Memory allocation in C refers to the process of reserving a specific amount of memory space for a variable or data structure in a C program. There are two main types of memory allocation in C: static and dynamic.

Static memory allocation refers to the allocation of memory space at compile time. This means that the memory space is reserved when the program is compiled, and the size of the memory space cannot be changed during runtime. An example of static memory allocation is the declaration of a global variable or a static local variable within a function.

Dynamic memory allocation refers to the allocation of memory space at runtime. This means that the memory space is reserved when the program is executed, and the size of the memory space can be changed during runtime. An example of dynamic memory allocation is the use of the malloc() or calloc() functions to allocate memory space for a variable or data structure.

In C, dynamic memory allocation is typically used when the size of a variable or data structure is unknown at compile time or when the program needs to allocate memory space based on user input. Static memory allocation is typically used when the size of a variable or data structure is known at compile time and does not need to be changed during runtime.