 | This article needs additional citations for verification .(June 2022) |
 | This article is missing information about the use of the static keyword to declare class methods in C++ and Java.(April 2014) |
In programming languages such as C, C++, Objective-C, and Java, static is a reserved word controlling both lifetime (as a static variable) and visibility (depending on linkage ). The effect of the keyword varies depending on the details of the specific programming language.
In C and C++, the effect of the static keyword depends on where the declaration occurs.
static may act as a storage class (not to be confused with classes in object-oriented programming), as can extern , auto and register (which are also reserved words). Every variable and function has one of these storage classes; if a declaration does not specify the storage class, a context-dependent default is used:
extern for all top-level declarations in a source file,auto for variables declared in function bodies.| Storage class | Lifetime | Visibility |
|---|---|---|
extern | program execution | external (whole program) |
static | program execution | internal (translation unit only) |
auto, register | function execution | (none) |
In these languages, the term "static variable" has two meanings which are easy to confuse:
static.Variables with storage class extern, which include variables declared at top level without an explicit storage class, are static in the first meaning but not the second.
A variable declared as static at the top level of a source file (outside any function definitions) is only visible throughout that file ("file scope", also known as "internal linkage"). In this usage, the keyword static is known as an "access specifier".
Similarly, a static function –a function declared as static at the top level of a source file (outside any class definitions) –is only visible throughout that file ("file scope", also known as "internal linkage").
Variables declared as static inside a function are statically allocated, thus keep their memory location throughout all program execution, while having the same scope of visibility as automatic local variables (auto and register), meaning they remain local to the function. Hence whatever values the function puts into its static local variables during one call will still be present when the function is called again.
In C++, member variables declared as static inside class definitions are class variables (shared between all class instances, as opposed to instance variables).
Similarly, a static member function –a member function declared as static inside a class definition –is meant to be relevant to all instances of a class rather than any specific instance. A member function declared as static can be called without instantiating the class.
This keyword static means that this method is now a class method; it will be called through class name rather than through an object.
A static method is normally called as <classname>.methodname(), whereas an instance method is normally called as <objectname>.methodname().
In computer programming, the scope of a name binding is the part of a program where the name binding is valid; that is, where the name can be used to refer to the entity. In other parts of the program, the name may refer to a different entity, or to nothing at all. Scope helps prevent name collisions by allowing the same name to refer to different objects – as long as the names have separate scopes. The scope of a name binding is also known as the visibility of an entity, particularly in older or more technical literature—this is in relation to the referenced entity, not the referencing name.
In software systems, encapsulation refers to the bundling of data with the mechanisms or methods that operate on the data. It may also refer to the limiting of direct access to some of that data, such as an object's components. Essentially, encapsulation prevents external code from being concerned with the internal workings of an object.
In computer programming, a global variable is a variable with global scope, meaning that it is visible throughout the program, unless shadowed. The set of all global variables is known as the global environment or global state. In compiled languages, global variables are generally static variables, whose extent (lifetime) is the entire runtime of the program, though in interpreted languages, global variables are generally dynamically allocated when declared, since they are not known ahead of time.
In the C and C++ programming languages, an inline function is one qualified with the keyword inline; this serves two purposes:
register storage class specifier, which similarly provides an optimization hint.inline is to change linkage behavior; the details of this are complicated. This is necessary due to the C/C++ separate compilation + linkage model, specifically because the definition (body) of the function must be duplicated in all translation units where it is used, to allow inlining during compiling, which, if the function has external linkage, causes a collision during linking. C and C++ resolve this in different ways.
The syntax of the C programming language is the set of rules governing writing of software in C. It is designed to allow for programs that are extremely terse, have a close relationship with the resulting object code, and yet provide relatively high-level data abstraction. C was the first widely successful high-level language for portable operating-system development.
The syntax of Java is the set of rules defining how a Java program is written and interpreted.
In computer programming, a static variable is a variable that has been allocated "statically", meaning that its lifetime is the entire run of the program. This is in contrast to shorter-lived automatic variables, whose storage is stack allocated and deallocated on the call stack; and in contrast to objects, whose storage is dynamically allocated and deallocated in heap memory.
In computer science, a local variable is a variable that is given local scope. A local variable reference in the function or block in which it is declared overrides the same variable name in the larger scope. In programming languages with only two levels of visibility, local variables are contrasted with global variables. On the other hand, many ALGOL-derived languages allow any number of nested levels of visibility, with private variables, functions, constants and types hidden within them, either by nested blocks or nested functions. Local variables are fundamental to procedural programming, and more generally modular programming: variables of local scope are used to avoid issues with side-effects that can occur with global variables.
In computer programming, an automatic variable is a local variable which is allocated and deallocated automatically when program flow enters and leaves the variable's scope. The scope is the lexical context, particularly the function or block in which a variable is defined. Local data is typically invisible outside the function or lexical context where it is defined. Local data is also invisible and inaccessible to a called function, but is not deallocated, coming back in scope as the execution thread returns to the caller.
In computer programming, a forward declaration is a declaration of an identifier for which the programmer has not yet given a complete definition.
In computer programming, a declaration is a language construct specifying identifier properties: it declares a word's (identifier's) meaning. Declarations are most commonly used for functions, variables, constants, and classes, but can also be used for other entities such as enumerations and type definitions. Beyond the name and the kind of entity, declarations typically specify the data type, or the type signature ; types may also include dimensions, such as for arrays. A declaration is used to announce the existence of the entity to the compiler; this is important in those strongly typed languages that require functions, variables, and constants, and their types to be specified with a declaration before use, and is used in forward declaration. The term "declaration" is frequently contrasted with the term "definition", but meaning and usage varies significantly between languages; see below.
The C and C++ programming languages are closely related but have many significant differences. C++ began as a fork of an early, pre-standardized C, and was designed to be mostly source-and-link compatible with C compilers of the time. Due to this, development tools for the two languages are often integrated into a single product, with the programmer able to specify C or C++ as their source language.
C++11 is a version of the ISO/IEC 14882 standard for the C++ programming language. C++11 replaced the prior version of the C++ standard, called C++03, and was later replaced by C++14. The name follows the tradition of naming language versions by the publication year of the specification, though it was formerly named C++0x because it was expected to be published before 2010.
In the C programming language, an external variable is a variable defined outside any function block. On the other hand, a local (automatic) variable is a variable defined inside a function block.
As an alternative to automatic variables, it is possible to define variables that are external to all functions, that is, variables that can be accessed by name by any function. Because external variables are globally accessible, they can be used instead of argument lists to communicate data between functions. Furthermore, because external variables remain in existence permanently, rather than appearing and disappearing as functions are called and exited, they retain their values even after the functions that set them have returned.
In programming languages, particularly the compiled ones like C, C++, and D, linkage describes how names can or can not refer to the same entity throughout the whole program or one single translation unit.
This article describes the syntax of the C# programming language. The features described are compatible with .NET Framework and Mono.
This comparison of programming languages compares how object-oriented programming languages such as C++, Java, Smalltalk, Object Pascal, Perl, Python, and others manipulate data structures.
In computer programming, a constant is a value that is not altered by the program during normal execution, i.e., the value is constant. When associated with an identifier, a constant is said to be "named," although the terms "constant" and "named constant" are often used interchangeably. This is contrasted with a variable, which is an identifier with a value that can be changed during normal execution, i.e., the value is variable.
In programming languages, name resolution is the resolution of the tokens within program expressions to the intended program components.