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A-level Computer Science > SLR 15 - programming languages and translators > Flashcards

SLR 15 - programming languages and translators Flashcards

1
Q

What is the difference between how programs that have been compiled and programs that have been interpreted can run?

A

Compiled programs can be run without requirement for any other software to be present. This is not the case with interpreters

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2
Q

How do interpreters work?

A
  • They have procedures that can be used to translate each kind of program instruction
  • They check for errors as they translate rather than before
  • A program with errors with be partially translated until the error is reached
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3
Q

How is bytecode executed?

A
  • With a virtual machine which can execute bytecode of different processors
  • Each different processor instruction set will have its own virtual machine
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4
Q

Why do we need translators?

A

A program needs to be in machine code to be executed, so translators are needed to convert HLL and Assembly language into machine code (binary)

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5
Q

What are the 3 types of translator?

A
  • assembler
  • interpreter
  • compiler
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6
Q

What does an assembler do?

A

It converts assembly language into machine code

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7
Q

Why is assembly language translation quick and easy?

A
  • an assembly language instruction has a one to one relationship with machine code
  • this means translation is quick
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8
Q

Why do different assembler need to exist for each different type of processor instruction set?

A

They are platform specific

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9
Q

What do compilers do?

A

They translate programs written in high-level languages into machine code

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10
Q

How do compilers work?

A
  • They take the HLL as their source code
  • They check it for any errors
  • Then translate the whole program at once
  • If there is an error the source code then it will not be translated
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11
Q

Why are compilers deemed platform specific?

A

They produce machine code

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12
Q

What do interpreters do?

A
  • they translate HLL into machine code LINE BY LINE
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13
Q

Why do interpreters offer poor protection for their source code?

A
  • during translation, the program source code and the interpreter must be present
  • it makes the original code difficult to extract
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14
Q

Advantages of interpreters?

A
  • useful when writing programs
  • no need for lengthy, time consuming recompilation every time an error is found
  • makes it much easier to partially test and debug programs
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15
Q

Advantages of compilers?

A
  • Generated object code is kept on a disk, it can be run when needed without needing to recompile it
  • once created, object code executes much faster then interpreted code
  • the object code is relatively secure, it is hard to read it and work out what the source code would have been (protected from extraction)
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16
Q

What do compilers sometimes produce before machine code? Example?

A

intermediate language e.g., bytecode. its a half-way standard language which can then be translate to computer specific machine code

17
Q

Why do compilers produce intermediate language?

A

it allows for platform independence

18
Q

What is the advantage of intermediate language?

A

It allows the interpreter to translate the source code just once, while still being able to execute the translated code with a variety of different processors

19
Q

What is source code?

A

The name given to the input to a translator e.g., assembly language for an assembler and HHL for compilers and interpreters

20
Q

What is object code?

A

The translators output and is produced from source code

21
Q

Define a quick time-line of computer languages:

A
  • limited speed and memory of computers meant programmers coded in LLL (machine code), which directly manipulated the processor (often difficult and prone to errors)
  • Assembly code
  • Then HHL developed (one to many relationship) where instructions could be communicated to the computer processor
22
Q

What are the characteristics of a LLL?

A
  • they are specific to the type of processor they are written for
  • they directly affect the computer processor
23
Q

What are the two types of low level language?

A
  • machine code
  • assembly code
24
Q

What are the disadvantages of Machine code?

A
  • it uses only binary but its very long and difficult for humans to understand
  • Machine code programs are prone to errors
  • Very difficult to debug
25
Q

What are the advantages of Machine code?

A
  • it directly manipulates a computer’s processor so it a powerful paradigm
  • you’re never limited programming in machine code
  • no ned for translation so useful when working with embedded systems and real time applications
26
Q

Why was assembly language created?

A
  • it simplified machine code by using mnemonics like ADD and MOV
  • it made programming ore compact and less error prone
27
Q

Why was assembly language still quickly processed?

A

the language instruction has a one to one correlation to a machine code instruction

28
Q

What is the difference between HHL and LLL?

A
  • HHL are not processor specific
  • HHL must be translated into machine code before they can be executed
  • HHL lets programmers use built in functions
  • Easier to debug due to named variables, indentation etc
29
Q

What are the two types of HLL?

A
  • interpretive
  • declarative
30
Q

What is an imperative HLL?

A
  • are formed from instructions that specify how the computer should complete a task
  • code executed one line at a time e.g. C# and Java
31
Q

What is an declarative HLL?

A
  • describes what a computer should do
  • SQL?
32
Q

Machine code:
- portability?
- ease of use?
- ease of debugging?
- ease of execution?

A
  • Not portable
  • Code is difficult for humans to understand
  • Errors are very difficult to spot and correct.
  • Machine code is directly executed by processors.
33
Q

Assembly Language:
- portability?
- ease of use?
- ease of debugging?
- ease of execution?

A
  • Programs are processor specific
  • Mnemonics help to make code slightly easier for humans to understand
  • Debugging is easier than with machine code but still far more difficult than with high-level languages
  • An assembler must be used before a program is executed, but each instruction has a 1-to-1 correlation to a machine code instruction so translation is quick.
34
Q

High Level Language:
- portability?
- ease of use?
- ease of debugging?
- ease of execution?

A
  • Portable. Programs are not specific to certain processors.
  • Code uses English, making it easy for humans to understand.
  • Named variables, indentation and commenting make debugging fairly easy
  • A compiler or interpreter must be used to translate source code into object code before it can be executed. This can be time consuming.
35
Q

What is intermediate code designed to run on?

A

A virtual machine installed on each make of computer

A-level Computer Science (11 decks)

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