Tools

2. Algorithm

Characteristics of a Good Algorithm

• It should have a clear beginning and ending.
• Steps should be arranged in the correct order.
• Each step should be clear and unambiguous.
• It should eventually produce the required result.
• It should be easy to convert into a programming language.

Example: Store and Display a Number

Problem: Write an algorithm to store the number 25 and display it.

Algorithm – Detailed Version

1. Start the program.
2. Reserve some memory space to store a number.
3. Store the value 25 in the allocated memory.
4. Display the value stored in the memory.
5. Stop the program.

Algorithm Using a Variable Name

1. Start the program.
2. Reserve memory to store a number and give the memory location the name a.
3. Store the value 25 in a.
4. Display the value stored in a.
5. Stop the program.

3. Pseudocode

Pseudocode is sometimes called “false code” because it looks similar to programming code but does not follow the exact syntax of a particular programming language.

Algorithm vs Pseudocode

Pseudocode for Storing and Displaying a Number

START

DECLARE a

a := 25

WRITE "Value of a = ", a

STOP
        

4. From Pseudocode to a Real Program

The same logic can be implemented in different programming languages. The algorithm remains essentially the same, but the syntax changes.

C Language

#include <stdio.h>

int main()
{
    int a;

    a = 25;

    printf("a = %d", a);

    return 0;
}
        

Java

public class Sample
{
    public static void main(String[] args)
    {
        int a;

        a = 25;

        System.out.println("a = " + a);
    }
}
        

Python

a = 25
print("a =", a)
        

5. Example 1 – Sum of Two Numbers

Problem: Calculate and display the sum of any two numbers.

Algorithm

1. Start.
2. Declare variables a, b and sum.
3. Read the values of a and b.
4. Calculate sum = a + b.
5. Display sum.
6. Stop.

Pseudocode

START

DECLARE a, b, sum

READ a
READ b

sum := a + b

WRITE "Sum = ", sum

STOP
        

6. Example 2 – Area of a Rectangle

Problem: Calculate and display the area of a rectangle for a given length and breadth.

Algorithm

1. Start.
2. Declare length, breadth and area.
3. Read the length.
4. Read the breadth.
5. Calculate area = length × breadth.
6. Display the area.
7. Stop.

Pseudocode

START

DECLARE length, breadth, area

READ length
READ breadth

area := length * breadth

WRITE "Area = ", area

STOP
        

7. Example 3 – Area of a Circle

Problem: Calculate and display the area of a circle for a given radius.

For beginner-level calculations, we can use π = 3.14.

Algorithm

1. Start.
2. Declare radius and area.
3. Read the radius.
4. Calculate area = 3.14 × radius × radius.
5. Display the area.
6. Stop.

Pseudocode

START

DECLARE radius, area

READ radius

area := 3.14 * radius * radius

WRITE "Area of circle = ", area

STOP
        

8. Example 4 – Average of Three Numbers

Problem: Calculate and display the average of three numbers.

Algorithm

1. Start.
2. Declare a, b, c and avg.
3. Read the three numbers.
4. Calculate the average.
5. Display the average.
6. Stop.

Pseudocode

START

DECLARE a, b, c, avg

READ a
READ b
READ c

avg := (a + b + c) / 3

WRITE "Average = ", avg

STOP
        

9. Example 5 – Simple Interest

Problem: Calculate Simple Interest using principal, rate of interest and duration.

Where:

• P = Principal amount
• R = Rate of interest
• N = Duration / Number of years
• SI = Simple Interest

Algorithm

1. Start.
2. Declare p, r, n and si.
3. Read the principal amount.
4. Read the rate of interest.
5. Read the duration.
6. Calculate si = (p × r × n) / 100.
7. Display the simple interest.
8. Stop.

Pseudocode

START

DECLARE p, r, n, si

READ p
READ r
READ n

si := (p * r * n) / 100

WRITE "Simple Interest = ", si

STOP
        

10. Flowchart

Common Flowchart Symbols

Simple Flow of a Program

11. How to Build Programming Logic

When you receive a programming problem, do not immediately start writing code. First break the problem into smaller steps.

Recommended Process

1. Understand the problem
   Identify exactly what the problem is asking.
2. Identify inputs
   Determine what information the user must provide.
3. Identify processing
   Determine what calculations or decisions are required.
4. Identify outputs
   Determine what the program must display.
5. Write the algorithm
   Express the solution step by step.
6. Write pseudocode
   Convert the algorithm into programming-like instructions.
7. Write the actual program
   Convert the pseudocode into C, Java, Python, etc.
8. Test the solution
   Try different input values and verify the output.

12. Practice Questions

Level 1 – Basic Understanding

Level 2 – Write Algorithms

Level 3 – Write Pseudocode

Level 4 – Logic Building

Level 5 – Flowchart Practice

13. Challenge Problems

14. Quick Revision