HEXADECIMAL
NUMBERS
Come back. You don't have to run away at the sound of those words. Hex, as its friends call it, is not nearly as hard as everyone thinks it is. As a matter of fact, it's really quite simple. But, just in case you don't believe us, I provide both decimal and hexadecimal numbers throughout the book. Now, though, we're going to learn about hex together.
The main use for hex is in assembly language programming. We're not going to worry about that now though, because it's not really important. Instead, we're going to go back to grade school, where we first learned all about the number system. As you'll recall, we use the decimal number system, which means that everything is based on powers of 10. For example, the number 452 is equal to 4*100+5*10+2*1, right? In other words, 4*10^2+5*10^1+2*10^0. Now you're not going to believe this, but the only difference between decimal and hex is that hex is based on powers of 16 instead of 10. For example, 452 hex would equal 4*16^2+5*16^1+2*16^0 or 4*256+5*16+2, in other words, 1106. Pretty simple, huh? Actually, there's one more thing that I should probably mention. The number 9 in hex is the same as 9 decimal, but 10 hex is 16 decimal (1 * 16^ 1). So how do you write 10, 11, 12, 13, 14, and 15 decimal in hex? Try A, B, C, D, E, and F! That's why hex numbers look so confusing. So, for example, F in hex equals 15 decimal, 1F equals 31 (16+15), and so on. Oh, and by the way, binary is actually the same as hex and decimal, except it counts in powers of 2!
Don't worry, I'm not going to leave you yet. A few more examples should make you a little more comfortable about hex and how to use it, but first a chart (Table 1) to help us out.
Table
1. Hex Conversion Chart
Column # 
4th 
3rd 
2nd 
1st 
# HEX 


4096 8192 12288 16384 20480 24576 28672 32768 36864 40960 45056 49152 53248 57344 61440 
256 512 768 1024 1280 1536 1792 2048 2304 2560 2816 3072 3328 3584 3840 
16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 
1 2 3 4 5 6 7 8 9 A B C D E F 
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