Initialization (programming): Difference between revisions

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{{Short description|Assignment of an initial value for variable}}

In [[computer programming]], '''initialization''' (or '''initialisation)''' is the [[Assignment (computer science)|assignment]] of an initial value for a [[data object]] or variable. The manner in which initialization is performed depends on the [[programming language]], as well as the type, storage class, etc., of an object to be initialized. Programming constructs which perform initialization are typically called '''initializers''' and '''initializer lists'''. Initialization is distinct from (and preceded by) [[declaration (computer programming)|declaration]], although the two can sometimes be conflated in practice. The complement of initialization is [[finalization]], which is primarily used for objects, but not variables.

Initialization is done either by statically embedding the value at compile time, or else by assignment at [[Run time (program lifecycle phase)|run time]]. A section of code that performs such initialization is generally known as "initialization code" and may include other, one-time-only, functions such as opening files; in [[object-oriented programming]], initialization code may be part of a ''[[Constructor (object-oriented programming)|constructor]]'' (class method) or an ''initializer'' (instance method). Setting a memory ___location to [[hexadecimal]] zeroes is also sometimes known as "clearing" and is often performed by an [[exclusive or]] instruction (both operands specifying the same variable), at [[machine code]] level, since it requires no additional memory access.

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Sometimes the term "initializer list" is also used to refer to the list of expressions in the array or struct initializer.

[[C++11]] provides for a [[C++11#Initializer_lists|more powerful concept of initializer lists]], by means of a template, called <tt>{{mono|std::initializer_list</tt>}}.

===Default initialization===