Lesson 5.6. Break keyword in switch..case

In the previous lesson on the switch..case, you probably noticed that each case case ends with a break statement. This statement ends the execution of the case and exits the the switch statement.

When the break is omitted, all cases are executed (even if the test is false) until :

• a break is encountered;
• or the switch is terminated.

Example

Consider the following example where the developer forgot to put the break:

switch (code) {
  case 1 : printf ("Canada");
  case 32 : printf ("Belgium");
  case 33 : printf ("France");
  case 41 : printf ("Switzerland");
  default : printf ("Unrecognized code");
}

• If code is 1, the program displays CanadaBelgiumFranceSwitzerlandUnrecognized code
• If code is 32, the program displays BelgiumFranceSwitzerlandUnrecognized code
• If code is 33, the program displays FranceSwitzerlandUnrecognized code
• If code is 41, the program displays SwitzerlandUnrecognized code
• If code is not equal to any of the cases, the program displays Unrecognized code.

Exercises

Exercise 1

Modify the code of the previous exercise so that it can convert upper and lower case characters. Be smart and use the concepts of this course.

// Character to convert
char hex = 'B';
// Result in base 10
short dec;

// Convert hex to decimal (base 10)
// MODIFY THE SWITCH..CASE 
// TO ACCEPT LOWERCASE CHARACTERS
switch (hex) {
  case '0': dec=0; break;
  case '1': dec=1; break;
  case '2': dec=2; break;
  case '3': dec=3; break;
  case '4': dec=4; break;
  case '5': dec=5; break;
  case '6': dec=6; break;
  case '7': dec=7; break;
  case '8': dec=8; break;
  case '9': dec=9; break;
  case 'A': dec=10; break;
  case 'B': dec=11; break;
  case 'C': dec=12; break;
  case 'D': dec=13; break;
  case 'E': dec=14; break;
  case 'F': dec=15; break;
  default : dec = -1;
}

// Display the conversion result
if (dec==-1) printf ("Non valid hexadecimal number\n");
else printf ("0x%c = %d in decimal\n", hex, dec);

Here is the expected display for char hex = 'f'; :

0xf = 15 in decimal

#include <stdio.h> int main(void) { // Character to convert char hex = 'B'; // Result in base 10 short dec; // Convert hex to decimal (base 10) // MODIFY THE SWITCH..CASE // TO ACCEPT LOWERCASE CHARACTERS switch (hex) { case '0': dec=0; break; case '1': dec=1; break; case '2': dec=2; break; case '3': dec=3; break; case '4': dec=4; break; case '5': dec=5; break; case '6': dec=6; break; case '7': dec=7; break; case '8': dec=8; break; case '9': dec=9; break; case 'A': dec=10; break; case 'B': dec=11; break; case 'C': dec=12; break; case 'D': dec=13; break; case 'E': dec=14; break; case 'F': dec=15; break; default : dec = -1; } // Display the conversion result if (dec==-1) printf ("Non valid hexadecimal number\n"); else printf ("0x%c = %d in decimal\n", hex, dec); return 0; }

Exercise 2

Using a switch..case, write a program that displays whether the letter variable is a consonant or a vowel. We will assume that the variable letter can only contain a lowercase letter and nothing else. The rule is as follows (according to the answer of the French Academy):

• a, e, i, o and u are vowels;
• y is a vowel and a semi-consonant;
• all other letters are consonants.

char letter = 'o';

// Displays whether the letter is a vowel or a (semi)consonant
// COMPLETE HERE

Here is the expected display for char letter = 'o';

o is a vowel

Here is the expected display for char letter = 'z';

z is a consonant

Here is the expected display for char letter = 'y';

y is a semi-consonant
y is a vowel

#include <stdio.h> int main(void) { char letter = 'o'; // Displays whether the letter is a vowel or a (semi)consonant // COMPLETE HERE return 0; }

Quiz

What does the following code display?

int x = 0;
switch (x) {
    case 0: printf ("Bonjour");
    case 1: printf ("Hola"); 
    case 2: printf ("Konnichiwa"); 
    default : printf ("Hello");
}

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What does the following code display?

int x = 0;
switch (x) {
    case 0: printf ("Bonjour");
    case 1: printf ("Hola"); break;
    case 2: printf ("Konnichiwa"); 
    default : printf ("Hello");
}

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Which statements are true?

