Decision Making in Programming

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Decision-making in programming allows a program to execute specific blocks of code based on certain conditions. It introduces logic into the program and makes it dynamic by enabling choices.

In C, decision-making constructs evaluate conditions (expressions that return true or false) and decide which part of the program to execute.

Types of Decision-Making Statements in C

  1. if Statement
  2. if-else Statement
  3. else if Ladder
  4. Nested if Statements
  5. switch Statement

1. if Statement

The if statement executes a block of code only if a specified condition is true.

Syntax:

if (condition)
{
// Code to execute if condition is true
}
Example

#include <stdio.h>

int main() {
int num = 10;

if (num > 5) {
printf(“Number is greater than 5.\n”);
}

return 0;
}

Output:

Number is greater than 5.

2. if-else Statement

The if-else statement provides an alternative block of code to execute when the condition is false.

Syntax:

if (condition)
{
// Code to execute if condition is true
}
else
{
// Code to execute if condition is false
}

Example:

#include <stdio.h>

int main() {
int num = 3;

if (num > 5) {
printf(“Number is greater than 5.\n”);
} else {
printf(“Number is not greater than 5.\n”);
}

return 0;
}

Output:

Number is not greater than 5.

3. else if Ladder

The else if ladder is used to check multiple conditions sequentially.

Syntax:

if (condition1)
{
// Code to execute if condition1 is true
}
else if (condition2)
{
// Code to execute if condition2 is true
}
else
{
// Code to execute if none of the above conditions are true
}

Example:

#include <stdio.h>

int main() {
int num = 0;

if (num > 0) {
printf(“Positive number.\n”);
} else if (num < 0) {
printf(“Negative number.\n”);
} else {
printf(“Zero.\n”);
}

return 0;
}

Output:

Zero.

4. Nested if Statement

An if statement can be nested inside another if or else block for more complex decision-making.

Syntax:

if (condition1)
{
if (condition2)
{
// Code to execute if both conditions are true
}
}

Example:

#include <stdio.h>

int main() {
int num = 7;

if (num > 0) {
if (num % 2 == 0) {
printf(“Positive even number.\n”);
} else {
printf(“Positive odd number.\n”);
}
}

return 0;
}

Output:

Positive odd number.

5. switch Statement

The switch statement selects one of many blocks of code to execute based on the value of a variable or expression.

Syntax:

switch (expression)
{
case value1:
// Code for value1
break;
case value2:
// Code for value2
break;
default:
// Code if no cases match
}

Example:

#include <stdio.h>

int main() {
int choice = 2;

switch (choice) {
case 1:
printf(“Option 1 selected.\n”);
break;
case 2:
printf(“Option 2 selected.\n”);
break;
default:
printf(“Invalid option.\n”);
}

return 0;
}

Output:

Option 2 selected.

Key Points About Decision Making

  1. Conditions: The conditions in if, else if, and switch are usually relational (<, >, ==) or logical (&&, ||, !).
  2. Braces {}: Recommended for clarity, even if the block contains a single statement.
  3.  switch : Ideal for scenarios with multiple fixed values.
  4. if – else : Best for complex logical conditions.

Summary Table

Construct Purpose Use Case
if Executes code if the condition is true. Single condition check.
if-else Executes one block if true, another if false. Dual path decision-making.
else if Ladder Checks multiple conditions sequentially. Multiple condition checks.
Nested if Handles hierarchical conditions. Complex decision trees.
switch Selects code block based on matching cases. Fixed values for decisions.

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