Advanced Placement (AP) Computer Science

What is a 'default value' in programming?

1. The value assigned after user input

2. The initial setting of a variable when the program starts

3. A value assigned during compilation

4. The final output of a program

The correct answer is: The initial setting of a variable when the program starts

A default value in programming refers to the initial setting of a variable when the program starts. This means that before any user input or operation is performed, the variable is given a predefined value that serves as a placeholder. This is important for ensuring that variables do not contain undefined values, which can lead to errors during execution. In many programming languages, if a variable is not explicitly initialized by the programmer, it may automatically receive a default value specific to its type. For instance, in languages like Java, an int variable will default to 0, while a boolean will default to false. This helps prevent issues with uninitialized variables and allows the program to run more smoothly from the outset. Understanding default values is crucial because they establish a baseline for how variables behave and interact with other parts of the program. Without these initial values, the program could encounter unpredictable results if it relies on variables that haven’t been properly set.