error: conflicting types for function

the two most common reasons for the conflict types of error

first, mismatch of return type b/w  function prototype declaration and the function declaration

the second is a mismatch of function parameters type b/w function prototype declaration and the function declaration

let’s see an example

#include <stdio.h>
#include <stdlib.h>
 int calsum(int x, int y);//function prototype declaration
int main()
{
    int a=1,b=2,sum;
     sum=calsum(a,b); // function call
    printf("sum=%d\n",sum);
    return 0;
}
 int calsum(int x, int y) //function declaration
{
    int d;
    d=x+y;
    return(d);
}

always make sure your function prototype declaration and function declaration should match with the same number of arguments with the same type and the same return type of function