New to Programming

[Traves]

Help -- I am teaching myself C through a book and one of the exercises calls for you to write a program that has a function which calls two other functions. I wrote the following code and compiled it with DevC++, Pelles C, and Quincy 99. None of them gave me any warnings or errors but the compiled program (from any of the above 3 compilers) will not run on Windows XP or Windows 98. The code is as follows:

/* This program asks whether or not you want to multipy or divide then */
/* performs the calculation */

#include <stdio.h>

char g;
int a, b, c, t, s;
int x,y,w,z;

int calculate(int x, int y );
int product(int w,int z );
int divide(int w,int z);

int main( void )
{
    printf("This program will multiply two numbers or\n");
    printf("divide the first number by the second.\n");
    printf("Press 1 if you want to multiply\n");
    printf("Press 2 if you want to divide: ");
    scanf("%d", g);
    printf("\nEnter in the first number: ");
    scanf("%d", a);
    printf("\nEnter in the second number: ");
    scanf("%d", b);
    c = calculate( a, b );
    
    if (g == 1)
    {
        printf("Their product is: %d\n", c);
    }
    else
    {
        printf("%d divided by %d is %d.\n\n", a, b, c);
    }
    
    system("PAUSE");
    return 0;
 }

int calculate( x, y )
{   
    if (g == 1)
    {
         t = product( x, y );      
    }
    else
    {    
        t = divide( x, y);
    }
    return t;
}

int product( w, z )
{
    s = ( w * z);
    return s;
}

int divide( w, z)
{
    s = ( w * z);
    return s;
}

When I run the program I encounter the error after I enter a value when prompted to enter 1 or 2.
Any help would be very welcome. And please forgive my programming ignorance.

[Robc]

>scanf("%d", g);
>scanf("%d", a);
>scanf("%d", b);
scanf expects an address, so if the object isn't a pointer you need to prefix it with &.

>system("PAUSE");
This is okay for now, but keep in mind that this use of system is not recommended for several good reasons. You also need to include <stdlib.h> because that's where system is declared.

>int calculate( x, y )
>int product( w, z )
>int divide( w, z )
You need to specify the types, just like in your prototypes.

And your divide function actually multiplies. This works:

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

char g;
int a, b, c, t, s;
int x,y,w,z;

int calculate(int x, int y );
int product(int w,int z );
int divide(int w,int z);

int main( void )
{
    printf("This program will multiply two numbers or\n");
    printf("divide the first number by the second.\n");
    printf("Press 1 if you want to multiply\n");
    printf("Press 2 if you want to divide: ");
    scanf("%d", &g);
    printf("\nEnter in the first number: ");
    scanf("%d", &a);
    printf("\nEnter in the second number: ");
    scanf("%d", &b);
    c = calculate( a, b );
    
    if (g == 1)
    {
        printf("Their product is: %d\n", c);
    }
    else
    {
        printf("%d divided by %d is %d.\n\n", a, b, c);
    }
    
    system("PAUSE");
    return 0;
 }

int calculate( int x, int y )
{   
    if (g == 1)
    {
         t = product( x, y );      
    }
    else
    {    
        t = divide( x, y);
    }
    return t;
}

int product( int w, int z )
{
    s = ( w * z);
    return s;
}

int divide( int w, int z )
{
    s = ( w / z);
    return s;
}

[Traves]

This is a correction in the code I posted:

"int divide ( w, z )" should read:

int divide ( w, z )
{
      s = ( w / z );
      return s;
}

although the original performs the wrong function at "int divide"- I still don't see why the program won't work at all past the first prompt. Thank you for your patience.

[Traves]

Thank you for the clarification!
and -- Wow that was quick!

[Traves]

I've been getting away with a lot of messy code (until now!) it sounds like.

[kermit]

Originally posted by Traves

char g;
int a, b, c, t, s;
int x,y,w,z;

int calculate(int x, int y );
int product(int w,int z );
int divide(int w,int z);

int main( void )
{
    printf("This program will multiply two numbers or\n");
    printf("divide the first number by the second.\n");
    printf("Press 1 if you want to multiply\n");
    printf("Press 2 if you want to divide: ");
    scanf("%d", g);
    printf("\nEnter in the first number: ");
    scanf("%d", a);
    printf("\nEnter in the second number: ");
    scanf("%d", b);
    c = calculate( a, b );

You might want to change your scanf() format specifier from %d to %c to reflect the fact that the variable g is a char as opposed to an int.

edit:: Actually, you want to change the variable g to an int - if its a char and you press 1 to select multiply, then you are putting the ascii value of one into g, which is 49 I believe - not what you want. Either way, you want your scanf() format specifiers to match the type of variable you are looking to store the data in.

edit::

One other thing I forgot to add - this is not something that is wrong, but it is another way to do things. Your code first, then my modification:

int divide ( w, z )
{
      s = ( w / z );
      return s;
}

You could do this instead:

int divide ( w, z )
{
      return ( w / z );
}

A little simpler I think.

~/

[Robc]

>You might want to change your scanf() format specifier from %d to %c to reflect the fact that the variable g is a char as opposed to an int.
That would break the program though. The conditional test is for 1, not '1'.

[kermit]

One step ahead of you. Well, maybe half a step.

[Emmanuel Delaha]

I wrote the following code and compiled it with DevC++, Pelles C, and Quincy 99. None of them gave me any warnings or errors

You are kidding, aren't you ?

Compilateur: Default compiler
Building Makefile: "D:\Dev-Cpp\Makefile.win"
Exécution de  make...
make.exe -f "D:\Dev-Cpp\Makefile.win" all
gcc.exe -D__DEBUG__ -c main.c -o main.o -I"C:/DEV-CPP/include" -W -Wall -O2   -g3

main.c: In function `main':
main.c:20: warning: format argument is not a pointer (arg 2)
main.c:22: warning: format argument is not a pointer (arg 2)
main.c:24: warning: format argument is not a pointer (arg 2)

main.c:36: warning: implicit declaration of function `system'

main.c: In function `calculate':
main.c:41: warning: type of `x' defaults to `int'
main.c:41: warning: type of `y' defaults to `int'

main.c: In function `product':

main.c:54: warning: type of `w' defaults to `int'
main.c:54: warning: type of `z' defaults to `int'

main.c: In function `divide':
main.c:60: warning: type of `w' defaults to `int'
main.c:60: warning: type of `z' defaults to `int'

gcc.exe -D__DEBUG__ main.o  -o "Projet1.exe" -L"C:/DEV-CPP/lib" C:/Dev-Cpp/lib/libws2_32.a -g3 

Exécution terminée
Compilation OK

Of course, you must learn how to configure your compiler correctly.