Most computers use a coded version of true binary to represent characters. Many coding schemes have been developed over the years. The most popular is Binary Coded Decimal (BCD). In this a set of 4 to 6 bits is encoded. The most common method is to encode a pack of 2 numeric digits in an 8 bit byte called Packed Decimal. In another form straight binary string of a fixed set of bits; say 32, 36 or more are used.
The 4 bit positions of BCD are interpreted as a Straight Binary. It is known as Natural Binary Coded Decimal (NBCD). This is the most common code. The binary string encodes a quantity in the binary number system.
Extended Binary Coded Decimal Interchange Code (EBCDIC): There are also two popular 8 bit codes. This is used in IBM Mainframe models and in similar machines of other manufactures. It is called EBCDIC.
ASCII-8: In larger machines ASCII-8 an 8 bit version is used in data communication. This is used to represent data internally in PCs.
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