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An identifier is the name of an element in the code. There are certain standard naming conventions to follow when selecting names for elements. Identifiers in Java are case-sensitive. An identifier can contain: Any Unicode character that is a letter (including numeric letters like Roman numerals) or digit. Currency sign (such as ¥).
A global identifier is declared outside of functions and is available throughout the program. A local identifier is declared within a specific function and only available within that function. [1] For implementations of programming languages that are using a compiler, identifiers are often only compile time entities.
A snippet of Java code with keywords highlighted in blue and bold font. In the Java programming language, a keyword is any one of 68 reserved words [1] that have a predefined meaning in the language. Because of this, programmers cannot use keywords in some contexts, such as names for variables, methods, classes, or as any other identifier. [2]
longer identifiers may be disfavored because of visual clutter; It is an open research issue whether some programmers prefer shorter identifiers because they are easier to type, or think up, than longer identifiers, or because in many situations a longer identifier simply clutters the visible code and provides no perceived additional benefit.
Code from other packages is accessed by prefixing the package name before the appropriate identifier, for example class String in package java.lang can be referred to as java.lang.String (this is known as the fully qualified class name). Like C++, Java offers a construct that makes it unnecessary to type the package name (import).
For example, "Identifier" can be represented with 0, "Assignment operator" with 1, "Addition operator" with 2, etc. Tokens are often defined by regular expressions , which are understood by a lexical analyzer generator such as lex , or handcoded equivalent finite-state automata .
A notable example is in Java, where const and goto are reserved words — they have no meaning in Java but they also cannot be used as identifiers. By reserving the terms, they can be implemented in future versions of Java, if desired, without breaking older Java source code.
Some programming languages are case-sensitive for their identifiers (C, C++, Java, C#, Verilog, [2] Ruby, [3] Python and Swift).Others are case-insensitive (i.e., not case-sensitive), such as ABAP, Ada, most BASICs (an exception being BBC BASIC), Common Lisp, Fortran, SQL (for the syntax, and for some vendor implementations, e.g. Microsoft SQL Server, the data itself) [NB 2] Pascal, Rexx and ...