Compiler constuction lec 1 ( features of compiler and types of compiler).pptx
- 2. Scope • Introduction to Compiler • Why we construct compilers? • Features of Compiler • Types of Compilers • Decompiler • Cousins of Compiler
- 3. Do you know? What are the high or low level languages? Difference b/w them. Difference b/w Assembly and Machine language. What is the language of computer ? Why we feel easy in high level language ? What is language translator?
- 4. Compiler A compiler is a program that reads a program written in one language (i.e. source program) and translates it into equivalent program in another Language (i.e. the target language). Compiler Source program Target program
- 5. Compiler • The compiler reports to its user the presence of errors in the source program. Error Messages
- 6. Why we construct compilers? • Without compilers our machines (computers) are not able to understand the source code, written in high level language and thus required task will not get executed.
- 7. Features of Compiler • Correctness (preserve the meaning of the code) • Recognize legal and illegal program • Speed of target code • Good error reporting • Cooperation with the debugger • Manage storage of all variables and codes
- 8. Types of Compilers • Single Pass • Multi Pass
- 9. Single Pass Compiler • Single pass compiler is a compiler that passes the source code through each compilation unit only once. • It is faster and smaller than the multi pass compiler. • As a disadvantage of single pass compiler is that it is less efficient in comparison with multi pass compiler. • Single pass compiler is one that processes the input exactly once, so going directly from lexical analysis to code generator, and then going back for the next read.
- 10. Single Pass Compiler • Source program Compiler Target program
- 11. Multi Pass Compiler • A multi pass compiler separates compilation into multiple passes, where each pass would continue with the result of the previous pass. • Slower as each pass reads and write an intermediate file. • Memory consumption is high. • Take some times to compile. • Used to implement programing languages such as Java.
- 13. Decompiler • A program that translates from low level to higher level one is a decompiler. • It can be used for the recovery of lost source code, and is also useful in some cases for error correction. In case if the vendor of a software lose its source code ,they can use a decompiler to recover the source code from the executable. • It is an opposite of a compiler.
- 14. The Ethics of Decompilation • Is decompilation legal, and is it allowed? • There are many situations when decompilation can be used... • To recover lost source code. You may have written a program for which you only have the executable now (or you got the exe of a program you wrote long back, from someone else!). If you want to have the source for such a program, you can use decompilation to recover it. In all rights, you are the owner of the program, so nobody is going to question you.
- 15. The Ethics of Decompilation • Just as stated above, applications written long back for a computer may not have the source code now, and you may need to port it to a new platform. Either you have to rewrite the application from the scratch, or use decompilation to understand the working of the application and write it again.
- 17. Cousins of Compiler 1. Preprocessor It converts the HLL (high level language)into pure high level language. It includes all the header files and also evaluates if any macro is included. It is the optional because if any language which does not support #include and macro preprocessor is not required. 2. Compiler It takes pure high level language as a input and convert into assembly code. 3. Assembler It takes assembly code as an input and converts it into assembly code.
- 18. Cousins of Compiler 4. Linking and loading It has four functions: • Allocation: It means get the memory portions from operating system and storing the object data. • Relocation: It maps the relative address to the physical address and relocating the object code. • Linker: It combines all the executable object module to pre single executable file. • Loader: It loads the executable file into permanent storage.