Control Statement
Generally C program statement is executed in a order in which they appear in the program. But sometimes we use decision making condition for execution only a part of program, that is called control statement. Control statement defined how the control is transferred from one part to the other part of the program. There are several control statement like if...else, switch, while, do....while, for loop, break, continue, goto etc.
Conditional Statement are 4 types:
- if statement
- if…..else ... Statement
- Nesting of if …else
- If….else LADDER
If Statement
Statement execute set of command like when condition is true and its syntax is
If (condition)
Statement;
The statement is executed only when condition is true. If the if statement body is consists of several statement then better to use pair of curly braces. Here in case condition is false then compiler skip the line within the if block.
void main() {
int n;
printf (“ enter a number:”);
scanf(“%d”,&n);
If (n>10)
Printf(“ number is grater”);
}
Output:
Enter a number:12
Number is greater
if…..else ... Statement
it is bidirectional conditional control statement that contains one condition & two possible action. Condition may be true or false, where non-zero value regarded as true & zero value regarded as false. If condition are satisfy true, then a single or block of statement executed otherwise another single or block of statement is executed.
Its syntax is:-
Statement1;
Statement2;
} else
{
Statement1;
Statement2;
}
Else statement cannot be used without if or no multiple else statement are allowed within one if statement. It means there must be a if statement with in an else statement.
Example:-
/* To check a number is eve or odd */
void main()
{
printf (“enter a number:”);
sacnf (“%d”, &n);
If (n%2==0)
printf (“even number”);
else
printf(“odd number”);
}
Output:
enter a number:121
odd number
Nesting of if …else
When there are another if else statement in if-block or else-block, then it is called nesting of if-else statement.
Syntax is :-
{
If (condition)
Statement1;
else
Statement2;
}
Statement3;
If….else LADDER
In this type of nesting there is an if else statement in every else part except the last part. If condition is false control pass to block where condition is again checked with its if statement.
Syntax is :-
Statement1;
else if (condition)
statement2;
else if (condition)
statement3;
else
statement4;
This process continue until there is no if statement in the last block. if one of the condition is satisfy the condition other nested “else if” would not executed.
But it has disadvantage over if else statement that, in if else statement whenever the condition is true, other condition are not checked. While in this case, all condition are checked.
Loops in C
There are three types of loops in C
- While loop
- do while loop
- for loop
While loop
Syntax:-
while(condition)
{
Statement 1;
Statement 2;
}
Or
while(test condition)
Statement;
The test condition may be any expression .when we want to do something a fixed no of times but not known about the number of iteration, in a program then while loop is used.
Here first condition is checked if, it is true body of the loop is executed else, If condition is false control will be come out of loop.
Example:-
/* wap to print 5 times welcome to C” */
#include
do while loop
for loop
int i,j;
for(i=0;i<2;i++)
for(j=0;j<5; j++)
printf(“%d %d”, i, j);
}
Output: i=0
j=0 1 2 3 4
i=1
j=0 1 2 3 4
Break statement(break)
Sometimes it becomes necessary to come out of the loop even before loop condition becomes false then break statement is used. Break statement is used inside loop and switch statements. It cause immediate exit from that loop in which it appears and it is generally written with condition. It is written with the keyword as break. When break statement is encountered loop is terminated and control is transferred to the statement, immediately after loop or situation where we want to jump out of the loop instantly without waiting to get back to conditional state.
When break is encountered inside any loop, control automatically passes to the first statement after the loop. This break statement is usually associated with if statement.
Example :
void main() {
int j=0;
for(;j<6;j++)
if(j==4)
break;
}
Output: 0 1 2 3
Continue statement (key word continue)
Continue statement is used for continuing next iteration of loop after skipping some statement of loop. When it encountered control automatically passes through the beginning of the loop. It is usually associated with the if statement. It is useful when we want to continue the program without executing any part of the program.
The difference between break and continue is, when the break encountered loop is terminated and it transfer to the next statement and when continue is encounter control come back to the beginning position.
In while and do while loop after continue statement control transfer to the test condition and then loop continue where as in, for loop after continue control transferred to the updating expression and condition is tested.
Example:-
void main() {
int n;
for(n=2; n<=9; n++)
{
if(n==4)
continue;
printf(“%d”, n);
}
Printf(“out of loop”);
}
Output: 2 3 5 6 7 8 9 out of loop
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