How is memory reservation for slices in programming languages implemented?

In Go language, a slice is a structure that contains a pointer to an array, a length, and a capacity. When creating a slice, memory for the elements is reserved in the array it points to.

When a slice is created using the make function, for example make([]int, length, capacity), an array with the specified capacity is allocated. If the capacity is exceeded when adding elements, Go automatically allocates a new larger array, copies the data, and updates the slice pointer.

Example:

s := make([]int, 0, 5) // slice with length 0 and capacity 5
s = append(s, 1, 2, 3) // adding elements

Thus, memory reservation occurs in advance for the specified capacity, which increases efficiency when adding elements.