Machine code
- Instructions in binary, that a processor can execute directly (low level)
- produced by compiler, interpreter or assembler
Low-level language
- The computer’s own language
- In binary numbers
Opcode
The part of the instruction that tells the CPU what operation is to be done
Operand
The part of the instruction that tells the CPU what to apply the operation to
Instruction set
The complete set of instructions that a processor can handle
High-level language features
- One-to-many: programmer doesn’t need to write every single instruction carried out by the processor as one statement translate into many machine code instructions
- programs are much shorter and easier to read, right and handle
- problem-oriented: the programmer can concentrate on the logic of the problem
- Easier to learn and understand and debug
- translated using a compiler or interpreter
- Machine independent: the same program can be run in many different computer platforms without needing to change the code
Advantages of low-level language
- doesn’t need to be translated
- direct control of hardware/memory
- faster execution
- can program for specific hardware
Disadvantages of low-level languages
- Difficult to use because every single instruction has to be specified by the programmer
- The code is specific to a particular processor, so a program would need to be rewritten to be run in a different computer
Translation
The conversion of human friendly program writing to machine code
Translator
A program to convert high-level or assembly level command into machine code
Assembler
Software that translates an assembly language program into machine code
Assembly language
- processor specific
- translated using an assembler
- One statement translates into one machine code instruction
Source code
The program written by the programmer in a high-level language before it is converted to machine code
Object code
The machine code produced by a compiler
Compiler
Convert all the source code into object code before the program can be run
Advantages of compiling code
- compiled code runs faster
- can be run multiple times without re-translating
- shows all errors at the end
- can produce an executable file
Disadvantages of compiling code
- when you are developing the code it has to be compiled in full
- You can’t try out individual commands
- A compounded program is specific to a particular processor, and it won’t run on a different one
Interpreters
- Convert the source code into machine code one line at a time, and then immediately execute it
- If there is a problem with the source code, the program stops and has to debug the code
- The program needs to be interpreted every time it runs
Advantages of interpretation
- easier to debug
- Errors are picked up at the time of translation
- It is easy to experiment and try different approaches, no need to re compile to try each change
Disadvantages of interpretation
- Code runs slower than compiled code, as translation and execution take place for each line of code
- The code doesn’t get optimised
- The source code must be made available to the customer so it could be adapted or copied
- The user must have a copy of the interpreter resident in memory, occupying more storage
Editors
Software that provide a platform to write code, usually offering a range of tools that make programming easier
Editor use
- Allows the user to enter new program, save, and edit an existing program
- Find and replace all occurrences of text typed in by user
- Auto-indent statements
- Auto-complete statements
- Colour code keywords and common statements
Error Diagnostics
- allows the programmer to find and fix errors
- Allows the programmer to run the code from this point one line at a time
IDE
Integrated development environment- provides all of the tools that are programmer needs to write and test programs in one place
