Function with variables in C

Question

Maybe a stupid question, but I don't understood why my program in C works with integers, but not with float.

#include <stdio.h>

main()
{
  float a, b;
  a = 4.5;
  b = 9.6;

  printf("Result of %.2f + %.2f = %.2f", a, b, added_up(a, b));
}

/****************************************/

added_up(a,b)
{
  float c;
  printf("Value a: %.2f \n", a);
  printf("Value b: %.2f \n", b);
    c = a + b;
  return (c);
}

My output:

Value a: 0.00
Value b: 0.00
Result of 4.50 + 9.60 = 0.00

If I define the float to int the program works. What's the failure? Should I declare the function as float, but if I try I get another failure.

You never declared the return type for `added_up`. That's a legacy construct which defaults to `int`, but would ideally give an error. Similarly, you forgot to add a forward declaration for `added_up`. Again, it defaults to a return type of `int` with unknown argument types. Add complete prototypes, and forwards, for all your functions. Then try it again. — Tom Karzes, Oct 29 '22 at 12:31
Whatever resource you're using to learn C, it's severely outdated. In C since a few decenniums you *must* declare function with a return type, and *must* use actual types for variable declarations, and *must* declare functions before you call them. — Some programmer dude, Oct 29 '22 at 12:46
The warnings no doubt indicate your problem(s). The parameters to added_up() are int, not float. Turn up your compiler warning levels (max when you're learning the language) and pay attention to them. — Paul Lynch, Oct 29 '22 at 13:08
@Hermann12 warnings should most of the time be considered as error. Especially those containing the words _implicit_ and _defaults_. — Jabberwocky, Oct 29 '22 at 13:20
Add the options `-Wall -Wextra -Wpedantic` and you'll get more. Also add `-Werror` to turn all warnings into errors, which is a good habit, and actually *fix* the warnings. The compilers are very good at finding problems in your code. — Some programmer dude, Oct 29 '22 at 13:35

score 2 · Accepted Answer · edited Oct 29 '22 at 13:16

2

You must declare a function before using it
You have to define what type the function returns and you must define type of arguments you are passing to the function

#include <stdio.h>
float added_up(float a,float b); // 1)
int main()
{
  float a, b;
  a = 4.5;
  b = 9.6;

  printf("Result of %.2f + %.2f = %.2f", a, b, added_up(a, b));
  return 0;
}

/****************************************/

float added_up(float a,float b)// 2)
{
  float c=a+b;
  printf("Value a: %.2f \n", a);
  printf("Value b: %.2f \n", b);
  return c;
}

edited Oct 29 '22 at 13:16

Jabberwocky

48,281
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answered Oct 29 '22 at 13:05

Damian

56
3

With the comments from @Tom above I figured it out, too. For the main I used now 'void main(void) without 'rint main() and 'return 0''. I think a lot of flavors are available in C. – Hermann12 Oct 29 '22 at 13:15
2

@Hermann12 `int main(void)` is the correct way. – Jabberwocky Oct 29 '22 at 13:17
@Hermann12 `main` returns an `int`, which is the exit status. It will implicitly return a value of `0` (as a special case), but it should still be declared to return an `int` (as opposed to `void`). – Tom Karzes Oct 29 '22 at 13:23
@Jabberwocky thank you for editing answer. I am newbie user in Stack and i didn't know how to format answer :) – Damian Oct 29 '22 at 13:26

Function with variables in C

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