Dereference operator

Ada Lovelace, whose notes added to the end of Luigi Menabrea's paper included the first algorithm designed for processing by an Analytical Engine. She is often recognized as history's first computer programmer.

Unary operator (i.e. one with a single operand) found in C-like languages that include pointer variables.

- Dereference operator

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Variable (computer science)

Abstract storage location paired with an associated symbolic name, which contains some known or unknown quantity of information referred to as a value; or in simpler terms, a variable is a container for a particular set of bits or type of data .

Ada Lovelace, whose notes added to the end of Luigi Menabrea's paper included the first algorithm designed for processing by an Analytical Engine. She is often recognized as history's first computer programmer.

In imperative programming languages, values can generally be accessed or changed at any time.

Asterisk

Typographical symbol.

The asteriskos used in an early Greek papyrus.
Early asterisks seen in the margin of Greek papyrus.
The Star of Life may represent emergency medical services
Asterisks used to illustrate a section break in Alice's Adventures in Wonderland

In some programming languages such as the C, C++, and Go programming languages, the asterisk is used to dereference or declare a pointer variable.

Syntactic sugar

Syntax within a programming language that is designed to make things easier to read or to express.

Charles Babbage, sometimes referred to as the "father of computing".

In the C language, the notation is syntactic sugar for . Likewise, the notation is syntactic sugar for accessing members using the dereference operator.

Pointer (computer programming)

Object in many programming languages that stores a memory address.

Pointer a pointing to the memory address associated with variable b. In this diagram, the computing architecture uses the same address space and data primitive for both pointers and non-pointers; this need should not be the case.

A pointer references a location in memory, and obtaining the value stored at that location is known as dereferencing the pointer.

C syntax

Set of rules governing writing of software in the C language.

In order to accomplish that task, the unary dereference operator, denoted by an asterisk (*), is used.

Sigil (computer programming)

Symbol affixed to a variable name, showing the variable's datatype or scope, usually a prefix, as in , where is the sigil.

Ada Lovelace, whose notes added to the end of Luigi Menabrea's paper included the first algorithm designed for processing by an Analytical Engine. She is often recognized as history's first computer programmer.

While this may seem similar to a sigil, it is properly a unary operator for lexical indirection, similar to the dereference operator for pointers in C, as noticeable from the fact that the dollar sign is omitted when assigning to a variable.

Dead reckoning

Process of calculating current position of some moving object by using a previously determined position, or fix, and then incorporating estimates of speed, heading direction, and course over elapsed time.

The navigator plots their 9 a.m. position, indicated by the triangle, and, using their course and speed, estimates their own position at 9:30 and 10 a.m.
Drift is the angle between the heading of the airplane and the desired track. A is the last known position (fix, usually shown with a circle). B is the wind direction (usually shown with a plus sign). C is true position (usually shown with a triangle).
Dead reckoning navigation tools in coastal navigation
British P10 Magnetic Compass with dead reckoning navigation tools

This property is particularly important for performance when used in conjunction with arrays of structures because data can be directly accessed, without going through a pointer dereference.

Reference (computer science)

Value that enables a program to indirectly access a particular data, such as a variable's value or a record, in the computer's memory or in some other storage device.

Ada Lovelace, whose notes added to the end of Luigi Menabrea's paper included the first algorithm designed for processing by an Analytical Engine. She is often recognized as history's first computer programmer.

The reference is said to refer to the datum, and accessing the datum is called dereferencing the reference.

At sign

Normally read aloud as "at"; it is also commonly called the at symbol, commercial at, or address sign.

@ symbol used as the initial "a" for the "amin" (amen) formula in the Bulgarian of the Manasses Chronicle (c. 1345).
The Aragonese @ symbol used in the 1448 "taula de Ariza" registry to denote a wheat shipment from Castile to the Kingdom of Aragon.
@ used to signify French "à" ("at") from a 1674 protocol from a Swedish court (Arboga rådhusrätt och magistrat)
Protester with banner showing "La revolución está en nosotr@s"
Bicameral @ letter as used in the Koalib language.
X-SAMPA uses an @ as a substitute for ə, which it resembles in some fonts.
@ on a DVK Soviet computer (c. 1984)

In assembly language, @ is sometimes used as a dereference operator.

Value (computer science)

Representation of some entity that can be manipulated by a program.

Charles Babbage, sometimes referred to as the "father of computing".

In many languages, notably the C family, l-values have storage addresses that are programmatically accessible to the running program (e.g., via some address-of operator like "&" in C/C++), meaning that they are variables or de-referenced references to a certain memory location.