#include<stdio.h>
int main(void)
{
    unsigned short a,e,f ;    // 2 bytes data type
    unsigned int temp1,temp2,temp4; // 4 bytes data type
    unsigned long temp3; // 8 bytes data type
    a=0xFFFF;
    e=((a*a)+(a*a))/(2*a); // Line 8
    //e=(((unsigned long)(a*a)+(unsigned long)(a*a)))/(unsigned int)(2*a);    

    temp1=a*a;
    temp2=a*a;
    temp3=(unsigned long)temp1+(unsigned long)temp2; // Line 14
    temp4=2*a;

    f=temp3/temp4;

    printf("%u,%u,%lu,%u,%u,%u,%u\n",temp1,temp2,temp3,temp4,e,f,a);
    return(1);
}

How do I fix the arithmetic (At Line 8 by appropriate typecasting of intermediate results) so that overflows are taken care of ? Currently it prints 65534 instead of expected 65535.

Why is the typecast necessary for Line 14 ?