🟢 Beginner · Lesson 12

switch-case Statement

Q: What is a switch statement in C?

A switch statement chooses one block of code to run based on the value of a variable. It compares the variable against several case labels and runs the matching one, offering a cleaner alternative to a long chain of if-else statements.

Q: Why is break used in a switch statement?

break ends the switch after a matching case runs. Without it, execution "falls through" and keeps running the following cases too. So you normally put a break at the end of each case unless you deliberately want fall-through.

Q: What is the default case in a switch?

The default case runs when none of the other case labels match the value. It works like the else of a switch, letting you handle unexpected or leftover values. It is optional but usually good practice to include.

Q: What is the difference between switch and if-else in C?

A switch tests one variable against several constant values and is often clearer for many fixed options. if-else can test any condition, including ranges and complex expressions, so it is more flexible. Use switch for many equality checks on one value, if-else for everything else.

Q: What data types can a switch use in C?

A C switch works with integer types and characters, since a char is an integer underneath. It cannot switch on floating-point numbers or strings, and every case label must be a constant value, not a variable or range.

switch Statement Syntax

The switch statement is a multi-way decision statement. It tests a variable against a list of constant values (cases) and executes the matching block.

Syntax

switch (expression) {
    case value1:
        // code for case 1
        break;
    case value2:
        // code for case 2
        break;
    default:
        // code if no case matches
}

expression must evaluate to an integer or char (not float/double)
Case values must be constants (literals or #define values)
Each case ends with break (usually)
default is optional — runs when no case matches

How switch Works

Evaluate the switch(expression)
Compare result with each case value from top to bottom
On match → jump to that case and start executing
Execute until a break is encountered (or switch ends)
If no match → execute default (if present)

The Role of break

Without break, execution "falls through" into the next case! This is a feature (fall-through) but usually a bug for beginners.

C Language – Without break (Fall-through)

int x = 2;
switch(x) {
    case 1: printf("One\\n");
    case 2: printf("Two\\n");   // Matches here
    case 3: printf("Three\\n"); // Falls through! No break in case 2
    default: printf("Default\\n"); // Also falls through!
}

Two Three Default

⚠️ Always Use break!

Unless you intentionally want fall-through, always put break; at the end of each case. Forgetting break is a very common C bug.

The default Case

default runs when no case matches. It's optional but recommended as a safety net.

Complete Programs

Example 1: Day of Week

C Language

#include <stdio.h>
int main() {
    int day;
    printf("Enter day number (1-7): ");
    scanf("%d", &day);
    switch(day) {
        case 1: printf("Monday\\n");    break;
        case 2: printf("Tuesday\\n");   break;
        case 3: printf("Wednesday\\n"); break;
        case 4: printf("Thursday\\n");  break;
        case 5: printf("Friday\\n");    break;
        case 6: printf("Saturday\\n");  break;
        case 7: printf("Sunday\\n");    break;
        default: printf("Invalid! Enter 1-7\\n");
    }
    return 0;
}

Enter day number (1-7): 5 Friday

Example 2: Calculator using switch

C Language – Switch Calculator

#include <stdio.h>
int main() {
    float a, b;
    char op;
    printf("Enter: num op num (e.g. 5 + 3): ");
    scanf("%f %c %f", &a, &op, &b);
    switch(op) {
        case '+': printf("= %.2f\\n", a + b); break;
        case '-': printf("= %.2f\\n", a - b); break;
        case '*': printf("= %.2f\\n", a * b); break;
        case '/':
            if(b != 0) printf("= %.2f\\n", a / b);
            else printf("Division by zero!\\n");
            break;
        default: printf("Unknown operator\\n");
    }
    return 0;
}

Enter: num op num (e.g. 5 + 3): 10 * 4 = 40.00

Example 3: Vowel or Consonant (char switch)

C Language – Multiple case labels

#include <stdio.h>
int main() {
    char ch;
    printf("Enter a letter: ");
    scanf("%c", &ch);
    switch(ch) {
        case 'a': case 'e': case 'i':
        case 'o': case 'u':
        case 'A': case 'E': case 'I':
        case 'O': case 'U':
            printf("%c is a Vowel\\n", ch);
            break;
        default:
            printf("%c is a Consonant\\n", ch);
    }
    return 0;
}

Enter a letter: A A is a Vowel

switch vs if-else

Feature	switch	if-else
Condition type	Only equality (==) with integers/chars	Any condition (range, logical, etc.)
Readability	Cleaner for many discrete values	Better for complex conditions
Performance	Faster (uses jump table)	Slower for many conditions
Float/double	❌ Not allowed	✅ Allowed
Multiple values	✅ Multiple case labels	Needs OR (\|\|) operator

Summary

switch matches an expression against constant case values
Without break, execution falls through to next case
default runs when no case matches
Only works with int and char — not float, double, or strings
Multiple case labels can share one code block
Use switch when checking one variable against many discrete values

🏋️ Practice

Write: (1) Month name from number (1=January...) (2) Season from month number (3) Simple menu with 4 operations (4) Direction from WASD key input.

Frequently Asked Questions

What is a switch statement in C?

A switch statement chooses one block of code to run based on the value of a variable. It compares the variable against several case labels and runs the matching one, offering a cleaner alternative to a long chain of if-else statements.

Why is break used in a switch statement?

break ends the switch after a matching case runs. Without it, execution "falls through" and keeps running the following cases too. So you normally put a break at the end of each case unless you deliberately want fall-through.

What is the default case in a switch?

The default case runs when none of the other case labels match the value. It works like the else of a switch, letting you handle unexpected or leftover values. It is optional but usually good practice to include.

What is the difference between switch and if-else in C?

A switch tests one variable against several constant values and is often clearer for many fixed options. if-else can test any condition, including ranges and complex expressions, so it is more flexible. Use switch for many equality checks on one value, if-else for everything else.

What data types can a switch use in C?

A C switch works with integer types and characters, since a char is an integer underneath. It cannot switch on floating-point numbers or strings, and every case label must be a constant value, not a variable or range.

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