Editing Struct (C programming language) (section)

== Initialization ==

There are three ways to initialize a structure. 

For the type:

<syntaxhighlight lang="c">
struct point_t {
   int x;
   int y;
};
</syntaxhighlight>

''C89-style initializers'' are used when contiguous members may be given.<ref>{{cite book | first1 = Al | last1 = Kelley | first2 = Ira | last2 = Pohl | year = 2004 | url = https://archive.org/details/bookoncprogrammi00kell/page/418 | edition = Fourth | title = A Book On C: Programming in C | isbn = 0-201-18399-4 | pages = [https://archive.org/details/bookoncprogrammi00kell/page/418 418] | url-access = registration }}</ref> For example:

<syntaxhighlight lang="c">
struct point_t a = { 1, 2 };
</syntaxhighlight>

For non contiguous or out of order members list, ''designated initializer'' style may be used.<ref>{{cite web | url=https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.3.0/com.ibm.zos.v2r3.cbclx01/strin.htm | title=IBM Linux compilers. Initialization of structures and unions}}</ref> For example:

<syntaxhighlight lang="c">
struct point_t a = { .y = 2, .x = 1 };
</syntaxhighlight>

If an initializer is given or if the object is [[Static memory allocation|statically allocated]], omitted elements are initialized to 0.

A third way of initializing a structure is to copy the value of an existing object of the same type. For example:

<syntaxhighlight lang="c">
struct point_t b = a;
</syntaxhighlight>