Control Statements
-Decision
Making-Branching
-If Statement
-Switch Statement
-Looping
-For Loop
-While Loop
-Do ... While Loop
-Break and Continue Statements
Decision Making - Branching
-If Statement (Simple
If Statement)
-If else Statement
-Nested If
Statement
-Ladder If else
Statement
If Statement (Simple If Statement)
If statement is a basic control flow structure of C programming language.
If statement is used when a unit of code need to be executed by a condition true or false.
If the condition is true, the code in if block will execute otherwise it does nothing.
The if statement syntax is simple as follows:
Syntax:
if(condition)
{
/* unit of code to be executed */
}
Example:
if(a= =b)
{
printf("A is
equal to B");
}
|
If Else Statement
If we want to use several conditions we can use if-else-if statement. Here are common syntax of if-else-if statement:
Syntax:
if (condition)
{
Program statement 1;
}else
{
Program statement 2;
}
Example:
if (x > y)
{
printf("x is greater than y");
}
else
{
printf("x is less than y");
}
|
The if else is actually just on extension of the general format of if statement.
If the result of the condition is true, then program statement 1 is executed,
otherwise program statement 2 will be executed.
In any case either program statement 1 is executed or program statement 2 is
executed but not both
Nested If Statement
The if statement may itself contain another if statement is known as nested if
statement.
Syntax:
if (condition)
{
if(condition)
{
statement 1;
}
else
{
statement 2;
}
}else
{
statement 3;
}
|
The if statement may be nested as deeply as you need to nest it.
One block of code will only be executed if two conditions are true.
Condition 1 is tested first and than condition 2 is tested.
The second if condition is nested in the first.
The second if condition is tested only when the first condition is true else the
program flow will skip to the corresponding else statement.
The else if Ladder
When a series of many conditions have to be checked we may use the ladder else if statement which takes the following general form.
Syntax:
if (condition1)
{
Statement – 1;
}
else if (condition2)
{
Statement2;
}else if (condition3)
{
Statement3;
}
else if (condition)
{
Statement n;
}else
{
Default statement;
}
|
This construct is known as if else construct or ladder.
The conditions are evaluated from the top of the ladder to downwards.
As soon on the true condition is found, the statement associated with it is executed and the control is transferred to the statement
x (skipping the rest of the ladder. When all the condition becomes false, the final else
containing the default statement will be executed.
C Switch Statement
The switch statement allows you to select from multiple choices based on a set of fixed
values for a given expression.
Here is the common switch statement syntax:
Syntax:
switch(expression)
{
case value1:
/* execute unit of code 1 */
break;
case value2:
/* execute unit of code 2 */
break;
...
default:
/* execute default action */
break;
}
|
Switch case statement is option of if else
statement.
The value of variable is passed to
switch(variable) to compare with each case, if variable value matches the case
variable then execution of that case occurs.
If all the cases are wrong then default case is
true like the else part of if else statement.The default case is optional.
The break; statement at the end of each case is
used to break out the case.If break is not used then all the case will be
executed.
In switch statement case may only be integer or
character
Example:
#include<stdio.h>
#include<conio.h>
void main()
{
int ch;
clrscr();
printf("Insert from 1 to
3:");
scanf("%d",&ch);
switch(ch)
{
case 1:
printf("You have entered 1");
break;
case 2:
printf("You have entered 2");
break;
case 3:
printf("you have entered 3");
break;
default:
printf("Number is out of 1 to
3");
break;
}
getch();
}
|
Looping
-For Loop (Entry Controlled)
-While Loop
-Do While Loop
Looping
Loops are useful to execute certain block of
code multiple times.
Loop will execute until the particular
condition occurs.
It is useful when we want to perform repetitive
task in program.
Consider if we want to print the numbers 1 to 100 then loop is useful
Instead of printing numbers 100 times we can
execute the loop for it
For Loop
Syntax:
for(Initialize; condition;increment)
{
//block of code
}
|
There are three parts which is separated by semi-colons in control block of the for loop.
