Syntax and semantics are concepts that apply to all languages, including programming languages. Programming languages are considered artificial languages, just like natural languages such as English and Mandarin.
Syntax of a Language
- The syntax of a language refers to a set of characters and their acceptable arrangements or sequences.
- In English, for example, the syntax includes the alphabet, punctuation, properly spelled words, and properly punctuated sentences.
- A syntactically correct sentence in English would be: “Hello there, how are you?” An example of a sentence that is not syntactically correct is: “Hello there, hao are you?”
- In this sentence, the sequence of letters “hao” is not a valid word in the English language.
- In Mandarin, the term “Hao” is syntactically correct and translates to “good.”
- Thus, each language has its own syntax and semantics, which define the structure and meaning of the language.
Semantics of a Language
- The semantics of a language deals with the meaning associated with each syntactically correct sequence of characters.
- Semantics determine the interpretation and understanding of language constructs.
- A sentence can be syntactically correct but semantically incorrect, rendering it meaningless.
- For instance, the sentence “Colourless green ideas sleep furiously” is syntactically correct but semantically incorrect, and thus has no meaning.
Program Translation
- The Central Processing Unit (CPU) is designed to interpret and execute a specific set of instructions represented in binary form (i.e., 1s and 0s) called machine code.
- Only programs in machine code can be executed by a CPU.
- Writing programs in machine code is tedious and error prone. Most programs are written in high-level programming languages (e.g., Python)
- Since
high-level programs are not in machine code, they require translation.
- A translator program is
necessary to convert high-level language programs into machine code, as
CPUs can only execute instructions in machine code.
- There are two fundamental types of translators: Complier and Translator
Compiler:
- A compiler translates programs directly into machine code.
- Programs can then be executed by the CPU.
- Compiled programs generally execute faster than interpreted on.
Interpreter:
- An interpreter executes program instructions directly, “running on top of” the CPU.
- It translates and executes instructions immediately as they are entered. This is referred to as interactive mode.
- Python is an example of a language executed by an interpreter.
Compiled
programs typically
have faster execution times compared to interpreted programs. Both compilers and interpreters are
essential depending on the programming language and the specific use
case.