Data - Coding systems
BCD | Extended character set | EBCDIC | ASCII (Special characters) | Answers

Encoding text data - bcd

Character storage

With the advent of text processing a method was needed to store

ALPHABETIC CHARACTERS
= A..Z

SPECIAL CHARACTERS
= !@#$%^&*()-+=[]:;"',.<>/?.

Hence, two further bits were added to the front of the numeric bits (called "zone" bits) to enable the representation of these characters.
This code became what is commonly referred to as the BCD Code.

[Encoding data cartoon]

Binary Coded Decimal (BCD)

BCD - using two 'zone' bits, a 6 bit code was used by many early machines (and some 3rd Generation computers (eg. ICL 1900)).

For example

B	A	8	4	2	1
0	0	0	0	1	1	--> 3
0	0	1	0	0	1	--> 9
Zone		numeric

Note that only 64 characters may be represented. (2^6), and that lowercase letters were not represented. Many printers were constructed to output only standard BCD characters, and many texts on COBOL programming still use uppercase only in their code. (COBOL 85 now allows for mixed case programming).