What is the primary characteristic of a local variable?

The primary characteristic of a local variable is that it is declared within and used only in a specific sub-program. Local variables are designed to have limited scope, meaning they can only be accessed and manipulated within the block or function where they are created. This helps prevent naming conflicts and enhances modularity in programming, as each sub-program can use local variables without affecting the values used elsewhere in the program.

In contrast, global variables can be accessed throughout the entire program, which can lead to unintended side effects if multiple parts of the code attempt to modify them. The idea behind local variables ensuring encapsulation and better management of data within a specific function or method makes them essential for writing clean and maintainable code.

Finally, local variables do occupy memory while the sub-program is in use; they may not hold constant values as they can be changed during execution, which distinguishes them from constants. Thus, defining a variable as local inherently includes the constraints of its scope and lifetime.