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Introduction to Compilers

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Introduction to Compilers

  1. 1. Compiler Design (CSE-405-F) Akhil Kaushik Asstt. Prof., CE Deptt., TIT Bhiwani
  2. 2. Programming….Why?
  3. 3. What is a Compiler? • A compiler is a computer program (or set of programs) that transforms source code written in a high level language (the source language) into low level language (the target language may be assembly language or machine language (0,1)).
  4. 4. What is a Compiler?
  5. 5. What is a Compiler? Source Language Target Language
  6. 6. Introduction Compiler basically does two things: • Analysis: Compiling source code & detecting errors in it. • Synthesis: Translating the source code into object code depending upon the type of machine.
  7. 7. Introduction • Program errors are difficult to track, if the compiler is wrongly designed. • Hence, compiler construction is a very tedious and long process.
  8. 8. One-pass Compiler • It compiles the that passes through the source code of each compilation unit only once. • They are faster than multi-pass compiler. • Their efficiency is limited because they don’t produce intermediate codes which can be refined easily. • Also known as ‘Narrow Compiler’.
  9. 9. Multi-pass Compiler • It processes the source code or abstract syntax tree of a program several times. • It may create one or more intermediate codes (easy to refine). • Each pass takes output of previous phase as input; hence requires less memory. • Also known as ‘Wide Compiler’.
  10. 10. Type of Languages 1. Binary Level Language 2. Assembly Level Language 3. High Level Language
  11. 11. Need for programming languages? • Closer to human thinking behavior. • Program’s size is shorter. • Error detection is easy. • Same program can be compiled in accordance to different machine architectures.
  12. 12. History • Software for early computers were written in assembly language. • The need of reusability of code gave birth to programming languages. • This need grow huge to overcome the cost restriction of compiler.
  13. 13. History • The concept of machine independent programming gave birth to the need of compilers in 1950s. • The 1st compiler was written by Grace Hopper in 1952 for A-0 programming language.
  14. 14. History • The 1st complete compiler was developed by FORTRAN team lead by John Backus @ IBM in 1957. • COBOL was the 1st language to be compiled on multiple platforms in 1960.
  15. 15. History • Earlier compilers were written in assembly languages. • The 1st compiler in HLL was created for LISP by Tim Hart & Mike Levin @ MIT, USA in 1962, which was a self-hosting Compiler.
  16. 16. History • Most compilers are made in C or Pascal languages. • However the trend is changing to self-hosting compilers, which can compile the source code of the same language in which they are created.
  17. 17. Why Study Compiler? • Its essential to understand the heart of programming by computer science engineering students. • There may be need of designing a compiler for any software language in the profession.
  18. 18. Why Study Compiler? • Increases understanding of language semantics. • Helps to handle language performance issues. • Opportunity for non-trivial programming project
  19. 19. Translators • It is important to understand that compiler is a kind of translator, which translates high level language (human understandable) to low-level language(machine understandable).
  20. 20. Translators
  21. 21. Translators - Preprocessor • It is a program that processes its input data to produce output that is used as input to another program. • The output is said to be a preprocessed form of the input data, which is often used by some subsequent programs like compilers.
  22. 22. Translators - Preprocessor • The amount and kind of processing done depends on the nature of the preprocessor. • some preprocessors are only capable of performing simple textual substitutions and macro expansions, while others have the power of full- fledged programming languages. • It can also include macro processing, file inclusion and language extensions.
  23. 23. Translators - Interpreter • It is another common kind of language processor. • Instead of producing a target program as a translation, it directly execute the operations specified in the source program on inputs supplied by the user.
  24. 24. Translators - Interpreter • This software converts the high-level language into low-level language line by line. • It takes less memory than compiler. • It takes more time than compiler. • It is more efficient in error detection than compiler. • It takes more time to build.
  25. 25. Translators - Interpreter • Java language processors combine compilation and interpretation. • A Java source program may first be compiled into an intermediate form called bytecodes. • The bytecodes are then interpreted by a virtual machine. • A benefit of this arrangement is that bytecodes compiled on one machine can be interpreted on another machine, perhaps across a network.
  26. 26. Translators - Interpreter
  27. 27. Translators - Assembler • This software converts the assembly language (assembly instruction mnemonics) into machine level language (opcodes i.e. 0,1). • It offers reusability of assembly codes on different machine platforms.
  28. 28. Translators - Assembler • It generates instructions by evaluating the mnemonics (symbols) in operation field and find the value of symbol and literals to produce machine code. • Now, if assembler do all this work in one scan then it is called single pass assembler, otherwise if it does in multiple scans then called multiple pass assembler.
  29. 29. Translators - Assembler • Pass-1: – Define symbols and literals and remember them in symbol table and literal table respectively. – Keep track of location counter – Process pseudo-operations • Pass-2: – Generate object code by converting symbolic op-code into respective numeric op-code – Generate data for literals and look for values of symbols
  30. 30. Translators - Assembler
  31. 31. Translators - Linker • A linker is a program that allows a user to link library programs or separate modules of code into their own programs. • It is used to combine different modules of object code into one single executable code program.
  32. 32. Translators - Linker • This may involve combining a program with library programs, or involve recombining blocks of object code from the same program, or a mixture of both. • The linker program is used to recombine the blocks of object code in RAM to get a working full program. • Linker is helpful if there is a shortage of RAM.
  33. 33. Translators - Loader • A loader is a piece of software that chooses exactly where to put object code in RAM, ready for it to be run. • It also adjusts the memory references in programs.
  34. 34. Translators - Loader • Programs can be written by programmers using either ‘absolute addressing’ or ‘relative addressing’. • Relative addressing is more common because then the loader can put the program anywhere in RAM - absolute addressing isn't flexible. • Linker & Loader may overlap.
  35. 35. Translators - Loader
  36. 36. Translators - Cross-Compiler • If the compiled program can run on a computer whose C.P.U or O.S is different from the one on which the compiler runs, the compiler is known as a cross-complier.
  37. 37. Translators - Cross-Compiler
  38. 38. Translator – Language Converter • Also called Language Translator / Source to source translator. • It converts programs in one high-level language to another high-level language. • Ex: Cfront converts C++ into C language.
  39. 39. Translator – Language Rewriter • It is a program that changes form of expression of the same language. • It does not changes the language of source code.
  40. 40. Translator - Decompiler • It is a piece of software that converts the low-level language to high-level language . • It is not as famous, but may prove a useful tool sometimes. • Ex: JD Compiler, .JAD decompiler, NET Reflector
  41. 41. Translator – Compiler-Compiler • It is a tool that creates a compiler, interpreter or parser from the information provided on formal description of any language. • The earliest & most common type is parser- generator. • It is also called compiler-generator. • Ex: Yacc, JavaCC, etc.
  42. 42. CONTACT ME AT: Akhil Kaushik akhilkaushik05@gmail.com 9416910303 CONTACT ME AT: Akhil Kaushik akhilkaushik05@gmail.com 9416910303 Thank You !!!

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