Can a compiler be made using QBasic?

[stylin]

Translating from a custom language to BASIC is one option, though you'll be limited to DOS-compatible targets. Another is to have your compiler output assembly language and either compile it with an external assembler or generate the machine code yourself. The speed of the resulting executable is then only limited to the assembly code you produce with your compiler, ie., it doesn't matter if you produce machine code in GW-BASIC, QBasic or Java; it all depends on your ability to generate fast assembly code. FreeBASIC was originally written in VB DOS, then as the language became more sophisticated was able to compile itself.