Subroutine in the context of Naming convention (programming)

In compiler optimization, register allocation is the process of assigning local automatic variables and expression results to a limited number of processor registers.

Register allocation can happen over a basic block (local register allocation), over a whole function/procedure (global register allocation), or across function boundaries traversed via call-graph (interprocedural register allocation). When done per function/procedure the calling convention may require insertion of save/restore around each call-site.

An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build such a connection or interface is called an API specification. A computer system that meets this standard is said to implement or expose an API. The term API may refer either to the specification or to the implementation.

In contrast to a user interface, which connects a computer to a person, an application programming interface connects computers or pieces of software to each other. It is not intended to be used directly by a person (the end user) other than a computer programmer who is incorporating it into software. An API is often made up of different parts which act as tools or services that are available to the programmer. A program or a programmer that uses one of these parts is said to call that portion of the API. The calls that make up the API are also known as subroutines, methods, requests, or endpoints. An API specification defines these calls, meaning that it explains how to use or implement them.

In computing, multi-touch is technology that enables a surface (a touchpad or touchscreen) to recognize the presence of more than one point of contact with the surface at the same time. The origins of multitouch began at CERN, MIT, University of Toronto, Carnegie Mellon University and Bell Labs in the 1970s. CERN started using multi-touch screens as early as 1976 for the controls of the Super Proton Synchrotron. Capacitive multi-touch displays were popularized by Apple's iPhone in 2007. Multi-touch may be used to implement additional functionality, such as pinch to zoom or to activate certain subroutines attached to predefined gestures using gesture recognition.

Several uses of the term multi-touch resulted from the quick developments in this field, and many companies using the term to market older technology which is called gesture-enhanced single-touch or several other terms by other companies and researchers. Several other similar or related terms attempt to differentiate between whether a device can exactly determine or only approximate the location of different points of contact to further differentiate between the various technological capabilities, but they are often used as synonyms in marketing.

In vector computer graphics, CAD systems, and geographic information systems, a geometric primitive (or prim) is the simplest (i.e. 'atomic' or irreducible) geometric shape that the system can handle (draw, store). Sometimes the subroutines that draw the corresponding objects are called "geometric primitives" as well. The most "primitive" primitives are point and straight line segments, which were all that early vector graphics systems had.

In constructive solid geometry, primitives are simple geometric shapes such as a cube, cylinder, sphere, cone, pyramid, torus.Modern 2D computer graphics systems may operate with primitives which are curves (segments of straight lines, circles and more complicated curves), as well as shapes (boxes, arbitrary polygons, circles).

Code reuse is the practice of using existing source code to develop software instead of writing new code. Software reuse is a broader term that implies using any existing software asset to develop software instead of developing it again. An asset that is relatively easy to reuse and offers significant value is considered to have high reusability.

Code reuse may be achieved different ways depending on a complexity of a programming language chosen and range from a lower-level approaches like code copy-pasting (e.g. via snippets), simple functions (procedures or subroutines) or a bunch of objects or functions organized into modules (e.g. libraries) or custom namespaces, and packages, frameworks or software suites in higher-levels.

In the context of an operating system, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer. A driver provides a software interface to hardware devices, enabling operating systems and other computer programs to access hardware functions without needing to know precise details about the hardware.

A driver communicates with the device through the computer bus or communications subsystem to which the hardware connects. When a calling program invokes a routine in the driver, the driver issues commands to the device (drives it). Once the device sends data back to the driver, the driver may invoke routines in the original calling program.

In computer programming, a runtime system or runtime environment is a sub-system that exists in the computer where a program is created, as well as in the computers where the program is intended to be run. The name comes from the compile time and runtime division from compiled languages, which similarly distinguishes the computer processes involved in the creation of a program (compilation) and its execution in the target machine (the runtime).

Most programming languages have some form of runtime system that provides an environment in which programs run. This environment may address a number of issues including the management of application memory, how the program accesses variables, mechanisms for passing parameters between procedures, interfacing with the operating system (OS), among others. The compiler makes assumptions depending on the specific runtime system to generate correct code. Typically the runtime system will have some responsibility for setting up and managing the stack and heap, and may include features such as garbage collection, threads or other dynamic features built into the language.

In computer programming, housekeeping can refer to either a standard entry or exit routine appended to a user-written block of code (such as a subroutine or function, sometimes as a function prologue and epilogue) at its entry and exit or to any other automated or manual software process whereby a computer is cleaned up after usage (e.g. freeing resources such as virtual memory). This might include such activities as removing or archiving logs that the system has made as a result of the users activities, or deletion of temporary files which may otherwise simply take up space. Housekeeping can be described as a necessary chore, required to perform a particular computer's normal activity but not necessarily part of the algorithm. For cleaning up computer disk storage, utility software usually exists for this purpose such as data compression software - to "shrink" files and release disk space and defragmentation programs - to improve disk performance.

