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What will be the output of the program?

 #include
 #define SWAP(a, b) int t; t=a, a=b, b=t; 
int main()
{   
    int a=10, b=12;  
    SWAP(a, b);   
    printf("a = %d, b = %d\n", a, b);     
    return 0; 
}

a = 10, b = 12

a = 12, b = 10

Error: Declaration not allowed in macro

Error: Undefined symbol 't'

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Answer : Option B

Explanation :

The macro SWAP(a, b) int t; t=a, a=b, b=t; swaps the value of the given two variable.

Step 1: int a=10, b=12; The variable a and b are declared as an integer type and initialized to 10, 12 respectively.

Step 2: SWAP(a, b);. Here the macro is substituted and it swaps the value to variable a and b.