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In computer programming, a static variable is a variable that has been allocated "statically", meaning that its lifetime (or "extent") 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 dynamically allocated objects, whose storage is allocated and deallocated in heap ...
Such data is usually processed using real-time computing although it can also be stored for later or off-line data analysis. Real-time data is not the same as dynamic data. Real-time data can be dynamic (e.g. a variable indicating current location) or static (e.g. a fresh log entry indicating location at a specific time).
Besides the static constants described above, many procedural languages such as Ada and C++ extend the concept of constantness toward global variables that are created at initialization time, local variables that are automatically created at runtime on the stack or in registers, to dynamically allocated memory that is accessed by pointer, and to parameter lists in function headers.
The different types of variables are static, stack-dynamic, explicit heap-dynamic, and implicit heap-dynamic. A static variable is also known as global variable, it is bound to a memory cell before execution begins and remains to the same memory cell until termination. A typical example is the static variables in C and C++.
A const static variable (global variable or static local variable) is a constant, and may be used for data like mathematical constants, such as double const PI = 3.14159 – realistically longer, or overall compile-time parameters. A const automatic variable (non-static local variable) means that single assignment is happening, though a ...
static is a reserved word in many programming languages to modify a declaration. The effect of the keyword varies depending on the details of the specific programming language, most commonly used to modify the lifetime (as a static variable) and visibility (depending on linkage), or to specify a class member instead of an instance member in classes.
Providing a static method that returns a reference to the instance; The instance is usually stored as a private static variable; the instance is created when the variable is initialized, at some point before when the static method is first called. This C++23 implementation is based on the pre-C++98 implementation in the book [citation needed].
Soft real-time systems are typically used to solve issues of concurrent access and the need to keep a number of connected systems up-to-date through changing situations. Some examples of soft real-time systems: Software that maintains and updates the flight plans for commercial airliners. The flight plans must be kept reasonably current, but ...