C – Decision Making Branching Looping

switch(expression)
{
    case constant-expression  :
    statement(s);
    break; /* optional */
    
    case constant-expression  :
    statement(s);
    break; /* optional */

    /* you can have any number of case statements */

    default : /* Optional */

    statement(s);
}

switch(ch1)
{
    case 'A':
    printf("This A is part of outer switch" );
    switch(ch2)
    {   
        case 'A':
        printf("This A is part of inner switch" );
        break;

        case 'B': /* case code */
        break;
    }
    case 'B': /* case code */
    break;
}

Looping control statements (Three types)

While Loop

• Syntax: while(condition) //The condition may be any expression, and true is any nonzero
• value. The loop iterates while the condition is true.

{
    statement(s); //statement(s) may be a single statement or a block of statements.
}

Do..while Loop

Syntax :

do
{
     statement(s);
}while(condition);

Rules: the condition is true while statement break the do loops

nested while loops

Syntax :

while(condition)
{
   while(condition)
   {
       statement(s);
   }
   statement(s);
}

for Loop

Syntax :

for( init; condition; increment )     //
{
      statement(s);
}

Rules:

1. init – The init step is executed first, and only once. This step allows you to declare and initialize any loop control variables. You are not required to put a statement here, as long as a semicolon appears.
2. condition – Next, the condition is evaluated. If it is true, the body of the loop is executed.If it is false, the body of the loop does not execute and the flow of control jumps to the next statement just after the ‘for’ loop.
3. increment – After the body of the ‘for’ loop executes, the flow of control jumps back up to the increment statement. This statement allows you to update any loop control variables. This statement can be left blank, as long as a semicolon appears after the condition.

nested for loops

Syntax :

for ( init; condition; increment )
{
    for ( init; condition; increment ) 
    {
         statement(s);
    }
    statement(s);
}

Infinite Loop

A loop running continuously for an indefinite number of times is called an infinite loop.

example:

int main()
{
    for(;;)
    {
         //code to be executed
         printf("This loop will run forever.\n"); 
    }
    return 0;
}

While Loop in Infinite

while(1)
{
    //code to be executed
}

Infinite Do-While Loop:

do
{
   //code to be executed
}while(1);

Infinite For Loop:

Syntax:

for(;;)
{
	printf("ArunEwrold\t");
}

Example code:

#include<stdio.h>
int main()
{
   int n;
   for(n = 7; n!=0; n--)
     printf("n = %d", n--);
   getchar();
   return 0;
}

Output: Above C program goes in an infinite loop because n is never zero when loop condition (n != 0) is checked

break

Break can appear only within the looping control and switch statement. The purpose of the break is to bring the control out of the used blocks.

Syntax : break;

if you use break statement in unwanted place then error will be generated.

#include <stdio.h>
int a =1;

int main()
{
if(a==1)
{
// printf() displays the string inside quotation
printf(“Hello, World!”);
break;
}
return 0;
}

/****************** Result & Error *********************/
//Error : #13 a break statement may only be used within a loop or switch

continue

• Syntax : continue;

Goto Statement

Excersize

JCOKE = 3
JCOKE = JCOKE + 1
GO TO (5, 8, 9, 11, 15, 16 18, 20) JCOKE.

After the execution of the above statement, the control is transferred to statement number
A. 8
B. 11
C. 16
D. 20

• Answer: Option B (Explanation: It is a computed GO TO statement. Since J COKE = 3 + 1 = 4, the control is transferred to statement 11).

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