編譯原理概述ppt課件-wenkub.com
2024-12-05 05:40 本頁(yè)面
【正文】 a[R0], 6 。 add R0 to R1 MOV *R1, 6 。 value of index R0 MUL R0, 2 。Chapter 1 Introduction Instructor Jianhui Yue Software College SCU Office : JCB321 Outline ? 1 Conceptions ? 2 Compiler Processes Overview ? 3 Suggestions on how to study this course Compilers ? Compilers are puter programs that translate one language to another . – Very plex program from 10,000 to 1,000,000 lines of code. ? Its input is a program written in its source language. – Usually, the source language is a highlevel language (C, C++, etc). ? It produces an equivalent program written in its target language. – The target language is object code (machine code) for the target machine. Machine Language ? Initially, the programs were written in machine language – numeric codes that represented the actual machine operations to be performed. ? C7 06 0000 0002 moves number 2 to the location 0000. ? Writing such codes is time consuming and tedious. Assembly Language ? In assembly language instructions and memory locations are given symbolic forms. MOV X, 2 ? An assembler translates the symbolic codes and memory locations into corresponding numeric codes. ? Advantages: – Great improvement in speed and accuracy of writing programs. – still used today. ? Disadvantages: – Still not easy to write and difficult to read and understand. – Machine dependent. Highlevel Languages ? Nearly resembles mathematical notation or natural language. ? Independent on any particular machine. ? Capable of being translated into executable code X = 2 ? Need a program that performs translation. ? Is it possible? Is generated object code efficient? Theoretical Foundations ? Noam Chomsky’s study of the structure of natural languages. – Classification of languages according to the plexity of their grammars and the algorithms to recognize them. ? Contextfree grammars are the most useful for programming languages – Study of the parsing problem, which bee a standard part of piler theory. ? Study of finite automata and regular expressions. – Led to symbolic methods for expressing the structure of words of a programming language ? Optimization techniques (code improvement techniques). Interpreters ? An interpreter is a language translator like a piler. ? The difference: the source program in executed immediately, not after translation is plete. ? Programming language can be either interpreted or piled. ? Interpreted languages: BASIC, LISP, Java ? Compiled languages: FORTRAN, C, C++. ? Interpreters share many operations with pilers. Assemblers ? An assembler is a translator for the assembly language of a particular puter. ? Assembly language is a symbolic form of the machine language and it is easy to translate. ? Sometimes, a piler will generate assembly language as its target language. ? Then assembler will finish the translation into object code. Linkers ? A linker collects code separately piled or assembled in different object files into final executable file. ? Also connects to the code for standard library functions and to resources supplied by OS (memory allocators, I/O devices) ? A linker was originally one
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