for loop in C ?
A for loop is a control statement using which the programmer can give instructions to the computer to execute a set of statement repeatedly as long as specified condition is satisfied. It is required to specify how many times a set of statements have to be executed, it is also called counter controlled loop.
Syntax:-
for(exp1;exp2;exp3)
{
...........
...........
}
The first expression : exp 1 contains initialization statements
The second expression: exp 2 contains limit–test expression
The third expression : exp 3 contains updating expression
How for Loop Works
- Step 1:-
The initialization statement is executed only once i.e exp1. - Step 2:-
Then, the test expression is evaluated. If the test expression is evaluated to false, then the for loop gets terminated and the control comes out of the loop. - Step 3:-
the next step the condition(Test Expression i.e exp2) is checked if the test expression is evaluated to true, statements inside the body of the for loop are executed, - Step 4:-
After successful execution of statements inside the body of the loop, the update expression (i.e exp3) also called counter variable is updated. incremented or decremented, depending on the operation (++ or –). - Step 5:-
Again the test expression is evaluated.
Example with dry Run Concepts
Note:
The for loop is always used when we know initial value, final value and updating value. The updating value can be constantly
incremented or decremented.
Q.) W.A.P to print 1 to 5 using for loop.
#include<stdio.h> #include<conio.h> void main() { int i; for(i = 1; i <=5 ; i++) { printf(“%d\n”, i ); } getch(); }
Output
1
2
3
4
5
2
3
4
5
Program Explanation
- Step 1:-
We declared integer variables called i. The initialization statement is executed only once i.e i=1 - Step 2:-
Then, the test expression is evaluated. i.e i is less than or equals to 5 or not (i <=5 ) hear condition is true so statements inside the body of the for loop are executed, and it will print the value of i i.e 1 - Step 4:-
After successful execution of statements inside the body of the loop, the update expression (i.e i++) means it incremented by 1 now the value of i is 2 - Step 5:-
Again the test expression is evaluated. and repeat step 2 till the condition is false - Step 5:-
when the condition is false means the value of i will be 6 then for loop gets terminated and the control comes out of the loop.
Q.) W.A.P to print sum of 1 to n using for loop.
#include<stdio.h> #include<conio.h> void main() { int i; printf("Enter Number); scanf("%d",&n); for(i = 1; i <=n ; i++) { s=s+i; } printf(“Sum of 1 to n is:-%d\n”,s); getch(); }
Output
Enter Number:- 5
Sum of 1 to n is:- l5
Sum of 1 to n is:- l5
Program Explanation
- Step 1:-
We declared three integer variables called i,s and n. - Step 2:-
hear we initialization s=0 because we will have to sum from 1 to n so it not initialization garwage value - Step 3:-A Message will give for entering their own values for n :- Enter a Number:- 5
- Step 4:-
- Step 5:-
Then, the test expression is evaluated. i.e i is less than or equals to 5 or not (i <=5 ) hear condition is true so statements inside the body of the for loop are executed, and it will print the value of s after assign value s=i+s - Step 6:-
After successful execution of statements inside the body of the loop, the update expression (i.e i++) means it incremented by 1 now the value of i - Step 7:-
Again the test expression is evaluated. and repeat step 2 till the condition is false - Step 8:-
When the condition is false means the value of i will be 6 then for loop gets terminated and the control comes out of the loop. - Step 9:-
and print value of s i.e Sum of 1 to n is 15
Q.) W.A.P to print table of any number using for loop.
#include<stdio.h> #include<conio.h> void main() { int i,t,n; printf("Enter a Number"); scanf("%d",&n); for(i = 1; i <=10 ; i++) { t=t*n; printf(“%d\n”, t ); } getch(); }
Output
Enter a Number.
2
2
4
6
8
10
12
14
16
18
20
2
4
6
8
10
12
14
16
18
20
Program Explanation
- Step 1:-
We declared three integer variables called i,t and n. - Step 2:-A Message will give for entering their own values for n :- Enter a Number:- 2
- Step 3:-
- Step 2:-
Then, the test expression is evaluated. i.e i is less than or equals to 10 or not (i <=10 ) hear condition is true so statements inside the body of the for loop are executed, and it will print the value of t after assign value i*n - Step 4:-
After successful execution of statements inside the body of the loop, the update expression (i.e i++) means it incremented by 1 now the value of i is 2 - Step 5:-
Again the test expression is evaluated. and repeat step 2 till the condition is false - Step 5:-
when the condition is false means the value of i will be 11 then for loop gets terminated and the control comes out of the loop.
C for loop MCQ Question
Q1. Choose a right C Statement
- Loops or Repetition block executes a group of statements repeatedly.
- Loop is usually executed as long as a condition is met.
- Loops usually take advantage of Loop Counter
- All the above.
Answer:- D.
Q2. Loops in C Language are implemented using.?
- for
- while
- do while
- All the above.
Answer:- D.
Q3.The C code ‘for(;;)’ represents an infinite loop. It can be terminated by
- break
- exit
- if
- else
Answer:- a.
Q5. for is a
- keyword
- identifier
- variable
- All the above.
Answer:- a.
Q4. ++ and -- is a
- increment or decrement operator
- identifier
- variable
- All the above.
Answer:- a.
Q6.What is the output of while Program.?
int main() { int i = 0; for (i=0; i<20; i++) { switch(i) { case 0: i += 5; case 1: i += 2; case 5: i += 5; default: i += 4; break; } printf("%d ", i); } return 0; }
- 16 21
- 66 45
- 65 69
- error
Answer:- a.