Writing a compiler is a quite complicated task, one will usually prefer to write it in a high-level language. A possible choice is to use a language that is already available on the machine where the compiler should eventually run.
To reduce the designing effort and to bring qualitative improvement a technique is introduce. Such technique is called Bootstrapping of a compiler.

A compiler is based on three languages :-

1. Source Language
2. Target Language
3. Implementation Language

For designing a compiler we use some notation :-

1. ”S”   for Source Language.
2. ”T”   for Target Language.
3. ”I”    for Implementation Language.

A compiler is denoted through two notation:1.Simple notation
                                 

1. Create , a compiler for a subset "S" of the desired language "L" using language "A", which runs on machine "A". (Language "A" may be assembly language.)                                                                               
2.  Create , a compiler for language "L" written in a subset of "L".                                                                                  

3.  Compile  using to obtain , a compiler for language "L", which runs on machine "A" and produces code for machine "A".