🟡 Control Flow · Lesson 16

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 value against several case labels and runs the matching one, offering a cleaner alternative to a long chain of if-else statements when checking one variable against fixed values.

Q: Why is break used in a switch statement?

break ends the switch once a matching case has run. Without it, execution "falls through" and keeps running the cases below 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 acts like the else of a switch, letting you handle unexpected values. It is optional but usually good practice to include.

Q: Can switch be used with strings in C++?

No. A C++ switch works only with integer types and characters (a char is an integer underneath) and enum values. It cannot switch on std::string or floating-point numbers — for those you use an if-else chain instead.

Q: When should I use switch instead of if-else in C++?

Use switch when you are comparing one variable against many fixed, constant values, such as a menu choice or a day number — it is clearer and often faster. Use if-else when conditions involve ranges, multiple variables or complex expressions.

What is switch?

When you need to compare one variable against many fixed values, a long if-else chain gets hard to read. The switch statement is a cleaner way: it jumps straight to the matching case.

Basic syntax

C++

switch (value) {
    case 1:
        // runs if value == 1
        break;
    case 2:
        // runs if value == 2
        break;
    default:
        // runs if nothing matched
}

A working example

C++

#include <iostream>
using namespace std;
int main() {
    int day = 3;
    switch (day) {
        case 1: cout << "Monday\n";    break;
        case 2: cout << "Tuesday\n";   break;
        case 3: cout << "Wednesday\n"; break;
        default: cout << "Other day\n";
    }
    return 0;
}

Output:
Wednesday

Why break matters

Each case should usually end with break. If you forget it, C++ keeps running into the next cases — a bug called "fall-through." Watch what happens without breaks:

C++

int x = 1;
switch (x) {
    case 1: cout << "one ";
    case 2: cout << "two ";
    case 3: cout << "three ";
}

Output:
one two three

Because there are no breaks, matching case 1 runs everything after it too.

Deliberate fall-through

Sometimes fall-through is useful — letting several cases share one block:

C++

char c = 'e';
switch (c) {
    case 'a':
    case 'e':
    case 'i':
    case 'o':
    case 'u':
        cout << "Vowel\n";
        break;
    default:
        cout << "Consonant\n";
}

Output:
Vowel

switch vs if-else

Use switch when	Use if-else when
One variable vs many fixed values	Conditions involve ranges
Values are ints, chars or enums	You compare strings or doubles
Menu choices, day numbers	Multiple variables or logic

Common mistakes

Forgetting break, causing accidental fall-through.
Trying to switch on a string or double (not allowed).
Using a variable as a case label — labels must be constants.
Leaving out default, so unexpected values are silently ignored.

🏋️ Practice

Write a simple calculator: read two numbers and an operator character (+ - * /), then use a switch on the operator to print the result. Include a default for an invalid operator.

Summary

switch picks a block by matching a value to case labels.
break ends a case; without it, execution falls through.
default handles values that match no case.
switch works with ints, chars and enums — not strings or doubles.
Prefer switch for many fixed values; if-else for ranges and complex logic.

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 value against several case labels and runs the matching one, offering a cleaner alternative to a long chain of if-else statements when checking one variable against fixed values.

Why is break used in a switch statement?

break ends the switch once a matching case has run. Without it, execution "falls through" and keeps running the cases below 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 acts like the else of a switch, letting you handle unexpected values. It is optional but usually good practice to include.

Can switch be used with strings in C++?

No. A C++ switch works only with integer types and characters (a char is an integer underneath) and enum values. It cannot switch on std::string or floating-point numbers — for those you use an if-else chain instead.

When should I use switch instead of if-else in C++?

Use switch when you are comparing one variable against many fixed, constant values, such as a menu choice or a day number — it is clearer and often faster. Use if-else when conditions involve ranges, multiple variables or complex expressions.

switch क्या है?

जब आपको एक variable की कई निश्चित values से तुलना करनी हो, लंबी if-else श्रृंखला पढ़ना कठिन हो जाता है। switch statement एक साफ़ तरीका है: यह सीधे मेल खाने वाले case पर कूद जाता है।

बुनियादी syntax

C++

switch (value) {
    case 1:
        // value == 1 hone par chalta hai
        break;
    case 2:
        // value == 2 hone par chalta hai
        break;
    default:
        // kuchh match na hone par chalta hai
}

एक चलता उदाहरण

C++

#include <iostream>
using namespace std;
int main() {
    int day = 3;
    switch (day) {
        case 1: cout << "Monday\n";    break;
        case 2: cout << "Tuesday\n";   break;
        case 3: cout << "Wednesday\n"; break;
        default: cout << "Other day\n";
    }
    return 0;
}

Output:
Wednesday

break क्यों मायने रखता है

हर case आमतौर पर break से खत्म होना चाहिए। अगर आप इसे भूलें, C++ अगले cases में चलता रहता है — एक bug जिसे "fall-through" कहते हैं। बिना breaks के देखें क्या होता है:

C++

int x = 1;
switch (x) {
    case 1: cout << "one ";
    case 2: cout << "two ";
    case 3: cout << "three ";
}

Output:
one two three

चूँकि कोई breaks नहीं हैं, मेल खाने वाला case 1 उसके बाद का सब कुछ भी चला देता है।

जानबूझकर fall-through

कभी fall-through उपयोगी होता है — कई cases को एक block साझा करने देना:

C++

char c = 'e';
switch (c) {
    case 'a':
    case 'e':
    case 'i':
    case 'o':
    case 'u':
        cout << "Vowel\n";
        break;
    default:
        cout << "Consonant\n";
}

Output:
Vowel

switch बनाम if-else

switch तब जब	if-else तब जब
एक variable बनाम कई निश्चित values	Conditions में ranges हों
Values ints, chars या enums हों	आप strings या doubles की तुलना करें
Menu choices, day numbers	कई variables या logic

आम गलतियाँ

break भूलना, आकस्मिक fall-through पैदा करना।
string या double पर switch करने की कोशिश (अनुमति नहीं)।
Variable को case label के रूप में इस्तेमाल करना — labels constants होने चाहिए।
default छोड़ देना, तो अप्रत्याशित values चुपचाप अनदेखी हो जाती हैं।

🏋️ अभ्यास

एक सरल calculator लिखें: दो numbers और एक operator character (+ - * /) पढ़ें, फिर operator पर switch से परिणाम print करें। अमान्य operator के लिए एक default शामिल करें।

सारांश

switch value को case labels से मिलाकर block चुनता है।
break case समाप्त करता है; इसके बिना execution fall through होता है।
default उन values को संभालता है जो किसी case से मेल न खाएँ।
switch ints, chars और enums के साथ काम करता है — strings या doubles नहीं।
कई निश्चित values के लिए switch पसंद करें; ranges और जटिल logic के लिए if-else।

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