The Function and Purpose of Translators Flashcards
Define assembly language.
A low level language that uses mnemonics and labels to represent a full set of instructions.
What is the assembler?
A piece of software that translates assembly language into machine code.
The assembler must be machine specific.
Define high level language.
A high level language written as source code. It is understandable by the programmer often using keywords to represent instructions.
Define machine code.
- binary notation/executable form
- set of all instructions available
- (instructions operate on) bytes of data
- dependent on architecture/processor design
What is an interpreter?
A translator program that translates source code one line at a time into machine code.
What is an interpreter useful for and why?
Debugging and testing as it returns accurate error messages as they arrive.
What is a compiler?
A translator program that translates the source code as a unit into machine code to produce an executable program file.
What is the purpose of intermediate code?
- It can run on a variety of machines using an interpreter
- Improves portability
- Allows sections of programs to be written in different languages
- Used in a virtual machine
What additional software is needed to run the intermediate code?
An interpreter/ Virtual Machine
What is the main purpose of a translator?
- To translate source code into object code
- To detect and report any errors
What are the disadvantages of using intermediate code?
- program runs more slowly
- has to be translated each time program is run
- needs additional software
What does optimisation do?
- make code as efficient as possible
- increases processing speed
- reduces the number of instructions
What are the features of an interpreter?
- translates one line at a time
- runs each line before translation of next
- reports one error at a time and then stops
- indicates the position of the error
What are the disadvantages of using an interpreter?
- Program runs more slowly due to translation each time
- Additional software is needed every time the program is run
What are the advantages of using a compiler?
- Protects programs from malicious use
- Optimisation improves program speed
- Compiler is no longer needed once executable file is produced.
Describe the steps an assembler performs when producing machine code.
- reserves storage for instructions & data
- replaces mnemonic opcodes by machine codes
- replaces symbolic addresses by numeric addresses
- creates symbol table…
- …to match labels & addresses
- checks syntax/gives error diagnostics
Why are library routines used?
- to perform common tasks
- they are error-free/have been tested
- ready to use/saves work/saves time
- may be used multiple times
- may have been written in different source language
- use other programmers’ expertise
What are the stages of compilation?
- syntax analysis
- lexical analysis
- code generation
What happens during syntax analysis?
- accepts output from lexical analysis
- statements/arithmetic expressions/tokens are checked…
- …against the rules of the language/valid example given eg matching brackets
- errors are reported as a list (at the end of compilation)
- diagnostics may be given
- (if no errors) code is passed to code generation
- further detail is added to the symbol table…
- …eg data type /scope/address
Explain the term intermediate code and its use.
- simplified code / partly translated code…
- …which can be run on any computer/virtual machine/improves portability…
- …using an interpreter
- sections of program can be written in different languages
- runs more slowly than executable code
What software is used to convert source code into object code?
translator
Explain the term source code.
- the original code/code written by the programmer…
- …often in a high level language
- may be in assembly language
- source code can be understood by people…
- …but cannot be executed (until translated)
What is a library routine?
- routines are pieces of software…
- …which perform common tasks…
- …such as sorting/searching
- routines are compiled
How are library routines used?
- linker is used…
- …to link routine with program
- loader handles addresses…
- …when program is to be run
Describe code generation.
- Occurs after syntax analysis/is last phase of
compilation - Produces machine code program/executable
code/intermediate code… - …which is equivalent to the source program
- Variables/constants are given addresses
- Relative addresses are calculated.
Describe optimisation.
- Makes code as efficient as possible
- Increases processing speed
- Number of instructions is reduced
