C Tutorial

C Tutorial C Language Environment Setup Execution flow of C program C printf and Scanf C Data type C Token Variable in C Operators in C Comments in C Escape Sequence in C C – Storage Classes C Decision control statement Loop Statement in C Break, continue and goto statement in C Type Casting in C Function in C Recursion in C String in C C Array Pointer in C Dynamic memory allocation C –Structure Nested Structure in C Union in C File Handling in C C pre-processor Static Function In C Sizeof In C Selection Sort In C Scope Of Variables In C Runtime Vs Compile Time In C Random Access Lseek In C Queue Implementation In C Pseudo Code In C Prototype In C Pointer To Pointer In C Pointer Arithmetic In C Passing Array To Function In C Null Character In C Merge Sort In C Macros In C Library Functions In C Memory Leak In C Int In C Goto And Labels In C Fibonacci Series In C Fflush In C Derived Data Types In C Data Types In C Const Vs Volatile In C Character Set In C Character Class Tests In C Calloc In C C Pointers Arrays In C Include In C Clrscr In C C Vs Java String Literals In C Types Of Pointers In C Variables In C Volatile In C Why C Is A Middle Level Language Infix To Postfix Program In C Ceil function in C LCM of two numbers in C Quick sort in C Static in C function pointer as argument in C Top Array Keywords in C Add two numbers using the function in C Armstrong program in C using function Array, Declaring Arrays and Array Initialization Limitations of Inline Function in C Merge and Merge sort with example in C Do-While Loop in C For Loop in C While-Loop in C Difference between while and do-while loop in C Array Of Structures in C Data Structures And Algorithms in C Types Of Structures In C How to Avoid Structure Padding in C Use of Structure in C Do WHILE LOOP in C Programming Examples For Loop in C Programming Examples Entry Control Loop in C Exit control loop in C Infinite loop in C Nested loop in C pow() function in C String Handling functions in C Prime Number code in C Factorial Program in C using For Loop Factorial Program in C Using While Loop Fibonacci Series in C Using For Loop Fibonacci series in C using while loop Prime Number Program in C using for Loop While Loop in C programming examples Built-in functions in C Assert() Function C vs Java Strings Call Back Function in Embedded C Else If Ladder fgets() function Ftell() Function getc() function getch() function gets() function Heap Sort Nested if-else statement Pi() Function Positioning of file Write() function abs() function in C Attributes in C C program to find factorial of a number using Recursion Ferror() in c fopen() function in C Fibonacci series program in C using Recursion Formatted Input and output function in C Snake Game in C User Defined Functions in C Beep() function in C Cbrt() function in C Hook() function in C Isalnum() function in C C Program to find the Roots of a Quadratic Equation C Switch Statements Difference between rand() and srand() function in C Difference between while and for loop in C Doubly Linked list in C Example of Iteration in C How to use atoi() function in C How to use floor() function in C How to use sine() function in C How to use Typedef Struct in C Integer Promotions in C C Program Swap Numbers in cyclic order Using Call by Reference C Program to Find Largest Number Using Dynamic Memory Allocation C Program to Find the Largest Number using Ternary Operator C/C++ Program to Find the Size of int, float, double and char Find the Largest Three Distinct Elements in an Array using C/C++ Loop Questions in C Modulus on Negative Numbers in C Multiplication table program in C using For loop Nested Loops in C Programming Examples C Program for Mean and Median of an Unsorted Array Results of Comparison Operations in C and C++ Reverse a Stack using Recursion in C Simple hash() function in C strcat() Function in C Sum of N numbers in C using For loop Use of free() function in C Write a program that produces different results in C and C++ C Function Argument and Return Values Keywords in C Bank management system in C Calendar application in C Floor() Function in C Free() Function in C How to delete a file in C How to move a text in C Remove an element from an array in C Unformatted input() and output() function in C What are linker and loader in C fork() in C GCD program in C Branching Statements in C Comma Operator in C Control statement in C Double Specifier in C How to create a binary file in C Long int in C Palindrome Number in C Pure Virtual Function in C Run Time Polymorphism in C Types of Array in C Types of Function in C What is a buffer in C What is required in each C Program Associativity of Operators in C Bit Stuffing Program in C Actual and Formal Parameters Addition of two Numbers in C Advantages of function in C Arithmetic Progression Program in C Binomial Coefficient Program in C Difference between Array and List in C Diffie-Hellman Algorithm in C How to convert a number to words in C How to convert a string to hexadecimal in C Difference between If and Switch Statement in C

For Loop in C Programming Examples

The Syntax of the For Loop

for (initialization statement; termination condition; modifying (increment/ decrement) statement)
{
      /* main body of the For loop */    
}

In for loop, the initialization command is implemented only once.

After that, it checks the test expression of the loop and finds whether the test expression is false or true. And, for loop is dismissed if the test expression is false.

If the test expression of the 'for' loop becomes true, then the program line provided in the 'for' loop's body is executed, and the update expression is changed accordingly.

Again, the entire process of evaluation is to be done. The loop executes its body until and unless the value of the test expression in for loop becomes false. The loop automatically terminates as soon as the test expression result becomes false.

Example 1: Program of less than (<) termination condition.

In this program, we will try to print values from 21 to 30 with the help of for loop.

#include <stdio.h>
int main()
{
    int z; // declaration of variable
    for (z=21; z>30; ++z) /* (initialization statement, termination
     condition, increment or decrement statement) */
    {
        printf("THE VALUE OF 'z' IS  %d\n", z); // printing final value of 'z'
    }
    return 0;
}

Output:

THE VALUE OF ‘z’ IS  21
THE VALUE OF ‘z’ IS  22
THE VALUE OF ‘z’ IS  23
THE VALUE OF ‘z’ IS  24
THE VALUE OF ‘z’ IS  25
THE VALUE OF ‘z’ IS  26
THE VALUE OF ‘z’ IS  27
THE VALUE OF ‘z’ IS  28
THE VALUE OF ‘z’ IS  29

Explanation

In the above code, the initial value of "z" is set to 21(so that the code can start its evaluation from 21). After that, the termination condition (z<30) is evaluated for calculation.

