A computer is a mechanism which has a universal information-processing capability.
Provided that sufficient memory is available, it is possible to implement (emulate) any computer within any other computer. This is the principle of computational equivalence.
The most important type of computer for a human being is, of course, the human brain. All individual human brains are subprocessors of another important computer, the Universe.
In Baktun 12, human beings learned to build artificial automatic computers of their own. These devices can be very useful in some areas of self-cultivational practice, but they are by no means mandatory for attaining enlightenment.