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42 - Really Getting Ahead I made some changes to SETTINGS.H, which you will find interesting.

#ifndef _SETTINGS_H //Defines are compiletime only variables. #define xsize 320 #define ysize 200 #define starnum 200 //------------------------------------------------------------------------- extern "C" void srand(int seed); extern "C" int rand(); extern "C" int time(int ptr); //------------------------------------------------------------------------- #define defkey(x, y) const int KEY_##x = y; defkey(esc, 0x01) defkey(til, 0x29) defkey(min, 0x0c) defkey(equ, 0x0d) defkey(bspace, 0x0e) defkey(tab, 0x0f) defkey(q, 0x10) defkey(w, 0x11) defkey(e, 0x12) defkey(r, 0x13) defkey(t, 0x14) defkey(y, 0x15) defkey(u, 0x16) defkey(i, 0x17) defkey(o, 0x18) defkey(p, 0x19) defkey(lsqrbrkt, 0x1a) defkey(rsqrbrkt, 0x1b) defkey(bslash, 0x2b) defkey(caps, 0x3a) defkey(a, 0x1e) defkey(s, 0x1f) defkey(d, 0x20) defkey(f, 0x21) defkey(g, 0x22) defkey(h, 0x23) defkey(j, 0x24) defkey(k, 0x25) defkey(l, 0x26) defkey(scln, 0x27) defkey(quot, 0x28) defkey(enter, 0x1c) defkey(lshift, 0x2a) defkey(z, 0x2c) defkey(x, 0x2d) defkey(c, 0x2e) defkey(v, 0x2f) defkey(b, 0x30) defkey(n, 0x31) defkey(m, 0x32) defkey(comma, 0x33) defkey(period, 0x34) defkey(fslash, 0x35) defkey(rshift, 0x36) defkey(ctrl, 0x1d) defkey(alt, 0x38) defkey(space, 0x39) defkey(up, 0x48) defkey(down, 0x50) defkey(left, 0x4b) defkey(right, 0x4d) //The following keys can't use the macro. #define KEY_1 0x02 #define KEY_2 0x03 #define KEY_3 0x04 #define KEY_4 0x05 #define KEY_5 0x06 #define KEY_6 0x07 #define KEY_7 0x08 #define KEY_8 0x09 #define KEY_9 0x0a #define KEY_0 0x0b //------------------------------------------------------------------------- extern "C" int easymode(); extern "C" char buffer[0xfa00]; extern "C" char keymap[0x80]; #endif #define _SETTINGS_H true

"#ifndef" is "if not #defined", which is a nifty little trick that we can use to ensure code is not "redefined" when included more than once by a single file. Next, we have macros (compile-time-only functions created with #define statements), which the syntax explains itself (outside of "##" which allowsed us to turn KEY_X into whatever we wanted it to be through "concatination after evaluateion"). I didn't test all these keys, but you'll find it fairly useful in the next lesson. Beware, macros and some of their functions cannot be relied on from compiler to compiler, and I also expect this behavior to change over time. However, they're very useful for making some repetitive tasks like this easier.

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