How can an api be accessed through other languages

I didn't really know up until a little while ago that an api can be accessed through other languages. In a visual C++ book I am reading it says that the winapi can be accessed through visual basic (duh) but also fortran, pascal, and other languages. How is it possible to make calls to the winapi (which is written mostly in C, right?) with languages such as fortran and pascal?

well win32 api is compiled as libraries wich you can link to just about anything since they're modules.. include the header for the apropriate language to get the prototypes of the win32api and link with the libraries you want and then you're ready make calls to them..
haven't really done this in either fortran or pascal but I've done it in asm and that's the principle...

maybe I'm wrong but I hope this somewhat helps..:)

/btq

Hmm okay so are you saying the Microsoft people wrote libraries for every language?

no, I'm saying they didn't have to bother ;)
a DLL that exports its functions can be used by every language
(maybe to some extent?).

if you write a simple library with a function called:
int ret(); that returns the value 4 everytime it's called and export this function, you can use it in every langauge with the apropriate prototype of this function and the propriate linking.

for instance in masm you use this as the prototype for SetPixel:
SetPixel PROTO :DWORD,:DWORD,:DWORD,:DWORD

which is a function exported by Gdi32.dll.
With this and linking with the Gdi32 library, you can use this function of the library..

it doesn't really matter in which language you make the library in this aspect..

hope this helps :)

/btq

This idea is still somewhat hazy. Where, exactly, does the conversion from a C++ prototype to an assembly prototype take place? (I didn't know assembly had functions, I know nothing of the lower level languages).

if the cpp prototype is:
void SetPixel(x)
How does it go from that to
SetPixel PROTO :DWORD,:DWORD,:DWORD,:DWORD

Does the masm linker automatically read through it and convert it for you?

Yes you are helping!

the prototype for SetPixel is

Code:

---

COLORREF SetPixel(
    HDC hdc,        // handle of device context 
    int X,        // x-coordinate of pixel
    int Y,        // y-coordinate of pixel
    COLORREF crColor        // pixel color
  );

---

and this prototype would in masm look like:
SetPixel PROTO :DWORD,:DWORD,:DWORD,:DWORD
(in masm this is only used for macros such as Invoke which calls the function, though normally you just push the params on the
stack and call the functions etc. so that was a bad example. )

but think of it as a c++ source file. You have a c++ source file with a
simple function. To use this function in another c++ sourcefile you
need to include the c++ header file(which contains the prototype).
this is kinda similar for load-time libraries. You need to know the
prototypes of the functions to be able to use them...
and these prototypes must be written in the language you're within..
the functions that resides in the DLL doesn't care from what
language you're calling them as long as they get the proper
params pushed onto the stack etc..

/btq

Ok that makes more sense to me now, cool