When exactly does memory allocation occur in the dynamic memory area during program execution?

Memory allocation in the dynamic area (heap) occurs during program execution at the moment of calling functions that explicitly request memory, such as malloc in C, new in C++, or using corresponding methods in Swift (UnsafeMutablePointer.allocate) or Objective-C (alloc). This does not happen during compilation, but precisely at runtime when the program needs to create objects or data structures of variable size or with a lifetime exceeding the current function. Thus, memory is allocated "on the fly" upon request, and its size and lifetime are determined dynamically.