Memory management unitA memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit that examines all memory references on the memory bus, translating these requests, known as virtual memory addresses, into physical addresses in main memory. In modern systems, programs generally have addresses that access the theoretical maximum memory of the computer architecture, 32 or 64 bits. The MMU maps the addresses from each program into separate areas in physical memory, which is generally much smaller than the theoretical maximum.
Object compositionIn computer science, object composition and object aggregation are closely related ways to combine objects or data types into more complex ones. In conversation the distinction between composition and aggregation is often ignored. Common kinds of compositions are objects used in object-oriented programming, tagged unions, sets, sequences, and various graph structures. Object compositions relate to, but are not the same as, data structures.
Programming idiomIn computer programming, a programming idiom or code idiom is a group of code fragments sharing an equivalent semantic role, which recurs frequently across software projects often expressing a special feature of a recurring construct in one or more programming languages or libraries. This definition is rooted in the definition of "idiom" as used in the field of linguistics. Developers recognize programming idioms by associating meaning (semantic role) to one or more syntactical expressions within code snippets (code fragments).
Second-generation programming languageThe label of second-generation programming language (2GL) is a generational way to categorize assembly languages. The term was coined to provide a distinction from higher level machine independent third-generation programming languages (3GLs) (such as COBOL, C, or JavaScript) and earlier first-generation programming languages (machine code) Second-generation programming languages have the following properties: Lines within a program correspond directly to processor commands, essentially acting as a mnemonic device overlaying a first generation programming language.
Coding best practicesCoding best practices or programming best practices are a set of informal rules (best practices) that many software developers in computer programming follow to improve software quality. Many computer programs remain in use for long periods of time, so any rules need to facilitate both initial development and subsequent maintenance and enhancement of source code by people other than the original authors. In the ninety-ninety rule, Tom Cargill is credited with an explanation as to why programming projects often run late: "The first 90% of the code accounts for the first 90% of the development time.
Szymański's algorithmSzymański's Mutual Exclusion Algorithm is a mutual exclusion algorithm devised by computer scientist Dr. Bolesław Szymański, which has many favorable properties including linear wait, and which extension solved the open problem posted by Leslie Lamport whether there is an algorithm with a constant number of communication bits per process that satisfies every reasonable fairness and failure-tolerance requirement that Lamport conceived of (Lamport's solution used n factorial communication variables vs.
Parrot virtual machineParrot was a register-based process virtual machine designed to run dynamic languages efficiently. It is possible to compile Parrot assembly language and Parrot intermediate representation (PIR, an intermediate language) to Parrot bytecode and execute it. Parrot is free and open-source software. Parrot was started by the Perl community and is developed with help from the open-source and free software communities. As a result, it is focused on license compatibility with Perl (Artistic License 2.
Volatile (computer programming)In computer programming, volatile means that a value is prone to change over time, outside the control of some code. Volatility has implications within function calling conventions, and also impacts how variables are stored, accessed and cached. In the C, C++, C#, and Java programming languages, the volatile keyword indicates that a value may change between different accesses, even if it does not appear to be modified. This keyword prevents an optimizing compiler from optimizing away subsequent reads or writes and thus incorrectly reusing a stale value or omitting writes.
Nullable typeNullable types are a feature of some programming languages which allow a value to be set to the special value NULL instead of the usual possible values of the data type. In statically typed languages, a nullable type is an option type, while in dynamically typed languages (where values have types, but variables do not), equivalent behavior is provided by having a single null value. NULL is frequently used to represent a missing value or invalid value, such as from a function that failed to return or a missing field in a database, as in NULL in SQL.
Peterson's algorithmPeterson's algorithm (or Peterson's solution) is a concurrent programming algorithm for mutual exclusion that allows two or more processes to share a single-use resource without conflict, using only shared memory for communication. It was formulated by Gary L. Peterson in 1981. While Peterson's original formulation worked with only two processes, the algorithm can be generalized for more than two. The algorithm uses two variables: flag and turn. A flag[n] value of true indicates that the process n wants to enter the critical section.
