Question

Apply the first-fit, best-fit, and worst-fit algorithms separately the given processes in sequence from P1 to P4 and Identify which algorithm makes the most efficient use of memory? Show every step for process assignment, also discuss the internal and external fragmentation in the scenario.

220 KB P1 250 KB P2 390 KB 460 KB P4 P3 150 KB 100 KB 517 KB 340 KB Processes 730 KB Memory Partition

Answer 1

P1 - 250 KB, P2 - 390 KB, P3 - 150 KB, P4 - 517 KB

First fit algorithm : The first job claims the first memory which is large enough for the process

Memory block size	Job number	Job size	Status	Internal fragmentation
220 KB	P3	150 KB	Busy	70 KB
460 KB	P1	250 KB	Busy	210 KB
100 KB			Free	100 KB
340 KB			Free	340 KB
730 KB	P2	390 KB	Busy	340 KB
Total available : 1850 KB		Total used : 790 KB		Total I. F : 1060 KB

Best fit : It allocates the smallest memory which is large enough to hold the process

Memory block size	Job number	Job size	Status	Internal fragmentation
220 KB	P3	150 KB	Busy	70 KB
460 KB	P2	390 KB	Busy	70 KB
100 KB			Free	100 KB
340 KB	P1	250 KB	Busy	90 KB
730 KB	P4	517 KB	Busy	213 KB
Total available : 1850 KB		Total used : 1307 KB		Total I. F : 543 KB

Worst fit : The algorithm allocates the largest memory which is enough to hold the process.

Memory block size	Job number	Job size	Status	Internal fragmentation
220 KB			Free	220 Kb
460 KB	P2	390 KB	Busy	70 KB
100 KB			Free	100 KB
340 KB	P3	150 KB	Busy	190 KB
730 KB	P1	250 KB	Busy	480 KB
Total available : 1850 KB		Total used : 790 KB		Total I. F : 1060 KB

Best fit algorithm makes the most efficient use of memory. In these algorithms, internal fragmentation happens.