10进制0到255的16进制转换，懒得算了，遇到时查查！

0 -> 00;   1 -> 01;   2 -> 02;   3 -> 03;
4 -> 04;   5 -> 05;   6 -> 06;   7 -> 07;
8 -> 08;   9 -> 09;  10 -> 0A;  11 -> 0B;
12 -> 0C;  13 -> 0D;  14 -> 0E;  15 -> 0F;
16 -> 10;  17 -> 11;  18 -> 12;  19 -> 13;
20 -> 14;  21 -> 15;  22 -> 16;  23 -> 17;
24 -> 18;  25 -> 19;  26 -> 1A;  27 -> 1B;
28 -> 1C;  29 -> 1D;  30 -> 1E;  31 -> 1F;
32 -> 20;  33 -> 21;  34 -> 22;  35 -> 23;
36 -> 24;  37 -> 25;  38 -> 26;  39 -> 27;
40 -> 28;  41 -> 29;  42 -> 2A;  43 -> 2B;
44 -> 2C;  45 -> 2D;  46 -> 2E;  47 -> 2F;
48 -> 30;  49 -> 31;  50 -> 32;  51 -> 33;
52 -> 34;  53 -> 35;  54 -> 36;  55 -> 37;
56 -> 38;  57 -> 39;  58 -> 3A;  59 -> 3B;
60 -> 3C;  61 -> 3D;  62 -> 3E;  63 -> 3F;
64 -> 40;  65 -> 41;  66 -> 42;  67 -> 43;
68 -> 44;  69 -> 45;  70 -> 46;  71 -> 47;
72 -> 48;  73 -> 49;  74 -> 4A;  75 -> 4B;
76 -> 4C;  77 -> 4D;  78 -> 4E;  79 -> 4F;
80 -> 50;  81 -> 51;  82 -> 52;  83 -> 53;
84 -> 54;  85 -> 55;  86 -> 56;  87 -> 57;
88 -> 58;  89 -> 59;  90 -> 5A;  91 -> 5B;
92 -> 5C;  93 -> 5D;  94 -> 5E;  95 -> 5F;
96 -> 60;  97 -> 61;  98 -> 62;  99 -> 63;
100 -> 64; 101 -> 65; 102 -> 66; 103 -> 67;
104 -> 68; 105 -> 69; 106 -> 6A; 107 -> 6B;
108 -> 6C; 109 -> 6D; 110 -> 6E; 111 -> 6F;
112 -> 70; 113 -> 71; 114 -> 72; 115 -> 73;
116 -> 74; 117 -> 75; 118 -> 76; 119 -> 77;
120 -> 78; 121 -> 79; 122 -> 7A; 123 -> 7B;
124 -> 7C; 125 -> 7D; 126 -> 7E; 127 -> 7F;
128 -> 80; 129 -> 81; 130 -> 82; 131 -> 83;
132 -> 84; 133 -> 85; 134 -> 86; 135 -> 87;
136 -> 88; 137 -> 89; 138 -> 8A; 139 -> 8B;
140 -> 8C; 141 -> 8D; 142 -> 8E; 143 -> 8F;
144 -> 90; 145 -> 91; 146 -> 92; 147 -> 93;
148 -> 94; 149 -> 95; 150 -> 96; 151 -> 97;
152 -> 98; 153 -> 99; 154 -> 9A; 155 -> 9B;
156 -> 9C; 157 -> 9D; 158 -> 9E; 159 -> 9F;
160 -> A0; 161 -> A1; 162 -> A2; 163 -> A3;
164 -> A4; 165 -> A5; 166 -> A6; 167 -> A7;
168 -> A8; 169 -> A9; 170 -> AA; 171 -> AB;
172 -> AC; 173 -> AD; 174 -> AE; 175 -> AF;
176 -> B0; 177 -> B1; 178 -> B2; 179 -> B3;
180 -> B4; 181 -> B5; 182 -> B6; 183 -> B7;
184 -> B8; 185 -> B9; 186 -> BA; 187 -> BB;
188 -> BC; 189 -> BD; 190 -> BE; 191 -> BF;
192 -> C0; 193 -> C1; 194 -> C2; 195 -> C3;
196 -> C4; 197 -> C5; 198 -> C6; 199 -> C7;
200 -> C8; 201 -> C9; 202 -> CA; 203 -> CB;
204 -> CC; 205 -> CD; 206 -> CE; 207 -> CF;
208 -> D0; 209 -> D1; 210 -> D2; 211 -> D3;
212 -> D4; 213 -> D5; 214 -> D6; 215 -> D7;
216 -> D8; 217 -> D9; 218 -> DA; 219 -> DB;
220 -> DC; 221 -> DD; 222 -> DE; 223 -> DF;
224 -> E0; 225 -> E1; 226 -> E2; 227 -> E3;
228 -> E4; 229 -> E5; 230 -> E6; 231 -> E7;
232 -> E8; 233 -> E9; 234 -> EA; 235 -> EB;
236 -> EC; 237 -> ED; 238 -> EE; 239 -> EF;
240 -> F0; 241 -> F1; 242 -> F2; 243 -> F3;
244 -> F4; 245 -> F5; 246 -> F6; 247 -> F7;
248 -> F8; 249 -> F9; 250 -> FA; 251 -> FB;
252 -> FC; 253 -> FD; 254 -> FE; 255 -> FF;
C语言：
#include <stdio.h>
main()
{
int a = 0;
while (a < 256)
{
  printf("= -> %.2X; ", a, a);
  if (a%4 == 3)
  {
   printf("\n");
  }
  a++;
}
}