Program construction

Question 1

assembler

Answer 1

translates code from low level assembly language to machine code
once assembled program file can be re-used without assembly

Question 2

interpreter

Answer 2

reads, translates and executes one line at a time from high level language program

Question 3

interpreter pros

Answer 3

will stop when comes across a line with an error which makes debugging easier

Question 4

interpreter cons

Answer 4

doesn’t produce executable file so must be re-translated each run - slower overall
relevant interpreter to source code must be installed

Question 5

compiler

Answer 5

translates code from high level to machine all at once then executes used by C++

Question 6

compiler pros

Answer 6

slow for first run though due to translation but produces executable file that means only needs to be translated once

Question 7

compiler cons

Answer 7

can produce multiple errors at same time so hard to debug
if needs to run on diff platform it will need to be recompiled to be targeted at required platformst

Question 8

stages of the compilation process

Answer 8

lexical analysis
syntax analysis
semantic analysis
code generation and optimiser

Question 9

lexical analysis

Answer 9

comments and unneeded spaces are removed
converts source code into token stream and puts them into the symbol table
keywords, constants and identifiers become tokens (usually hex numbers) in the table

Question 10

syntax analysis

Answer 10

the tokens are checked to see if they match the expected spelling and grammar
done by parsing each token to determine if it uses the correct syntax for the language
produces error message if syntax error found

Question 11

semantic analysis

Answer 11

variables checked to ensure:
they have been properly declared and used + they are of the correct data type
operations checked to ensure they are legal for data type being used

Question 12

code generation

Answer 12

code specific to target machine is generated
several lines of machine code for each high level instruction

Question 13

code optimisation

Answer 13

replacement of inefficient code done by compilers to increase speed of the program, decrease demand on resources while still achieving desired output and not delaying overall compilation process