Describe the working of the buddy system for memory allocation.

The buddy system is a memory allocation technique used in operating systems to manage memory efficiently. It involves dividing the available memory into fixed-size blocks, which are then allocated to processes as needed.

Here is a step-by-step description of how the buddy system works:

1. Initially, the entire available memory is considered as a single block of the largest size.
2. When a process requests memory, the system checks if there is a block of the required size available. If there is, it is allocated to the process.
3. If there is no block of the required size available, the system looks for the next larger block that is free and splits it into two equal-sized smaller blocks, known as buddies.
4. The buddy system maintains a binary tree structure to keep track of the free and allocated blocks. Each node in the tree represents a block, and the left and right child nodes represent the two buddies.
5. The splitting process continues recursively until a block of the required size is obtained.
6. Once a block is allocated to a process, it is marked as allocated in the binary tree.
7. When a process releases memory, the system checks if its buddy is also free. If the buddy is free, the two buddies are merged back into a larger block.
8. The merging process continues recursively until no more merging is possible.
9. The merged block is then marked as free in the binary tree.

The buddy system ensures that memory is allocated and deallocated in power-of-two block sizes, which simplifies the allocation process and reduces fragmentation. It also allows for efficient coalescing of free blocks, minimizing wasted memory.

Overall, the buddy system provides a balanced approach to memory allocation, balancing the need for efficient allocation and deallocation with the goal of minimizing fragmentation.