#include <stdio.h>
#include <stdlib.h>

typedef struct{
     int a;
     int b;
} St;

void Fnc1( St s )
{
    s.a += 1;
    s.b += 2;

    printf("(f1) %d %d \n", s.a, s.b );
}

void Fnc2( St *p_s )
{
    p_s->a += 1;
    p_s->b += 2;

    printf("(f2) %d %d \n", p_s->a, p_s->b );
}

int main()
{

    St s_1;

    s_1.a = 1;
    s_1.b = 2;

    printf("(1) %d %d \n", s_1.a, s_1.b );

    Fnc1( s_1 );

    printf("(2) %d %d \n", s_1.a, s_1.b );

    Fnc2( &s_1 );

    printf("(3) %d %d \n", s_1.a, s_1.b );

    return 0;
}

/*

output:

(1) 1 2
(f1) 2 4
(2) 1 2
(f2) 2 4
(3) 2 4

*/