process of compilation

Question 1

name the stages of compilation in order

Answer 1

lexical analysis
syntax analysis
semantic analysis
code generation
optimisation

Question 2

What does the Lexical analysis stage remove?

Answer 2

comments and spaces

Question 3

What is replaced with tokens in this lexical analysis stage?

Answer 3

keywords, constants and identifiers in the source code

Question 4

What is created in lexical analysis stage?

Answer 4

symbol table- holds the addresses of variables, labels and subroutines

Question 5

What’s the function of the syntax analysis stage?

Answer 5

Each statement is checked against the rules of syntax for the assembler

Question 6

What’s checked in syntax analysis?

Answer 6

spelling

grammar

sequence of input characters, symbols, items or tokens should obey the rules of syntax of the language

Question 7

Describe parsing.

Answer 7

task of systematically breaking down high level statements into their component parts e.g. reserved words and variables

during translation process

Question 8

What does the semantic analysis stage do?

Answer 8

check meanings of statements are clear and consistent with rules of compiler, structure and data types that are supposed to be used

checks to see if all variables in program have been declared

carries out type checks e.g. makes sure real values haven’t been assigned to integer variables

checks that appropriate operations have been carried out on variables e.g. integer division not carried out on real variables

Question 9

What does the code generation stage do?

Answer 9

generates machine code

high level statements (most) translated into several machine code instructions

Question 10

What is optimisation stage?

Answer 10

employing a technique to try and reduce the execution time of the object program

Question 11

Explain a syntax error.

Answer 11

occurs when program is being compiled

code doesn’t fit into expected syntax of the language

e.g. spelling mistake, not closing brackets, missing colon

Question 12

Explain linking error.

Answer 12

may occur if compiled program is linked to library routines

e.g. a program may not be present in the library

Question 13

Explain run time error.

Answer 13

occurs when program is being run

parts of program work, elements have been coded incorrectly

program will crash (this is a run time error)

e.g. a program tries to display a user’s name but the name hasn’t been saved anywhere and so the program crashes

Question 14

Explain rounding error.

Answer 14

When a number is approximated to the nearest whole number

Question 15

Explain logical error.

Answer 15

causes a program to output an incorrect value, but the program doesn’t crash

Question 16

Explain a truncation error.

Answer 16

where a number is approximated to a whole number/tenth/hundredth etc nearer to zero