test1.c

#include <stdio.h>

typedef struct pair_struct {
    unsigned short a;
    unsigned short b;
} pair;

unsigned int swap( unsigned int );
pair procedure( pair, unsigned short );
void show_pair( pair );

pair procedure( X, c )
    pair X;
    unsigned short c;
{
    pair Y;
    Y.a = X.b ^ c;
    Y.b = swap( X.a + c );
    return Y;
}

unsigned int swap( a )
    unsigned int a;
{
    return ( ( a & 0xff00 ) >> 8 ) | ( ( a & 0x00ff ) << 8 );
}

void show_pair( X )
    pair X;
{
    printf( "[%04x:%04x]\n", X.a, X.b );
}

void show_pair_dec( X )
    pair X;
{
    printf( "[%d:%d]\n", (int) X.a, (int) X.b );
}

int main(){
    pair X = { .a = 0, .b = 0 };

    show_pair( X );
    X = procedure( X, 9402 );

    show_pair( X );
    X = procedure( X, 3453 );

    show_pair( X );
    X = procedure( X, 1324 );

    show_pair( X );

}