The addition of two numbers in C language is performing the arithmetic operation of adding them and printing their sum on the screen. For example, if the input is 5, 6, the output will be 11.

## Addition program in C

int main()

{

int x, y, z;

printf("Enter two numbers to add\n");

scanf("%d%d", &x, &y);

z = x + y;

printf("Sum of the numbers = %d\n", z);

return 0;

}

Output of the program:

Download Add numbers program executable.

In the expression (z = x + y), overflow may occur if the sum is greater than the maximum value that the variable z can store.

Similarly, we can write a program that performs subtraction, multiplication, and division of two numbers.

## Addition without using third variable

int main()

{

int a = 1, b = 2;

/* Storing result of the addition in variable a */

a = a + b;

printf("Sum of a and b = %d\n", a);

return 0;

}

Doing this isn't recommended because the original value of the variable 'a' is lost; if we require it further in the program, then we will not have it.

## C program to add two numbers repeatedly

int main()

{

int a, b, c;

char ch;

while (1) {

printf("Input two integers\n");

scanf("%d%d", &a, &b);

getchar();

c = a + b;

printf("(%d) + (%d) = (%d)\n", a, b, c);

printf("Do you wish to add more numbers (y/n)\n");

scanf("%c", &ch);

if (ch == 'y' || ch == 'Y')

continue;

else

break;

}

return 0;

}

Output of program:

2 6

(2) + (6) = (8)

Do you wish to add more numbers (y/n)

y

Input two integers

2 -6

(2) + (-6) = (-4)

Do you wish to add more numbers (y/n)

y

Input two integers

-5 3

(-5) + (3) = (-2)

Do you wish to add more numbers (y/n)

y

Input two integers

-5 -6

(-5) + (-6) = (-11)

Do you wish to add more numbers (y/n)

n

## C program for addition of two numbers using a function

We can calculate sum of two integers using a function.

long addition(long, long);

int main()

{

long first, second, sum;

scanf("%ld%ld", &first, &second);

sum = addition(first, second);

printf("%ld\n", sum);

return 0;

}

long addition(long a, long b)

{

long result;

result = a + b;

return result;

}

We are using long data type as it can handle large numbers.

To add numbers that don't fit in in-built data types, use an array, a string, or other suitable data structure.