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
Decimal do not allow an exact representation for all real numbers, so e.g. for the real number . Nevertheless, they allow approximating every real number with any desired accuracy, e.g., the decimal 3.14159 approximates the real , being less than 10 off; and so decimals are widely used in science, engineering and everyday life. More precisely, for every real number "x", and every positive integer "n", there are two decimals "l" and "u", with at most "n" digits after the decimal mark, such that "l" ≤ "x" ≤ "u" and ("u" – "l") = 10. Numbers are very often obtained as