Instructions per second (IPS) is a measure of a computer's processor speed. For complex instruction set computers (CISCs), different instructions take different amounts of time, so the value measured depends on the instruction mix; even for comparing processors in the same family the IPS measurement can be problematic. Many reported IPS values have represented "peak" execution rates on artificial instruction sequences with few branches and no cache contention, whereas realistic workloads typically lead to significantly lower IPS values. Memory hierarchy also greatly affects processor performance, an issue barely considered in IPS calculations. Because of these problems, synthetic benchmarks such as Dhrystone are now generally used to estimate computer performance in commonly used applications, and raw IPS has fallen into disuse.

The term is commonly used in association with a metric prefix (k, M, G, T, P, or E) to form kilo instructions per second (kIPS), mega instructions per second (MIPS), giga instructions per second (GIPS) and so on. Formerly TIPS was used occasionally for "thousand IPS".

In computer science, a calling convention is an implementation-level (low-level) scheme for how subroutines or functions receive parameters from their caller and how they return a result. When some code calls a function, design choices have been taken for where and how parameters are passed to that function, and where and how results are returned from that function, with these transfers typically done via certain registers or within a stack frame on the call stack. There are design choices for how the tasks of preparing for a function call and restoring the environment after the function has completed are divided between the caller and the callee. Some calling convention specifies the way every function should get called. The correct calling convention should be used for every function call, to allow the correct and reliable execution of the whole program using these functions.

In mathematics and computer science, a higher-order function (HOF) is a function that does at least one of the following:

• takes one or more functions as arguments (i.e. a procedural parameter, which is a parameter of a procedure that is itself a procedure),
• returns a function as its result.

All other functions are first-order functions. In mathematics higher-order functions are also termed operators or functionals. The differential operator in calculus is a common example, since it maps a function to its derivative, also a function. Higher-order functions should not be confused with other uses of the word "functor" throughout mathematics, see Functor (disambiguation).

In computing, memoization or memoisation is an optimization technique used primarily to speed up computer programs. It works by storing the results of expensive calls to pure functions, so that these results can be returned quickly should the same inputs occur again. It is a type of caching, normally implemented using a hash table, and a typical example of a space–time tradeoff, where the runtime of a program is reduced by increasing its memory usage. Memoization can be implemented in any programming language, though some languages have built-in support that make it easy for the programmer to memoize a function, and others memoize certain functions by default.

Memoization has also been used in other contexts (and for purposes other than speed gains), such as in simple mutually recursive descent parsing. In the context of some logic programming languages, memoization is also known as tabling.

In computer science, function composition is an act or mechanism to combine simple functions to build more ones. Like the usual composition of functions in mathematics, the result of each function is passed as the argument of the next, and the result of the last one is the result of the whole.

Programmers frequently apply functions to results of other functions, and almost all programming languages allow it. In some cases, the composition of functions is interesting as a function in its own right, to be used later. Such a function can always be defined but languages with first-class functions make it easier.

In computer programming languages, an identifier is a lexical token (also called a symbol, but not to be confused with the symbol primitive data type) that names the language's entities. Some of the kinds of entities an identifier might denote include variables, data types, labels, subroutines, and modules.

In computer programming, a return statement causes execution to leave the current subroutine and resume at the point in the code immediately after the instruction which called the subroutine, known as its return address. The return address is saved by the calling routine, today usually on the process's call stack or in a register. Return statements in many programming languages allow a function to specify a return value to be passed back to the code that called the function.

In computer science, a tail call is a subroutine call performed as the final action of a procedure.If the target of a tail is the same subroutine, the subroutine is said to be tail recursive, which is a special case of direct recursion. Tail recursion (or tail-end recursion) is particularly useful, and is often easy to optimize in implementations.

Tail calls can be implemented without adding a new stack frame to the call stack. Most of the frame of the current procedure is no longer needed, and can be replaced by the frame of the tail call, modified as appropriate (similar to overlay for processes, but for function calls). The program can then jump to the called subroutine. Producing such code instead of a standard call sequence is called tail-call elimination or tail-call optimization. Tail-call elimination allows procedure calls in tail position to be implemented as efficiently as goto statements, thus allowing efficient structured programming. In the words of Guy L. Steele, "in general, procedure calls may be usefully thought of as GOTO statements which also pass parameters, and can be uniformly coded as [machine code] JUMP instructions."