Final answer:
Memory allocations for the buddy system with sizes 2, 1, 2, 4 are made in the smallest available blocks that fit. The header array is updated with each allocation. Upon releasing blocks, the system updates the header array and combines adjacent free blocks if they are buddies.
Step-by-step explanation:
Memory Layout for Buddy System Requests
The buddy system is a memory allocation and management algorithm that divvies up memory into partitions to try and minimize the memory wasted. With 5 different hole sizes ranging from 2⁰ through 2⁴, each request will occupy the smallest hole that is large enough to accommodate it.
To accommodate the sequence of requests of sizes 2, 1, 2, 4, we would proceed as follows:
The first request for size 2 might occupy a block of size 2² (since that's the smallest that fits).
The request for size 1 would use a block of 2⁰, if available, otherwise it may split a block of 2¹.
The following request for size 2 might take another block of 2² if another one is available.
Last, the request for size 4 is accommodated by a block of size 2² to fit it exactly or by splitting a larger block if necessary.
For the header array H, it would be updated to reflect the newly allocated blocks with the corresponding block sizes showing as being used.
Releasing Blocks in Buddy System
When blocks of size 1 at addresses 4, 10, 5, 11 are released:
After releasing block at address 4, the header array H is updated to show this block as free.
Releasing the block at address 10 may lead to coalescing with adjacent free blocks if any exist.
Similarly, releasing block at address 5 is followed by an update to H, and possible coalescing.
Releasing the last block at address 11 would also update the H array and may result in coalescing with the block released previously if they are buddies.
After each release, the H array is checked for possible 'buddies' - free blocks of the same size that are adjacent. If there are any, they are combined to form a larger free block.