How do you create your own functions?

[bnhshallow]

Hey everyone, im trying to create my own functions but i cant find any books or anything that tells me how.
help me plz. thx, BNH

 

[programsecrets]

If all your code is in one file, then declare the function definition near the top and the implementation down below:


/* include files */
#include "stdio.h"


/* function definitions */
int MultiplyByTwo(int iValue);


/* main function */
int main()
{
int iMyValue = 25;
int iNewValue = 0;

/* call your function */
iNewValue = MultiplyByTwo(iMyValue);

/* use the new value however you want */
printf("%i multiplied by two is %i\n", iMyValue, iNewValue);
}


/* your function implementation /*
int MultiplyByTwo(int iValue)
{
return (iValue * 2);
}

If your code is split into separate files, then create a header file (i.e. MyApplication.h) and put the function definition (but not the implementation) in that file. #include "MyApplication.h" at the top of your main .c file and in any other .c file that uses your function.

 

[bnhshallow]

i tried your syntax but the compiler gave me warnings and removed the program. if its not too much trouble, do you think you could post an example sorce code.

Thanks

 

[programsecrets]

That *was* example source code.

Please tell me what warnings the compiler gave you.

It might be that it "removed the program" because the program actually ran okay within a dos window, but when it finished the dos window went away?

Are you in Windows using Microsoft Visual C++? Or Borland C? Or what...

 

[bnhshallow]

im using a program i downloaded from the internet called LCC-win32 or something like that. the warning was:
line 21: missing return value {

i just checked a lot of stuff and looked in the internal program launcher and it does work, but for some wierd reason id removes the program.

 

[programsecrets]

One thing I forgot that I should have added at the end of the main() function was the statement "return (0);" Here's the whole main() function again with that correction:


/* main function */
int main()
{
int iMyValue = 25;
int iNewValue = 0;

/* call your function */
iNewValue = MultiplyByTwo(iMyValue);

/* use the new value however you want */
printf("%i multiplied by two is %i\n", iMyValue, iNewValue);

return(0);
}


Also, if you *are* in Windows using Visual C++, set a "break point" on the newly added return(0) statement so the DOS window will stick around long enough for you to see the result.

 

[bnhshallow]

i Get it now thanks alot. i reread a part in "The absolute beginners Guide to C" and now its alot clearer.

Thanks.