Two: "0" and "1." Digital (as opposed to analogue) computers all use binary arithmetic/notation, which is positional like decimal arithmetic/notation, but employs only two tokens (0, 1) in place of decimal's ten (0 .. 9). The term "bit" for the smallest unit of information, incidentally, is a contraction of the phrase "binary digit."
The number of 4 digit codes, using different digits, is 10*9*8*7 = 5040. However, computer passwords can, usually, have repeated digits and, if that is allowed, you can have 104 = 10000 codes.
An example for computer networking question is: how many digits of the DNIC identify the country? Another asks for how many routing algorithms are used.
how is it possible that modern computer systems rely on only two digits?
how many generations of computer languages have there been since the middle of the 20th century
A digital computer is that one which represents the information by the binary digits.
6 digits
6
Desktop Gizmodo
12 digits.12 digits.12 digits.12 digits.
A quadrillion has 16 digits.
Seven digits.
6 digits