Decimal computer Decimal computer Decimal computers are computers which can represent numbers and addresses in decimal as well as providing instructions to operate on those numbers and addresses directly in decimal, without conversion to a pure binary representation. Some also had a variable wordlength, which enabled operations on numbers with a large number of digits. Early computers that were exclusively decimal include the ENIAC, IBM NORC, IBM 650, IBM 1620, IBM 7070. In these machines, the basic unit of data was the decimal digit, encoded in one of several schemes, including binary-coded decimal or BCD, bi-quinary, excess-3, and two-out-of-five code. Except for
Binary-coded decimal negative, and any other value is considered a positive sign value (the processors will normalize a positive sign to 1100 (C)). No matter how many bytes wide a word is, there are always an even number of nibbles because each byte has two of them. Therefore, a word of "n" bytes can contain up to (2"n")−1 decimal digits, which is always an odd number of digits. A decimal number with "d" digits requires ("d"+1) bytes of storage space. For example, a 4-byte (32-bit) word can hold seven decimal digits plus a sign, and can represent values ranging from ±9,999,999. Thus