Kingy: Stoffel is telling you why what you're talking about happens. The information is useful because it explains why "if you put numbers larger than 127 in the array, they "wrap" into minus numbers." Note that, for an unsigned char, numbers larger than 255 "wrap" back to 0 and up. So (char)257 == 2.

You want a use for it? OK. Let's say you have a texture whose size is a power of two, say, 256 x 256. It is tiled. Now you want to find out, for a given x, y coordinate on that larger tiled surface, what the corresponding x, y coordinate is in your texture.

You could find x % 256, y % 256, or you could just find (char)x, (char)y, which would be much faster.

In fact, this technique is useful in dealing with anything that tiles, wraps, or repeats ad infenitum, and is a power of 4. Why a power of 4? Well, it's a power of two, for obvious reasons, because it's binary, but the size of data types increases by powers of two as well, so it has to be (n 2)2, or n4.

All integer data types - signed and unsigned char, short, int, long, and (on some compilers) __int64 (aka "long long") - "wrap around." They just "wrap" at higher numbers. Floating point data types - float and double (and, on some compilers, long double) - do not wrap, as far as I know.

Edited by - terranfury on August 5, 2001 4:47:59 PM