Programming languages

• Machine code

  • Binary representation of instructions
  • Formatted so CPU can decode and execute
  • Have an operation code instruction and address or data to use
• Low level languages

  • Written in Assembly code
  • Translated by an assembler into machine code
  • Code is fast to execute
  • Memory efficient
  • Code is harder to write and understand
  • The programmer works with memory directly
  • The code works on one type of processor only
  • One instruction translated into one machine code instruction
  • Used to instruct the hardware directly (embedded systems/device drivers)
• High level languages

  • Source code is written in languages (Python, C++, Java)
  • Translated by a compiler or interpreter into machine code
  • Writing computer programs is easier - uses commands similar to English
  • One source code instruction translates into many machine code instructions
  • Code will run on different types of processors
  • Programmer has lots of data structures to use
  • Code is quicker and easier to understand and write
  • Less memory efficient
  • Code can be slower to execute if not optimised
• Compilers

  • Translates source code from high-level languages into object code, then machine code - to be processed by CPU
  • The entire program is translated into machine code before it is run
• Compiler advantages

  • No need for translation software at run-time
  • speed of execution is faster
  • code is usually optimised
  • original source code is kept secret
• Compiler disadvantages

  • source code is easier to write in a high-level language, but the program will not run with syntax errors - difficult to write the code
  • code needs to be recompiled when the code is changed
  • designed for a specific type of processor
• Interpreter

  • Translates source code from high level languages into machine code - to be processed by the CPU
  • the program is translated line by line as the program is running
• Interpreter advantages

  • easy to write source code - program will always run, stopping when a syntax error is found
  • code does not need to be recompiled when the code is changed - easy to try out commands when the program has paused after finding an error
  • interpreted languages are easy for beginner programmers to learn to write code
• Interpreter disadvantages

  • translation software is needed at run-time
  • speed of execution is slower
  • code is not optimised
  • source code is needed