How Are Variables Initialized in C , and When Does Automatic Initialization Occur?

Variable Initialization in C : Unraveling Automatic and Controlled Initialization

In contrast to popular belief, int variables in C are not automatically initialized to 0. This misconception leads to unexpected behavior and possible runtime errors, as observed in the code provided:

int main() {
    int a[10];
    int i;
    cout << i << endl;
    for (int i = 0; i < 10; i++)
        cout << a[i] << " ";
    return 0;
}

Understanding the rules governing variable initialization is crucial in C . Automatic initialization only occurs under specific conditions:

• Class/Struct Instances:
  Classes and structs are constructed using the default constructor, which automatically initializes primitive types within the object.
• Array Initializer Syntax:
  Arrays can be initialized using the '{}' syntax. Values within the braces override the default initialization, while unspecified values are set to zero.
• Non-Aggregate Classes/Structs:
  Similar to array initialization, non-aggregate classes/structs can be initialized using '{}' to invoke the default constructor.
• Global/Extern Variables:
  Global and extern variables are automatically initialized to zero.
• Static Variables:
  Variables declared as static (in function scope or globally) are initialized with zeros.

It's imperative to explicitly initialize any variable of a plain type. Relying on automatic initialization can lead to unpredictable outcomes and hinder code robustness.

The above is the detailed content of How Are Variables Initialized in C , and When Does Automatic Initialization Occur?. For more information, please follow other related articles on the PHP Chinese website!