High-Level vs Low-Level Languages
Computer Science: OCR GCSE, topic 2.5.1
High-Level Languages
Most computer languages are written in high-level programming languages.
High-Level Languages
- High-level languages (HLLs) include most programming languages such as Python, C++ and Java.
- High-level languages are made of human-readable statements that make it easier for us to program.
- High-level languages are portable, which means that they can be run on many different types of hardware.
What does a HLL look like?
- Commands in a high-level language look very like English. For example:
- print()
- SELECT * FROM users;
Why don't we always use HLLs?
- Computers can only process instructions in the form of binary numbers.
- We use special software called a translator to convert our HLL source code into an executable binary file.
Advantages
- HLLs are quicker to create software because one line of code can perform multiple actions on the CPU.
- A programmer does not have to think about how a program interacts with hardware. They can focus on creative problem-solving.
Low-Level Languages
Low-level programming languages are languages which are much closer to computer-understandable binary.
Low-Level Languages
- Low-level languages (LLLs) are much closer to executable machine code than high-level languages.
- LLLs are harder to read by humans, but are easier to read for the computer.
What does a LLL look like?
- LLL commands are not easy to read, and might include commands such as:
- MOV ax, bx
- CMP ch, dh
- CLI
Why do we use LLLs?
- LLLs provide exact control over the central processing unit.
- LLLs need less translation, and often lead to faster code which is useful for computers with low specifications such as embedded systems.
Comparison
- How would you write a simple addition program using values stored in two variables?
- High-level language
num1 = 17
num2 = 4
print(num1+num2) - Low-level language (Little Man Code)
INP // Input first number
STA A // Store it in mailbox A
INP // Input second number
ADD A // Add the stored first number to the second
OUT // Output the sum
HLT // Stop
A DAT
Test yourself on High-Level vs Low-Level Languages
What does it mean for a language to be portable?
Which of these statements look like high-level language?
Why don't we always use high-level languages?
Which of these look like low-level statements?
Which type of language often have more optimised (faster) code?