The word ‘‘virtual’’ appears frequently throughout the computer literature in many
different contexts.
In optics, a virtual image is the reflection that you see when you stand in front of a
regular mirror.You know that the image isn’t real. For one thing, it’s behind the wall that the mirror is mounted on.
For another, you can’t touch it. In early, time-shared computing, a large central computer
commonly supplied computing services to users at terminals located remotely from the
computer. In a sense, it seemed as though the user had access to a computer that was all her
own.