Initialization indicates the starting value of loop
Condition is to manage the loop, loop will
execute until the condition is false
Increment is used to increment the loop counter.
We can also use for loop in nested structure.
We can also use for loop in nested structure.
Here is an example of using for loop statement to print an integer five times
Example:
void main()
{
// using for loop statement
int i = 0;
for(i = 0; i<5;i++)
{
printf("%d\n",i);
}
}
And the output is
1
2 3 4 5 In above example
i=0 is initialize with value 0
condition is i<max, means loop will run till the value of i
became 5
and i++ shows the increment of 1, means i=i+1
|
While Loop
While loop executes till the expression is true.
When expression is false, execution jump out from the
while block.
In while loop test expression is checked first
then code is executed.
Loop continues till the expression becomes
false.
Syntax:
while (expression)
{
// statements
}
Example:
#include <stdio.h>
#include<conio.h>
void main()
{
// using while loop statement
int i = 1;
//Initial value to start the loop
while(i<=5)
//test condition
{
printf("%d\n",i);
i++;
//increment value
}
getch();
}
output :
1
2 3 4 5 |
Do While:
Do While loop is same as while loop but in do
while loop
Code inside the body of do is executed and
Condition is tested at the end of the block.
If condition is true code inside the do body
execute again and this process continues till the condition becomes false.
Semicolon (;) is used at the end of while(); in
do while loop
Syntax:
do
{
// statements
}while (expression);
Example:
#include <stdio.h>
#include<conio.h>
void main()
{
// using while loop statement
int i = 1;
//Initial value to start the loop
do
{
printf("%d\n",i);
i++;
//increment value
}while(i<=5); //test condition
getch();
}
And the output is
1
2 3 4 5 |
Break and Continue
Break
Break statement is used to terminate the
loop(for,while,do). We can use break with if and switch also.
Syntax:
break;
Example:
for(i=1;i<10;i++)
{
printf("%d\n",i);
if(i==5)
break;
}
output:
1
2
3
4
5
above loop will break when the value of i become 5 |
Continue
Continue statement is used to skip values inside
the loop.
Syntax:
continue:
Example:
for(i=1;i<5;i++)
{
if(i==3)
continue;
printf("%d\n",i);
}
output:
1
2
4
5
|
Nested Loops in C
C
programming language allows to use one loop inside another loop. Following
section shows few examples to illustrate the concept.
Syntax:
The syntax for a nested
for loop statement in C is as follows:
for ( init; condition; increment )
{
for ( init; condition; increment )
{
statement(s);
}
statement(s);
}
The syntax for a nested
while loop statement in C programming
language is as follows:
while(condition)
{
while(condition)
{
statement(s);
}
statement(s);
}
The syntax for a nested
do...while loop statement in C
programming language is as follows:
do
{
statement(s);
do
{
statement(s);
}while( condition );
}while( condition );
A final note on loop nesting is that you can put any type
of loop inside of any other type of loop. For example, a for loop can be inside
a while loop or vice versa.
Example:
The following program uses a nested for loop to find the
prime numbers from 2 to 100:
#include <stdio.h>
void main ()
{
/* local variable definition */
int i, j;
for(i=2; i<100; i++)
{
for(j=2; j <= (i/j); j++)
{
if(!(i%j))
{
break; // if factor found, not prime
}
if(j > (i/j))
{
printf("%d is prime\n", i);
}
}
}
}
When the
above code is compiled and executed, it produces the following result:
2 is prime
3 is prime
5 is prime
7 is prime
11 is prime
13 is prime
17 is prime
19 is prime
23 is prime
29 is prime
31 is prime
37 is prime
41 is prime
43 is prime
47 is prime
53 is prime
59 is prime
61 is prime
67 is prime
71 is prime
73 is prime
79 is prime
83 is prime
89 is prime
97 is prime
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