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See also

• Learn C programming
• Lesson 1.1. History of C programming language
• Lesson 1.2. First program
• Lesson 1.3. Compilation
• Lesson 1.4. Preprocessor directives
• Lesson 1.5. Which compiler to choose?
• Lesson 1.6. Flowchart
• Lesson 2.1. Types and variables
• Lesson 2.2. Integers
• Lesson 2.3. Floating point numbers
• Lesson 2.4. Characters
• Lesson 2.5. Variables initialization
• Lesson 2.6. Ariane flight 501
• Lesson 3.1. Arithmetic operators
• Lesson 3.2. modulo
• Lesson 3.3. Operators and types
• Lesson 3.4. Type casting
• Lesson 3.5. Bitwise operators
• Lesson 3.6. Bitwise operators details
• Lesson 3.7. Shifting operators
• Lesson 3.8. Assignment operators
• Lesson 3.9. Increment and decrement operators
• Lesson 3.10. Comparison operators
• Lesson 3.11. Logical operators
• Lesson 3.12. Operator precedence
• Lesson 4.1. printf
• Lesson 4.2. scanf
• Lesson 4.3. putchar
• Lesson 5.1. Conditional branching (if...else)
• Lesson 5.2. Nested if and indentation
• Lesson 5.3. Checking intervals
• Lesson 5.4. Ternary Operator ?:
• Lesson 5.5. switch..case statement
• Lesson 6.1. do..while loop in C
• Lesson 6.2. While loop in C
• Lesson 6.3. For loop in C
• Lesson 6.4. How to choose the right loop in C ?
• Lesson 6.5. Exercices on loops in C
• Lesson 7.1. Bit masking
• Lesson 7.2. Bit masking, how to clear a bit in C?
• Lesson 7.3. Bit masking, how to set a bit in C?
• Lesson 7.4. Bit masking, how to toggle a bit in C?
• Lesson 7.5. Bit masking, how to check a single bit in C?
• Lesson 7.6. Overview of bit masking
• Lesson 8.1. Basic syntax of C functions
• Lesson 8.2. Calling C functions
• Lesson 8.3. Void keyword
• Lesson 8.4. Return keyword
• Lesson 8.5. Variable scope
• Lesson 8.6. Global variables
• Lesson 8.7. Static variables
• Lesson 8.8. Random numbers in C
• Lesson 8.9. Mathematical functions in C
• Lesson 9.1. Syntax of C arrays
• Lesson 9.2. Array initialization
• Lesson 9.3. Multidimensional arrays
• Lesson 9.4. How C arrays are stored in memory?
• Lesson 9.5. Arrays and functions
• Lesson 9.6. Exercises on C arrays
• Lesson 10.1. Strings in C
• Lesson 10.2. Null terminated string
• Lesson 10.3. The string.h library
• Lesson 10.4. String and functions
• Lesson 11.1. Introduction to pointers in C
• Lesson 11.2. Syntax of C pointers
• Lesson 11.3. Dynamic memory allocation
• Lesson 11.4. Incrementing pointers
• Lesson 11.5. Pointers as function argument in C
• Lesson 12.1. Introduction to structures in C
• Lesson 12.2. Properties of structures in C
• Lesson 12.3. Structures and pointers
• Lesson 12.4. Structures and functions
• Lesson 13.1. Recursive functions in C
• Lesson 13.2. Depth of recursive functions
• Lesson 13.2. Mutual recursion
• Lesson 14.1. Additional exercises

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