1.2.2 application generation

• translators are programs that convert source code into object code
• Compiler

  • translates high level code into machine code all at once
  • initial compilation process is longer than using other translators
  • compiled code is platform specific
  • compiled code can be run without a translator present
• Interpreter

  • translates and executes code line by line
  • produce an error if a line contains an error
  • slower than running compiled code
  • correct interpreter required to run on different platforms
  • code is platform independent
  • useful for testing code
• Assembler

  • low level language that is platform specific
  • translates assembly code into machine code
  • each line of assembly code is equivalent to almost one line of machine code
• Lexical analysis

  • whitespace and comments are removed
  • keywords and identifiers are replaced with tokens
  • information about tokens is stored in a symbol table
• Syntax analysis

  • tokens analysed against rules of the programming language
  • syntax errors are flagged up
  • abstract syntax tree is produced
• Code generation

  • abstract syntax tree used to produced machine code
• Optimisation

  • Aims reduce execution time
  • is a very time consuming stage
  • redundant parts of code are removed
• Linkers

  • software that links external modules and libraries included within the code
• Static linker

  • module/ library code is copied directly into the file
  • increases the size of the file
• Dynamic linker

  • addresses of modules/ libraries are added to the file
  • external module/ library updates automatically feed through to the main file
• Loaders

  • programs provided by the OS
  • fetches the library/ module from the given memory location
• Use of libraries

  • pre compiled programs which can be incorporated within other programs
  • error free
  • saves time and effort of developing and testing modules
  • can be reused across multiple programs