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The null data type represents a variable that has no value. The only value in the null data type is NULL. The NULL constant is not case sensitive. [30] Variables of the "resource" type represent references to resources from external sources. These are typically created by functions from a particular extension, and can only be processed by ...
In compilers, live variable analysis (or simply liveness analysis) is a classic data-flow analysis to calculate the variables that are live at each point in the program. A variable is live at some point if it holds a value that may be needed in the future, or equivalently if its value may be read before the next time the variable is written to.
In computer science, control flow (or flow of control) is the order in which individual statements, instructions or function calls of an imperative program are executed or evaluated. The emphasis on explicit control flow distinguishes an imperative programming language from a declarative programming language.
A canonical example of a data-flow analysis is reaching definitions. A simple way to perform data-flow analysis of programs is to set up data-flow equations for each node of the control-flow graph and solve them by repeatedly calculating the output from the input locally at each node until the whole system stabilizes, i.e., it reaches a fixpoint.
[5] [6] [7] A line comment ends at the end of the text line. In modern languages, a line comment starts with a delimiter but some older languages designate a column at which subsequent text is considered comment. [7] Many languages support both block and line comments – using different delimiters for each.
Data flow diagram with data storage, data flows, function and interface. A data-flow diagram is a way of representing a flow of data through a process or a system (usually an information system). The DFD also provides information about the outputs and inputs of each entity and the process itself.
As of 21 January 2025 (two months after PHP 8.4's release), PHP is used as the server-side programming language on 75.0% of websites where the language could be determined; PHP 7 is the most used version of the language with 47.1% of websites using PHP being on that version, while 40.6% use PHP 8, 12.2% use PHP 5 and 0.1% use PHP 4.
The program focuses on commands, in line with the von Neumann [2]: p.3 vision of sequential programming, where data is normally "at rest". [3]: p.7 In contrast, dataflow programming emphasizes the movement of data and models programs as a series of connections.