Loops Basics

LOOPS :


WHY DO WE NEED LOOPS ???

There may be a situation, when you need to
execute a block of code several number of times.
 In general statements are executed sequentially:
The first statement in a function is executed first,
followed by the second, and so on.
 A loop statement allows us to execute a statement
or group of statements multiple times


LOOPS :


TYPES OF LOOPS :

WHILE LOOP
 FOR LOOP
 DO-WHILE LOOP
 NESTED LOOP




LETS HAVE A CLOSER LOOK

LOOPS => WHILE LOOP
A while loop statement repeatedly executes a target
statement as long as a given condition is true.
Syntax:
The syntax of a while loop in C is:

while(condition)
{
statement(s);
}

LOOPS => WHILE LOOP


Here, statement(s) may be a single statement or a
block of statements. The condition may be any
expression, and true is any non-zero value. The
loop iterates while the condition is true.



When the condition becomes false, program control
passes to the line immediately following the loop

LOOPS => WHILE LOOP
FLOW DAIGRAM

LOOPS => WHILE LOOP
EXAMPLE :
#include<stdlib.h>
int main ()
{
// Local variable declaration:
int a = 10;
// while loop execution
while( a < 20 )
{
printf(“value of a:%d /n”, a);
a++;
}
getch()
}


LOOPS => WHILE LOOP


When the above code is compiled and executed, it
produces the following result:
value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 15
value of a: 16
value of a: 17
value of a: 18
value of a: 19

LOOPS :
FOR LOOP:
A for loop is a repetition control structure that allows
you to efficiently write a loop that needs to execute
a specific number of times.
Syntax:
The syntax of a for loop in C is:
for ( init; condition; increment )
{
statement(s);
}

LOOPS => FOR LOOP


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.



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 flow of control
jumps to the next statement just after the for loop.

LOOPS => FOR LOOP
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.
 The condition is now evaluated again. If it is
true, the loop executes and the process repeats
itself (body of loop, then increment step, and then
again condition). After the condition becomes
false, the for loop terminates.


LOOPS=> FOR LOOP


Flow Diagram:

LOOPS => FOR LOOP
Example:
#include<stdlib.h>
int main ()
{ // for loop execution
for( int a = 10; a < 20; a = a + 1 )
{
printf("value of a: %d /n”, a);
}
getch();
}

LOOPS => FOR LOOP


value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 15
value of a: 16
value of a: 17
value of a: 18
value of a: 19

LOOPS :


DO-WHILE LOOP:



Unlike for and while loops, which test the loop
condition at the top of the loop, the do...while loop
checks its condition at the bottom of the loop.



A do...while loop is similar to a while loop, except
that a do...while loop is guaranteed to execute at
least one time.

LOOPS => DO-WHILE LOOP
Syntax:
The syntax of a do...while loop in C is:
do
{
statement(s);
}
while( condition );

Notice that the conditional expression appears at
the end of the loop, so the statement(s) in the loop
execute once before the condition is tested.



Flow Diagram:



Example:

#include<stdlib.h>
int main ()
{ // Local variable declaration:
int a = 10;
// do loop execution
do
{
printf( "value of a: %dn “ ,a);
a = a + 1;
} while( a < 20 );
getch();
}



value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 15
value of a: 16
value of a: 17
value of a: 18
value of a: 19

LOOPS :


NESTED LOOPS :



A loop can be nested inside of another loop.



Syntax:
The syntax for a nested for loop statement in C is as follows:
{
{
statement(s);
}
statement(s);
// you can put more statements.
}

LOOPS => NESTED LOOP


EXAMPLE :

#include<stdlib.h>
int main ()
{
int a=1,b;
while(a<=3)
{
for(b=1;b<=3;b++)
{
printf("a = %d , b = %dn",a,b);
}
printf("n");
a++;
}
system("pause");
}

LOOPS => NESTED LOOP


a=1,b=1
a=1,b=2
a=1,b=3
a=2,b=1
a=2,b=2
a=2,b=3

a=3,b=1
a=3,b=2
a=3,b=3

Loops Basics

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