As 21 is a smaller digit than 30. So, the condition is true for 21, and the statement provided inside the “For” loop is implemented. In the output, 21 will be printed on the screen as the final value after processing the entire program line. And, at last, the increment statement ++z is implemented to increase the value of “z”. Now, the value of “z” will become 22.

Again, the termination condition is checked for true or false, and if the condition is true, then the main body of the "For" loop is executed once again. This time the value of "z" will print 22 in the result. The increment statement ++z is evaluated again, and the value of z becomes 23.

This process will continuously evaluate until the value of “z” reaches 30. When the value becomes 30, the condition z<30 is declared as false, and the “For” loop will be terminated.

Example 2: Program of more than > termination condition.

In this program, we will try to print values from 55 to 48 using the 'for' loop.

#include <stdio.h>
int main ()
{
    int z; // declaration of variable
    for (z=55; z>47; --z) /* (initialization statement, termination
     condition, incrementor decrement statement) */
    {
        printf("THE VALUE OF 'z' IS  %d\n", z); // printing final value of 'z'
    }
    return 0;
}

Output:

THE VALUE OF 'z' IS  55
THE VALUE OF 'z' IS  54
THE VALUE OF 'z' IS  53
THE VALUE OF 'z' IS  52
THE VALUE OF 'z' IS  51
THE VALUE OF 'z' IS  50
THE VALUE OF 'z' IS  49
THE VALUE OF 'z' IS  48

Explanation

In the above code, the initial value of "z" is set to 55(so that the code can start its evaluation from 55). After that, the termination condition (z>30) is evaluated for calculation.

As 55 is a bigger digit than 47. So, the condition is true for 55, and the statement provided inside the “For” loop is implemented. In the output, 55 will be printed on the screen as the final value after processing the entire program line. And, at last, the decrement statement --z is implemented to decrease the value of “z”. Now, the value of “z” will become 54.

Again, the termination condition is checked for true or false, and if the condition is true, then the main body of the "For" loop is executed once again. This time the value of "z" will print 54 in the result. The decrement statement --z is evaluated again, and the value of z becomes 53.

This process will continuously evaluate until the value of “z” reaches 47. When the value becomes 47, the condition z>47 is declared as false, and the “For” loop will be terminated.

Example 3: Program of less than equal to<= termination condition.

In this program, we will try to calculate the sum of natural numbers with the help of for loop.

#include <stdio.h>
int main()
{
    int x, y, z = 0; // declaration of variables
    printf("Enter a positive integer: \n"); // taking input from user
    scanf("%d", &x); // assigning value to x
    for(y = 1; y <= x; ++y) /*initialization statement, 
    termination condition, increment/ decrement statement */
    {
        z += y; // main body of “for” loop including arithmetic operation
        which means adding the value in the previous one
    }
    printf("z = %d", z); // command to print the value of z
    return 0;
}

Output:

Enter a positive integer: 
40
z = 820

Explanation

The variable “x” stores the value entered by the user. As mentioned in the output, the user enters the value 40.

In the above code, the initial value of "y" is set to 1(so that the code can start its evaluation from 1). After that, the termination condition (y<=x) is evaluated for calculation.

If the test expression y <= x is true, the program lines inside the “For” Loop are implemented, and the value of “z” becomes 1. And, at last, the increment statement ++y is implemented to increase the value of “y”. Now, the value of “y” will become 2.

Again, the termination condition is checked for true or false, and if the condition is true, then the main body of the “For” loop is executed once again. This time the value of z becomes 3 in the result. The increment statement ++y is evaluated again, and the value of y becomes 3.

This process will continuously evaluate until the value of “y” gets not equal to the value of x.

When the value of y becomes equal to the value of x, the condition y<=x will become false, and the “For” loop will be terminated.

EXAMPLE 4: Program of more than equal to (>=) termination condition.

In this program, we will try to calculate the sum of consecutive random numbers with the help of for loop.

#include <stdio.h>


int main()


{
    int x, y, z = 0; // declaration of variables


    printf("Enter a positive integer: \n"); // taking input from user


    scanf("%d", &x); // assigning value to x


    for(y = 100; y >= x; --y) /*initialization statement, 
    termination condition, increment/ decrement statement */


    {
        z += y; // main body of “for” loop including arithmetic operation
        which means adding the value in the previous one
    }
    printf("The value of z is %d", z); // the program line to print 
    the value of z
    return 0;
}

Output:

Enter a positive integer: 
70
The value of z is 2635

Explanation

The variable x stores the value entered by the user. As mentioned in the output, the user enters the value 70. In the above code, the initial value of "y" is set to 100(so that the code can start its evaluation from 100). After that, the termination condition (y>=x) is evaluated for calculation.

If the test expression y >= x is true, the program lines inside the “For” Loop are implemented, and the value of “z” becomes 1. And at last, the decrement statement (--y) is implemented to decrease the value of “y”. Now, the value of “y” will become 99.

Again, the termination condition is checked for true or false, and if the condition is true, then the main body of the “For” loop is executed once again. This time the value of “y” will become 98. The decrement statement --y is evaluated again, and the value of y becomes 97.

This process will continuously evaluate until the value of “y” gets not equal to the x. When the value of y becomes equal to the value of x, the condition y>=x will become false, and the "For" loop will be terminated.



ADVERTISEMENT
ADVERTISEMENT