What are the functions of the reserve function in the C language?

In the C language, the reserve function is commonly used for pre-allocating memory space in container classes such as vectors and strings. Its functionality includes:

1. Preallocate memory space: The reserve function can allocate a certain amount of memory space in the container to reduce the cost of dynamically increasing memory space.
2. Enhance performance: By pre-allocating enough memory space, it can reduce frequent memory allocation and release operations, thus improving the program’s performance.
3. Avoid dynamic resizing: By preallocating enough memory space using the reserve function, you can prevent frequent dynamic resizing operations when inserting elements, thus improving the efficiency of the program.

It is important to note that the reserve function only pre-allocates memory space and does not change the size of the container. The pre-allocated space can be actually used by inserting elements.