The definition and general characteristics of programming language

1. Definition of program language

　The programming language is a notation System. There are two characteristics of the marking system:

Grammar: a set of rules of a language used to form and generate programs

Semantics: the meaning of a language used to denote the logical relationship of a program

2. Some syntax-related definitions

　　Alphabet: a non-empty finite set of elements, recorded as ∑. For Example: ∑={a,b}

Symbols: elements in an alphabet are called symbols

Symbol string: A poor sequence of symbols, for example: a,aa,aaa,ac,aaccc,.., symbol string without any symbols is called an empty symbol string and is recorded as ε

Symbol string Length: the number of symbols in the symbol string, if there is x=sss, then the length of X is |x|=3,|ε|=;

Symbolic string connection: If x, y is defined on the ∑ of the symbol string, it is called xy x and y connection, xy is also ∑ on the symbol string, εx=x=xε;

Positive closures for the collection of symbolic strings: a+=a1∪a2∪a3∪ ... ∪an ...

Reflexive closure of a collection of symbolic strings: a*={ε}∪a+

　　

The definition and general characteristics of programming language