6, 7, 8. Programs

Question 1

What happens in syntax analysis (2)

Answer 1

• Each statement is checked against the assembler’s rules of syntax
• Parsing happens

Question 2

What is parsing

Answer 2

Systematically breaking down tokens(/statements) into their (grammatical/syntax) component parts e.g. variable to check their syntax is correct

Question 3

What happens in semantic analysis (3)

Answer 3

• Variables are checked to ensure they are the correct data type
• Variables are checked to ensure they’ve been properly declared
• Operations are checked that they are legal for the data type used (you can’t divide a string)

Question 4

What is optimisation

Answer 4

Attempting to reduce the program’s execution time

Question 5

Linking error definition

Answer 5

When a function/library can’t be found

Question 6

Run-time error definition

Answer 6

Occurs when program is run - program is asked to do something it can’t, making it crash (e.g. saving something in a file that hasn’t been created)

Question 7

Interpreter definition

Answer 7

A program that analyses the source code line by line and converts it into machine code (line by line)

Question 8

Can the program run without the interpreter (when it’s being used)?

Answer 8

The program can only run if the interpreter is present

Question 9

Interpreter advantages

Answer 9

✅allows for easier program development - errors can be corrected as program is interpreted
✅lines of code can be modified as its run

Question 10

5 stages of compilation

Answer 10

1 lexical analysis
2 syntax analysis
3 semantic analysis
4 code generation
5 optimisation

Question 11

What happens in lexical analysis (3)

Answer 11

➡️ all comments and spaces are removed
➡️all keywords, Constants and identifiers are replaced by tokens
➡️a symbol table is created with holds the addresses of variables, labels and subroutines

Question 12

Assembler definition

Answer 12

A program that converts low-level language programs (e.g assembly language) into executable code

Question 13

How does an assembler work

Answer 13

Each mnemonic is replaced by the corresponding binary machine code instruction

Question 14

Compiler definition

Answer 14

A program that translates a complete program written in a high level language (source code) into machine code in one go

Question 15

How does a compiler work (3)

Answer 15

Each high level language instruction is converted into many low level ones
The compiled program can be loaded into memory and can run independently from the compiler
List of errors produced at the end

Question 16

Advantages of a compiler

Answer 16

Compiled program runs faster than interpreted program. It checks all lines of code not just the ones being executed

Question 17

Trace role

Answer 17

Displays order in which line of a program are executed and the values of variables as the program is running

Question 18

Break point role

Answer 18

Interrupts a program at a specific line allowing programmer to check a variables current value against expected value

Question 19

Variable watch role

Answer 19

Displays current value of any variable

Question 20

Single stepping

Answer 20

Allows code to be executed line-by-line, the programmer deciding when to move on so they can examine the program carefully as its run

Question 21

Memory inspector

Answer 21

Displays contents of a specific section of memory

Question 22

Error diagnostics role

Answer 22

Displays error messages- helps programmer understand what’s wrong

Question 23

IDE definition

Answer 23

Integrated development environment
Software to help with software engineering by providing tools to do so

Question 24

Editor role

Answer 24

Allows programmer to enter and edit source code and design an interface

Question 25

Compiler definition

Answer 25

Converts source code into machine code. Once compiled, can run multiple times

Question 26

Interpreter role

Answer 26

Converts each line of code into machine code and executes it as it goes- performs each time code is run

Question 27

Linker role

Answer 27

Allows sections of code (functions etc) to be linked together

Question 28

Loader role

Answer 28

Loads previously compiled machine code into memory

Question 29

High level language definition

Answer 29

Resembles human language
Allows use of powerful commands that perform complex tasks- functions

Question 30

High level language advantages

Answer 30

Easier to understand, learn and program
can be run on different programs
Commands can be meaningful and complex

Question 31

Low level language definition

Answer 31

Machine oriented, made of bit patterns that can be directly executed by CPU

Question 32

Low level language advantages

Answer 32

Very fast, minimum amount of storage storage needed

Question 33

Lowest level of low level language

Answer 33

Machine code