I like the error messages in some early BASIC interpreters. They must be as short as possible, since the entire interpreter fits in 4 KiB of RAM. For example, in Li-Chen Wang's Palo Alto Tiny BASIC...

The only message for all syntax errors, is:

    WHAT?

The only message for all runtime errors, is:

    HOW?

And the only message for legal but unsupported operations (e.g. out of memory) is:

    SORRY

See the source code here: https://github.com/ancientcomputing/8080_8085/blob/master/Ti...