Chapter 10 - Programming language translators

Question 1

What type of code is needed for the CPU to understand it and execute the instructions?

Answer 1

» Machine code

Question 2

What is the relationship between assembly code and a binary code instruction?

Answer 2

» One - to -one

Question 3

What does the machine code instructions that a particular computer can execute depend on?

Answer 3

» The instruction set

Question 4

What is the processor instruction set?

Answer 4

» Manufacturer defines a set of these instructions that processor will be able to carry out that will only work with that particular processor
» Each type of processor will have a different instruction set and different assembly code

Question 5

What are 2 features of low level language?

Answer 5

» Specific to the instruction set of the processor
» Non-portable (Meaning it can only be run on a processor of the same type that it was written for)

Question 6

What is an advantage of using low level languages?

Answer 6

» Can make use of specific registers
» Therfore programmers have greater control over the movement of data in and out of the processor

Question 7

Why are low-level languages not portable?

Answer 7

» As the machine code and assembly code are designed for that specific processor
» Therefore cannot be processed on other processors

Question 8

What are 2 disadvantages of using low level languages?

Answer 8

» Difficult to write programs in low level languages as programmers need to have a very good understanding of the hardware being used
» Do not have libraries

Question 9

What are the categories of low level language?

Answer 9

» Assembly code
» Machine code

Question 10

What is the source code?

Answer 10

» Programming statements that are created by a programmer

Question 11

What are 2 features of assembly code?

Answer 11

» Type of low-level-language, which is made up of commands/mnemonics
» Each code translates into 1 machine code instruction

Question 12

What are the advantages of high-level languages?

Answer 12

» Much easier to write/read words
» Portable
» Come with libraries

Question 13

How are assembly code instructions translated into machine code?

4 marks

Answer 13

» Done by an assembler
» Replaces mnemonic opcodes with machine code - LDA
» Replaces numeric operands with machine code - NUM2
» Chekcs syntax and runs error diagnostics if erros is found

Question 14

What does the compiler do?

Answer 14

» Translates whole program written in a high level language into executable machine code
» Creates object code before being executed into machine code

Question 15

How does a compiler work?

Answer 15

» Translates high-level code into machine all at once
» Carrying out a number of checks first
» Compiled code is non-portable
» Code can be run without a translater being present

Question 16

What does an interpreter do?

Answer 16

» Translate code from high level language into machine code line by line

Question 17

What are the advantages of a compiler?

Answer 17

» Code can be optimised by the compilier
» Can be distributed as machine code,meaning that the source code is hiddent

Question 18

What are the disavantages of a compiler?

Answer 18

» You have to wait until the entire program is compiled before receiving any errors - may take a large time for a large program
» Executable code is non-portable

Question 19

What are the benefits of an interpreter?

Answer 19

» Errors will be reported as soon as they are ecountered - dont have to wait for the entire program to be compiled
» Debugging is quick and easily

Question 20

What are the drawbacks of an interpreter?

Answer 20

» Program requires an interpreter to be run
» The interpreter takes up space in memory

Question 21

What is object code?

Answer 21

» Halway code between high level and machine code
» Set of instruction codes that is understood by a computer at the lowest hardware level, but not ready to be executed by the CPU

Question 22

What is the difference between a compiler and an interpreter in terms of the steps to turn code in machine code?

Answer 22

» Compiler - Source code - Object code - Machine code
» Interpreter - Source code - Machince code

Question 23

What are 2 differences between a compiler and an interpreter?

Answer 23

» Compiler does produce object code - interpreter does not
» Compiler translates the whole source code at once, intepreter analyses the code line by kine

Question 24

What is a library, and give an example?

Answer 24

» Sections of code already pre-programmed by other developers containg useful routines
» Such as RANDOM

Question 25

What are 3 advantages of using libraries?

Answer 25

» Saves time » Uses expertise of other » Has been already tested, making debugging easier

Question 26

What are 2 disadvantages of using libraries?

Answer 26

» May increase size of compiled file as library contains many routines that aren't being used » Not written by the programmer - may need to spend time familarising themsleves with it

Question 27

What is the purpose of the linker?

Answer 27

» Links the main program to libaries by including them in the final executable code

Question 28

What is the loader?

Answer 28

» Part of the OS which is then responsible for loading a program into main memory

Question 29

What are the 4 stages of compilation?

Answer 29

» Lexical analysis » Syntax analysis » Code generation » Code optimisation

Question 30

What is a helpful mneumonic to help remember the stages of compliation

Answer 30

» Life Sucks G.O

Question 31

What are 3 features of lexical analysis?

Answer 31

» All unnecessary spaces (whitespaces) and all comments are removed » Keywords, (e.g print), constants and identifiers are replaced with tokens - represents their function in the program » A symbol table for every keyword and identifier in the program is developed

Question 32

What are some examples of tokens?

Answer 32

» <.identifier>,<.operator>,<.number>,<.keyword>,<.open_bracket>,<.close_bracket> » Note the dot is needed, it is just their because of brainscape syntaxing lol

Question 33

What ar 4 features of Syntax Anaylsis?

Answer 33

» Tokens from Lexical Analysis are checked against the rules of the language » Errors reported with a list of diagnositics » Detail is added to the Abstract Syntax Tree » Passes to code generation

Question 34

What are 3 features of Code generation?

Answer 34

» Here object code is created » Program called linker can incorporate the code from libary with the main program » Into a single executable file

Question 35

What are 3 features of code optimisation?

Answer 35

» Removes redundant instructions » Replace inefficient code with code that achieves the same result but in a more effiecient way » Allows code to execute faster - decrease memory usage

Question 36

What are 3 features of code optimisation?

Answer 36

» Removes redundant instructions » Replace inefficient code with code that achieves the same result but in a more effiecient way » Allows code to execute faster - decrease memory usage

Question 37

Why is Lexical analysis needed?

Answer 37

» Necessary to put the code into a format which can be read/processed by the syntax analyser

Question 38

Why is syntax analysis needed?

Answer 38

» To ensure the code is valid in as much as it meets all the structural rules of the language. Guarentees it runs

Question 39

Why is Code Generation needed?

Answer 39

» Turn the code into a format that processor can understand

Question 40

Why is code optimisation needed?

Answer 40

» Ensures the code runs much quicker and uses less memory