GCSE Link: 2.16 - Programming Language Classification

Programming languages can be split into two types: high-level and low-level languages

Some examples of high-level languages include Python, Java, Thunno, and Go.

The only low-level languages are assembly language and machine code.
Machine code is written in binary, and is the only form of code that a computer can understand.
Each instruction in assembly language represents one instruction of machine code.

Example 1 (Python) and Example 2 (AQA assembly language) show exactly the same algorithm in different languages.

Example 1
a = int(input())
print(a * a)

Example 2
  LDR R0, #0
  LDR R1, 101
  LDR R2, 101
loop:
  CMP R2, #0
  BEQ end
  ADD R0, R0, R1
  SUB R2, R2, #1
  B loop
end:
  STR R0, 102
  HALT

Advantages of high-level languages:

• As seen in the examples above, high-level languages like Python are often much easier to read and understand than low-level languages like assembly language and machine code.
• The same code in a high-level language will work on any processor, whereas code in low-level languages is dependent on the processor type.
• Because each line of code in a high-level language can represent multiple instructions in machine code, high-level languages are usually easier and quicker to program in than low-level languages.

Advantages of low-level languages:

• Commands in machine code can be executed directly, without the need for a translator (2B.08).
• Low-level languages have more control over the hardware (e.g. you can control exactly how memory is used in the program).
• Very efficient code can be written for a particular type of processor, so programs in low-level languages generally execute faster and use less memory than programs in high-level languages.

Only machine code can be understood by the computer. Everything else has to be translated (converted) into machine code.

Translators are a type of software which translate (convert) code into machine code that the computer can run.

There are three types of translator: compilers, interpreters, and assemblers.
Compilers and interpreters work on high-level languages. Assemblers work on assembly language.

Compilers translate a whole program directly into machine code, while interpreters translate one line at a time, calling machine code subroutines to execute the file.

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What are the advantages and disadvantages of compiled languages as opposed to interpreted languages?

Advantages:
• Compilation results in an executable machine code file which will run more quickly than interpreted code
• The original source code cannot be retrieved once compiled, which is good for mass distribution (e.g. games)
• The file can be run directly without any other software

Disadvantages:
• Compilation can take a long time for larger projects
• The executable file is specific to a processor type and will not run on devices with other processors

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