Levels of Programming Languages (OCR GCSE Computer Science): Revision Notes

Levels of Programming Languages

Programming languages are categorised into high-level and low-level languages based on their characteristics and their closeness to machine code.

Low-Level Languages

Low-level languages are closer to machine code, which is the binary code understood by a computer's CPU.

Machine Code

• Description: Binary code that directly controls a CPU's operations.
• Characteristics:
  • Processor-specific (each processor type has its own machine code).
  • Executed directly by the hardware without needing translation.
  • Written in binary (1s and 0s).
• Example:
  • 10101010 could be a binary instruction specific to a CPU.

Assembly Code

• Description: A low-level programming language that uses mnemonics (short abbreviations) to represent machine code.
• Characteristics:
  • Easier to understand than machine code.
  • Processor-specific, just like machine code.
  • Commonly used in embedded systems.
  • Requires an assembler to be converted into machine code.
• Example:
  • LDA (Load), STA (Store) are examples of assembly code instructions.

High-Level Languages

High-level languages are closer to human languages and are abstracted from machine code.

• Description: These languages use commands that resemble structured English and are designed to be easy to read and write for humans.
• Characteristics:
  • Machine-independent (can be used across different systems).
  • Requires a compiler or an interpreter to translate into machine code.
  • Easier to debug and maintain compared to low-level languages.
  • Examples include Python, Java, C++, JavaScript, and C#.

Differences Between High-Level and Low-Level Languages

Feature	Low-Level Languages	High-Level Languages
Closeness to Machine	Very close (binary or mnemonics)	Far from the machine, close to human
Portability	Machine-specific	Portable across different systems
Ease of Understanding	Hard to learn	Easy to understand (resembles English)
Memory Efficiency	More memory efficient	Less memory efficient
Execution Speed	Faster (no need for translation)	Slower (requires translation)
Direct Hardware Access	Can manipulate hardware directly	Limited direct hardware access

Advantages and Disadvantages

Low-Level Languages	High-Level Languages
Advantages	Advantages
Uses less memory	Easier to learn and write
Executes faster	More readable and maintainable
Allows direct control of hardware	More portable across different systems
Disadvantages	Disadvantages
Hard to learn and understand	Slower execution due to the translation
Harder to debug and maintain	Requires more memory
Specific to one machine