Thread: A few questions...

Hi there. If you want to add more than 1 to the variable a you could use
a += 5;
This is the same as saying
a = a + 5;


OpenGL is an API (Application Programming Interface) for doing graphics, especially games. Basically you include the opengl header files, and then you link the opengl libraries, and once you have done that you can write graphics programs. It takes quite a while to learn how to use all of the functions in the opengl libraries (there are altogether several hundred functions that make up OpenGL). I don't know how in depth you wanted to get on this topic, but DirectX is the name given for several libraries, the X is actually a variable ( I dont' know if you knew that or not).
The libraries for DirectX are:
DirectDraw/Direct3d (the graphics parts of DirectX)
DirectSound/DirectMusic (the sound parts of DirectX)
DirectInput (used for special features on game controllers, i.e force feedback for joysticks in fighter pilot games)
DirectPlay(the networking portion of DirectX...used for multiplayer games across LANs and the Internet)
DirectShow(used for playing video files such as AVIs and MPGs)
DirectSetup(Helps installing directx features)

DirectX is available only for the Windows operating systems, but includes not just a graphics libraries, but also all of those other ones. OpenGL is available for almost any operating system, but is only a graphics library and must use other libraries to achieve all the rest of the functionality required.
Ok, I'll shut up now...I really hope I helped somewhat.

as long as the function prototype is seen by the compiler before the first call to that function you're home free. Traditionally the prototypes are located where you suggest or in header files however. They can be anywhere in the program however.

The += must be overloaded for the variable type you are trying to use it with in order for it to work. It works fine for all the primitive variables, including char, since it comes already overloaded for you, but it may not do what you think it does with type char so if used in that context be forewarned.

functions manipulate data. One place functions can get data is from local variables. Another is from global variables. The third is to be passed data from the calling function. By definition the calling function must pass a variable of some type to the called function. the variable types that need to be passed to a given function are called parameters when they are listed in the function prototype/definition and arguments when you actually pass them during the function call, or maybe it's the other way way around. unless you are working in some rarefied environment however it doesn't make a lot of difference which term you use. Note that void is a valid variable type meaning no actual data is being passed, and if the () following the function name is empty a variable of type void is implied.