Initialization

Initialization of a variable provides an initial value at the time of construction.

The initial value may be provided in the initializer section of a declaration. Initialization also takes place during function calls: function parameters and the function return values are also initialized.

For each declarator, the initializer may be one of the following:

assignment-expression	(1)
{ initializer-list }	(2)
{ initializer-list , }	(3)

1) return value of an assignment expression

2) brace-enclosed initializer-list cannot be empty

3) trailing comma may follow an initializer-list

If no initializer is provided, the rules of default initialization apply.

• Default initialization
• Arithmetic-type initialization
• Pointer-type initialization
• Array-type initialization
• Struct-type initialization
• Union-type initialization

Example

Three simple initializers based on the definition above.

Run this code

int main(void)
{
    int a1;
    int a2 = a1=8;   /* assignment-expression  */
 
    int a3 = {0};    /* { initializer-list }   */
    int a4 = {0,};   /* { initializer-list , } */
 
    return 0;
}

Possible output:

(none)

See also

C++ documentation for initialization