Compiler¶
Translates human-oriented programming languages into computer-oriented machine languages.
A compiler allows virtually all computer users to ignore machine independent details of machine language.
- Making programs and programming expertise portable across wide variety of computers.
Compiler Distinction
Compilers may be distinguished by:
- By the kind of machine code they generate
- By the format of the target code they generate
Machine Code Generated by Compilers¶
May generate any of three:
- Pure Machine Code
- Augmented Machine Code
- Virtual Machine Code
Pure Machine Code¶
Code for a particular machines instruction set.
Called pure code, because it only includes instructions part of that instruction set.
Rare because most compilers rely on runtime libraries and OS's
Most commonly used in compilers for system implementation languages, which are inteded for implementing OS's ore embedded applications.
Can execute on bare hardware without dependence on any other software.
Augmented Machine Code¶
Augmented with OS routines and runtime language support routines.
Requires that a particular OS be present.
Virtual Machine Code¶
Consists of entirely of virtual instructions.
- Increases portability
An interpreter for the virtual machine (VM) is written for every target architecure.I
Example: Java
Bootstrapping a Compiler¶
If a compiler accepts source language L. Any instance of this compiler can translate from L to VM instructions.
If the compiler itself is written in L, the compiler can compile itself into the VM instructions.
Language Criteria¶
Sebesta's Language Criteria
