What does 'dynamic memory allocation' allow in programming?

Dynamic memory allocation refers to the process of allocating memory during the execution of a program, rather than at compile time. This capability allows a program to request and release memory as needed while it is running, which is particularly useful for handling varying amounts of data or unexpected inputs.

When using dynamic memory allocation, developers can create data structures whose size may not be known until the program is running, such as arrays, linked lists, or other complex data types. This flexibility is essential in situations where the amount of data can grow or shrink, ensuring that a program can efficiently utilize available memory resources without leading to waste or overflow.

In contrast, static memory allocation happens at compile time, making option one incorrect. While freeing up memory when it's no longer in use is an important aspect of memory management, it is a secondary process related to dynamic allocation but does not describe the primary purpose of dynamic memory allocation itself. Managing stack memory pertains to a different part of memory management, typically for local variables and function calls, and does not relate to the concept of dynamic allocation directly. Thus, the ability to allocate memory during runtime is the key characteristic that defines dynamic memory allocation.