32/64-Bit 80x86 Assembly Language Architecture

Chapter 15. Binary-Coded Decimal (BCD)

Converting an ASCII string to binary-coded decimal is as easy as pie (or is it a piece of cake?). In BCD, for every byte, the lower 4-bit nibble and upper 4-bit nibble each store a value from 0 to 9 (think double-digit hex only the upper six values A through F are ignored).

Workbench Files:\Bench\x86\chap15\project\platform

	project	platform
ASE to VMP	\ase2vmp\	\vc6
BCD 2N	\bcd\	\vc.net

BCD

Table 15-1. ASCII numerical digit to hex and decimal values

ASCII	0	1	2	3	4	5	6	7	8	9
Hex	0x30	0x31	0x32	0x33	0x34	0x35	0x36	0x37	0x38	0x39
Decimal	48	49	50	51	52	53	54	55	56	57
BCD	0	1	2	3	4	5	6	7	8	9
Binary	0000	0001	0010	0011	0100	0101	0110	0111	1000	1001

Converting a BCD value from ASCII to a nibble is as easy as subtracting the hex value of 0x30, '0', or 48 decimal from the ASCII ...