what is a buddy systemwe are dividing the memory

Question

What is a buddy system?

We are dividing the memory as powers of two therefore the division will be 2, 4, 8, 16, 32, 64, 128, 256...i.e. in powers of 2 as well as we are selecting the space which is smallest but large enough to hold a process. Assume we have 1M memory. If a process 70k enters we are able to choose the 128k which will be the best fit for the process. Thus divide the 1M into 512k each. After that a further division of 256k each in one 512k afterward one of the 256 is divided into further 128keach and place the process in that. Similarly to that if another process enters the division and placing will continue.

Process A enters of 0k

 

A

          128     128         256                                 512

Process B enters of 35k

A

B

 

.

 

128    64  64     256                           512                                                                         

Process c enters of 80k

A

B

C

           128     64   64  128    128                          512

Process A terminates

128

B

C

         64   64  128    128                         512

Process D enters of 60k

128

B

D

C

                      64  64    128   128          512

Process B terminates

128

64

D

C

                              64   128   128                          512

Process D terminates

128

64

64

C

                                         128   128                     512

Process C terminates

128

64

64

128

128

512

 

Subsequent to this all the free spaces will join together. Later than the two adjacent processes having same space completed they will combine together and at last when all the processes are over the 1M memory will get back.