funtion reuse

Hi everyone, I've just started learning C.
I'm trying to figure out one thing, if I have a program, say myprogram.c with a main and a bunch of functions in it, how could I take out function1 save it in a file say myfunction.c and have myprogram.c see function1?

I know this is a very basic question, I'm just starting out, thank you for any reply.

Regards,
Luca.

You would use a .h file...

1) Save the function(s) to their separate C page.
2) Create a new .h file with function prototypes in it
3) Include it into your main source page.

Code:

---

// functions.c

int add(int x, int y)
  { return x +  y; }

int multiplay (int x, int y)
  { return x * y; }

////////////////////////////////////////////////////////////////////////
// functions.h

int add(int x, int y);    // ---- Note the semicolon.
int multiply(int x, int y);


//////////////////////////////////////////////////////////////////////////
// main.c

#include "functions.h"  // --- note quotes not brackets

int x, y;

x = add(7,4);

y = multiply(3,2);

---

... and somehow coax the IDE to add the new .c source to the project.

Quote:

---

Originally Posted by nonoob

... and somehow coax the IDE to add the new .c source to the project.

---

Thanks... I forgot to mention that.

I tried to follow the steps but I'm getting this error
"undefined reference to 'WinMain@16'" while I try to compile stringutils.c, here's the code

stringutils.c

Code:

---

#include <stdio.h>
#include <string.h>

#define MAXLEN 1000 /* max length of any input line */
int getline(char *, int);
char *alloc(int);

/* readlines: read input lines */
int readlines(char *lineptr[], int maxlines)
{
  int len, nlines;
  char *p, line[MAXLEN];
 
  nlines = 0;
  while((len = getline(line, MAXLEN)) > 0)
    if(nlines >= maxlines || (p = alloc(len)) == NULL)
      return -1;
    else
    {
      line[len-1] = '\0'; /* delete newline */
      strcpy(p, line);
      lineptr[nlines++] = p; 
    } 
  return nlines;   
}

/* writelines: write output lines */
void writelines(char *lineptr[], int nlines)
{
  int i;
 
  for(i = 0; i < nlines; i++)
    printf("%s\n", lineptr[i]); 
}

/* getline: get line into s, return length */
int getline(char s[], int lim)
{
  int c, i;

  i = 0;
  while(--lim > 0 && (c = getchar()) != EOF && c != '\n')
    s[i++] = c;
  if(c == '\n') 
    s[i++] = c;
  s[i] = '\0';
  return i;
}

char * alloc(int n)
{
}

---

here is the header file

stringutils.h

Code:

---

int readlines(char *lineptr[], int nlines);
void writelines(char *lineptr[], int nlines);

---

I'm using Dev-C++ to edit and compile the source files

> "undefined reference to 'WinMain@16'" while I try to compile stringutils.c, here's the code
You created a GUI project, but you should have created a "Win32 Console" project.

You might be able to change the project type, but it's usually simpler just to create a new project with the right type (console), and then add your single source file to that.

That's fine now.
Thank you very much.