I recently a seat booking C program for a college assignment. I've been told since by the tutor that my use of globals is bad, and I should use local variables, passing them as function parameters to any functions that need them. To me, that looks messy. While I understand the overuse of globals is a bad idea because of memory use and function portability, I think they're necessary sometimes to avoid unnecessarily large parameter lists. Personally I'd have preferred to program the thing in C++ and put the whole thing in a class anyway, but this was a C only project. I was just wondering what your opinions were. The two globals are

int seat_allocated[12]; char seatStr[2][20]={{"NON-SMOKING"},{"SMOKING"}};

There are about 10 functions in my program, many of them using the two globals above. If you want the rest of the source, look here. www.elf-stone.com Edited by - benjamin bunny on May 17, 2001 6:44:56 PM

If you''re plagued with long function calls, you could add IO container classes. It helps prevent breaking interfaces also. So a call to (in VB-esque pseudo code):

someoutput = MyFunc(var1,var2,var3,var4,var5)

becomes

FuncRequest.var1 = "a" FuncRequest.var2 = "b" FuncRequest.var3 = "c" FuncRequest.var4 = "d" FuncResponse = MyFunc(FuncRequest)

Hope that helps.

Epolevne

The first variable should be avoided if possible or atleast be placed inside its own module. The second is more of constant and that is ok. I would however prefer a "const" in front of it.

I learnt from ''Code Complete'' that if your function lists are long you probably have a bad design. Try breaking up what your doing in a manner that stops you from having to pass the extra params.

Personally I have no globals in my 160 file application. Almost no static''s, and nothing extern''ed.

My personal limit is around 5, they say 7+ is bad. If you need more that that you should either break up the code or pass in a struct. For example rather than passing in all the attributes of a screen like height,width, colours, fullscreen, vsync, I make a class(struct in C) and pass that in by reference(pointer in C).

In C I found it harder to avoid globals than in C++ as C++ has member vairables which in my mind are just globals with a scope of the class (ie the are shared amongst many functions like a global might be).


HTH