BCD

BCD

1. Binary Coded Decimal. A system of representing a decimal digit using four binary bits (a nibble):

0000 = 0  0001 = 1  0010 = 2  0011 = 3  0100 = 4
0101 = 5  0110 = 6  0111 = 7  1000 = 8  1001 = 9

with the nibbles 1010, 1011, 1100, 1101, 1110, 1111 not being used (i.e. A-F in hex). BCD has the advantage that when displayed in hexadecimal it reads as a decimal. For example the decimal number 42 would be represented in binary as 01000010 or in hex as 42.

2. Boot Configuration Data. On Windows Vista PCs the BCD is a database (using the same structure as the Windows registry) which contains information about each of the available boot options. Conceptually it replaces the "boot.ini" file that existed in previous versions of Windows, but unlike "boot.ini" it is not text editable.