Compiler construction niklaus wirth

Front ends and back ends.
This modern solution to the problem of porting a compiler reminds us of the technique which played a significant role in the propagation of Pascal around 1975 (Wirth, 1971).
The role of the structural tree was assumed by a linearized form, a sequence of commands of an abstract computer.

The source language used as a simple example was PL0, a subset of Pascal.
The target computer had a stack architecture similar to the P-code interpreter used for many Pascal implementations.
A strongly revised edition of the book appeared in 1995.
PL0 was replaced by Oberon-0, a subset of Pascal's descendant Oberon.