[Dev-C++] Passig by Reference Question

[<and...@su...>]

Dear Sirs (and Ladies, if you are here),

   Please, consider the three simple codes as follows:

##############################
Program 1:
1 -#include <stdio.h>
2 -#include <stdlib.h>
3 -
4 -int sum(int, int);
5 -
6 -int main()
7 -{
8 -   int a, b, c;
9 -
10-   printf("Two Numbers Sum\n");
11-   printf("Enter First Number-->");
12-   scanf("%d", &a);
13-   printf("Enter Second Number-->");
14-   scanf("%d", &b);
15-   c = sum(a,b);
16-   printf("Sum of %d with %d is %d\n", a, b, c);
17-   system("PAUSE");
18-   return 0;
19-}
20-
21-int sum(int op1, int op2)
22-{
23-   int res;
24-
25-   res = op1 + op2;
26-   return(res);
27-}
##############################
Program 2:
1 -#include <stdio.h>
2 -#include <stdlib.h>
3 -
4 -void sum(int, int, int *);
5 -
6 -int main()
7 -{
8 -   int a, b, c;
9 -
10-   printf("Two Numbers Sum\n");
11-   printf("Enter First Number-->");
12-   scanf("%d", &a);
13-   printf("Enter Second Number-->");
14-   scanf("%d", &b);
15-   sum(a, b, &c);
16-   printf("The Sum of %d with %d is %d\n", a, b, c);
17-   system("PAUSE");
18-   return 0;
19-}
20-
21-void sum(int op1, int op2, int *res)
22-{
23-   *res = op1 + op2;
24-
25-   return;
26-}
##############################
Program 3:
1 -#include <stdio.h>
2 -#include <stdlib.h>
3 -
4 -void sum(int, int, int *);
5 -
6 -int main()
7 -{
8 -   int a, b, *c;
9 -
10-   c=(int *) malloc(sizeof(int));
11-   printf("Two Numbers Sum\n");
12-   printf("Enter First Number-->");
13-   scanf("%d", &a);
14-   printf("Enter Second Number-->");
15-   scanf("%d", &b);
16-   sum(a, b, c);
17-   printf("The Sum of %d with %d is %d\n", a, b, *c);
18-   system("PAUSE");
19-   return 0;
20-}
21-
22-void sum(int op1, int op2, int *res)
23-{
24-   *res = op1 + op2;
25-   return;
26-}
################
Fight Between Programmers Scenario:
A-I prefer to use program 2 instead of program 3 to demonstrate the way how
to use passing
  by reference over the original passing by value program 1. I prefer it
because I find this
  kind of manipulation in the books and itsn´t necessary to change the
nature of the variables
  (c integer variable in this case- look for line 8 in P2 and line 8 in P3);
B-If we are already inside a function, and this function needs to pass a
pointer variable to
  other funcion, ok, is only use a passing way like line 16 of Program 3
(integer pointer c
  variable in this case).
################
My Question:
Q1-Are both Programs, 2 and 3, correct? Please comment.
Q2-Any opposition about my opinion in "A" Scenario?
Q3-Any opposition about my opinion in "B" Scenario?
Q4-Any additional comments?

Regards
Andre