Programming Languages

Programming Languages

1. High-Level Languages

   • one instruction of high-level code represents many instructions of machine code
   • the same code will work for many different machines and processors
   • the programmer can easily store data in lots of different structures (e.g. lists and arrays) without knowing about the memory structure
   • code is easy to read, understand and modify
   • must be translated into machine code before a computer is able to understand it
   • you don't have much control over what the CPU actually does so programs will be less memory efficient and slower

2. Low-Level Language

   • one instruction of assembly code usually only represents one instruction of machine code
   • code is very difficult to read, understand and modify
   • usually written for one type of machine or processor and won't work on any other
   • the programmer needs to know about the internal structure of the CPU and how it manages the memory
   • commands in machine code can be executed directly without the need for a translator
   • you control exactly what the CPU does and how it uses memory so programs will be more memory efficient and faster

3. Translators

   • Compiler
     • translates all of the source code at the same time and creates one executable file
     • only needed once to create the executable file
     • returns a list of error for the entire program once compiling is complete
     • once compiled the program runs quickly, but compiling can take a long time
   • Interpreter
     • translates and runs the source code one instruction at a time, but doesn't create an executable file
     • needed every time you want to run the program
     • the interpreter will return the first error it finds and then stop - this is useful for debugging
     • programs will run more slowly because the code is being translated as the program is running

4. Opcode

   • specifies the code of the operation that is to be performed. (E.G. add/subtract numbers or store data in a memory location).
   • Operand
     • - the values that is to be used. - the memory location in which the data can be found or has to be stored. (1101 could mean the value 13 or at memory location 13)