Q:

Dev C++ to compile C source file

How can I use Dev C++ to compile C source file. I thought it would automatically do it, but for some reason it  compiles with several errors and I think its because you have to make changes for it to compile a C file.
Example test code:
 #include <stdio.h>

main ()        
{ int i,j;
double x,x_plus_one();
char ch;

i = 0;
x = 0;

printf (" %f", x_plus_one(x));
printf (" %f", x);

j = resultof (i);

printf (" %d",j);
}

double x_plus_one(x)          

double x;

{
  x = x + 1;
  return (x);
}

resultof (j)             

int j;

{
   return (2*j + 3);       
}

A:

That is pre-ANSI code. I'm not sure the gcc compiler supports it, and in any case it is bad practice to use it. Change your function to:
double x_plus_one( double x) {
  x = x + 1;
  return (x);     
}

and you will need to declare it as:
double x_plus_one( double x);

You may also want to try compiling with the -traditional flag, but I haven't tested this.

