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C Control Statements Tutorial: if, Loops & Switch Guide

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Learn C control statements with examples. Master if, if-else, nested if, switch, while, do-while, for, break, continue, goto, and practice programs.

Module 4: Control Statements in C

Learning Objectives

By the end of this module, you will be able to:

• Understand what control statements are and why they are important.
• Make decisions using if, if-else, and nested if.
• Select multiple options using the switch statement.
• Repeat tasks using while, do-while, and for loops.
• Control loop execution using break and continue.
• Learn the basics of the goto statement and when to avoid it.
• Build beginner projects using control statements.

Introduction

Control statements determine the flow of execution in a C program. By default, a program executes statements one after another from top to bottom. However, many real-world applications require making decisions, repeating tasks, or jumping to different parts of the code.

For example:

• Check whether a student passed or failed.
• Print numbers from 1 to 100.
• Display a menu and perform the selected operation.
• Exit a loop when a condition is met.

Control statements make programs dynamic, interactive, and intelligent.

Types of Control Statements

C provides three main categories of control statements:

1. Decision-Making Statements

   • if
   • if-else
   • nested if
   • switch

2. Looping Statements

   • while
   • do-while
   • for

3. Jump Statements

   • break
   • continue
   • goto

The if Statement

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

Syntax

cCopy
1if (condition)
2{
3    // Code to execute
4}

Flow

textCopy
1Condition
2   |
3True ----> Execute Block
4   |
5False ---> Skip Block

Example

cCopy
1#include <stdio.h>
2
3int main()
4{
5    int age = 20;
6
7    if (age >= 18)
8    {
9        printf("You are eligible to vote.");
10    }
11
12    return 0;
13}

Output

textCopy
1You are eligible to vote.

The if-else Statement

The if-else statement chooses between two blocks of code.

Syntax

cCopy
1if (condition)
2{
3    // True block
4}
5else
6{
7    // False block
8}

Example

cCopy
1#include <stdio.h>
2
3int main()
4{
5    int marks;
6
7    printf("Enter marks: ");
8    scanf("%d", &marks);
9
10    if (marks >= 40)
11        printf("Pass");
12    else
13        printf("Fail");
14
15    return 0;
16}

Output

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1Enter marks: 35
2Fail

The else if Ladder

Use an else if ladder when checking multiple conditions.

Example

cCopy
1#include <stdio.h>
2
3int main()
4{
5    int marks;
6
7    printf("Enter marks: ");
8    scanf("%d", &marks);
9
10    if (marks >= 90)
11        printf("Grade A");
12    else if (marks >= 75)
13        printf("Grade B");
14    else if (marks >= 60)
15        printf("Grade C");
16    else
17        printf("Grade D");
18
19    return 0;
20}

Nested if

A nested if is an if statement placed inside another if.

Syntax

cCopy
1if (condition1)
2{
3    if (condition2)
4    {
5        // Code
6    }
7}

Example

cCopy
1#include <stdio.h>
2
3int main()
4{
5    int age = 22;
6    int citizen = 1;
7
8    if (age >= 18)
9    {
10        if (citizen == 1)
11        {
12            printf("Eligible to vote.");
13        }
14    }
15
16    return 0;
17}

The switch Statement

The switch statement selects one block of code from multiple choices.

It is often cleaner than using many else if statements.

Syntax

cCopy
1switch(expression)
2{
3    case value1:
4        // Code
5        break;
6
7    case value2:
8        // Code
9        break;
10
11    default:
12        // Code
13}

Example

cCopy
1#include <stdio.h>
2
3int main()
4{
5    int day;
6
7    printf("Enter day number (1-7): ");
8    scanf("%d", &day);
9
10    switch(day)
11    {
12        case 1:
13            printf("Monday");
14            break;
15
16        case 2:
17            printf("Tuesday");
18            break;
19
20        case 3:
21            printf("Wednesday");
22            break;
23
24        case 4:
25            printf("Thursday");
26            break;
27
28        case 5:
29            printf("Friday");
30            break;
31
32        case 6:
33            printf("Saturday");
34            break;
35
36        case 7:
37            printf("Sunday");
38            break;
39
40        default:
41            printf("Invalid day.");
42    }
43
44    return 0;
45}

Why break is Important in switch

Without break, execution continues into the next case. This behavior is called fall-through.

Example:

cCopy
1switch(choice)
2{
3    case 1:
4        printf("One");
5    case 2:
6        printf("Two");
7}

If choice is 1, both "One" and "Two" are printed.

The while Loop

A while loop repeats a block of code while a condition remains true.

Syntax

cCopy
1while(condition)
2{
3    // Code
4}

Flow

textCopy
1Condition
2   |
3True
4   |
5Execute Block
6   |
7Repeat

Example

cCopy
1#include <stdio.h>
2
3int main()
4{
5    int i = 1;
6
7    while(i <= 5)
8    {
9        printf("%d\n", i);
10        i++;
11    }
12
13    return 0;
14}

Output

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11
22
33
44
55

The do-while Loop

A do-while loop executes the code at least once, even if the condition is false.

Syntax

cCopy
1do
2{
3    // Code
4}
5while(condition);

Example

cCopy
1#include <stdio.h>
2
3int main()
4{
5    int i = 1;
6
7    do
8    {
9        printf("%d\n", i);
10        i++;
11    }
12    while(i <= 5);
13
14    return 0;
15}

Difference Between while and do-while

The for Loop

The for loop is ideal when the number of iterations is known.

Syntax

cCopy
1for(initialization; condition; update)
2{
3    // Code
4}

Example

cCopy
1#include <stdio.h>
2
3int main()
4{
5    for(int i = 1; i <= 10; i++)
6    {
7        printf("%d\n", i);
8    }
9
10    return 0;
11}

Infinite Loop

cCopy
1for(;;)
2{
3    printf("Hello");
4}

Be careful—this loop never ends unless interrupted.

The break Statement

The break statement immediately exits a loop or switch statement.

Example

cCopy
1#include <stdio.h>
2
3int main()
4{
5    for(int i = 1; i <= 10; i++)
6    {
7        if(i == 6)
8            break;
9
10        printf("%d ", i);
11    }
12
13    return 0;
14}

Output

textCopy
11 2 3 4 5

The continue Statement

The continue statement skips the current iteration and moves to the next iteration.

Example

cCopy
1#include <stdio.h>
2
3int main()
4{
5    for(int i = 1; i <= 5; i++)
6    {
7        if(i == 3)
8            continue;
9
10        printf("%d ", i);
11    }
12
13    return 0;
14}

Output

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11 2 4 5

The goto Statement (Basics)

The goto statement transfers control to a labeled statement.

Although supported in C, it should be used sparingly because it can make code difficult to read and maintain.

Syntax

cCopy
1goto label;
2
3/* Other statements */
4
5label:
6    // Code

Example

cCopy
1#include <stdio.h>
2
3int main()
4{
5    printf("Start\n");
6
7    goto end;
8
9    printf("This line will not execute.\n");
10
11end:
12    printf("End\n");
13
14    return 0;
15}

Output

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1Start
2End

When to Use goto

• Exiting deeply nested loops (rare cases)
• Error handling in low-level system programming

When to Avoid goto

• General application development
• Replacing loops or conditional statements
• Creating unstructured "spaghetti code"

Practice Project 1: Number Guessing Game

cCopy
1#include <stdio.h>
2
3int main()
4{
5    int secret = 25;
6    int guess;
7
8    printf("Guess a number between 1 and 50: ");
9    scanf("%d", &guess);
10
11    if(guess == secret)
12        printf("Congratulations! You guessed correctly.");
13    else if(guess < secret)
14        printf("Too low!");
15    else
16        printf("Too high!");
17
18    return 0;
19}

Practice Project 2: Multiplication Table

cCopy
1#include <stdio.h>
2
3int main()
4{
5    int number;
6
7    printf("Enter a number: ");
8    scanf("%d", &number);
9
10    for(int i = 1; i <= 10; i++)
11    {
12        printf("%d x %d = %d\n", number, i, number * i);
13    }
14
15    return 0;
16}

Practice Project 3: Pattern Printing

Right-Angled Triangle

cCopy
1#include <stdio.h>
2
3int main()
4{
5    int rows;
6
7    printf("Enter number of rows: ");
8    scanf("%d", &rows);
9
10    for(int i = 1; i <= rows; i++)
11    {
12        for(int j = 1; j <= i; j++)
13        {
14            printf("* ");
15        }
16
17        printf("\n");
18    }
19
20    return 0;
21}

Output

textCopy
1*
2* *
3* * *
4* * * *
5* * * * *

Common Mistakes to Avoid

• Forgetting braces {} around multiple statements in if or loops.
• Omitting the break statement in a switch, causing unintended fall-through.
• Creating infinite loops by not updating the loop variable.
• Using = instead of == in conditions.
• Overusing goto instead of structured control statements.
• Forgetting the semicolon after while(condition); in a do-while loop.

Best Practices

• Use if-else for simple decisions and switch for multiple fixed options.
• Prefer for loops when the number of iterations is known.
• Use while loops when the number of iterations depends on a condition.
• Keep loop bodies simple and readable.
• Use break and continue only when they improve code clarity.
• Avoid goto in most applications and favor structured programming.

Module Summary

In this module, you learned:

• How to make decisions using if, if-else, else if, and nested if.
• How to select from multiple options using the switch statement.
• How to repeat tasks using while, do-while, and for loops.
• How to control loop execution with break and continue.
• The basics of the goto statement and why it should be used cautiously.
• How to apply these concepts by building a number guessing game, a multiplication table generator, and a pattern printing program.

After completing this module, you'll be ready to learn functions in C, including function declaration, definition, parameters, return values, recursion, scope, and storage classes, allowing you to write modular and reusable programs.