B) Shortest Job First
(SJF) : In this method, when the CPU is
available it is assigned to that job with the smallest next CPU
burst. FCFS is used. The following example illustrates. The
following is the order in which the jobs arrive and their burst times.
The difficulty
with SJF is knowing the length of the next, CPU burst
by predicting. It is done as follows.
Let Tn be the length of the nth CPU burst time.
tn be the predicted value of the nth CPU burst
time.
Tn+1 = tn + ( 1
- µ ) Tn
The formula defines
an exponential average.
t
- Current Burst Time.
T - Previous Burst Time.
µ - Relative Weightage between the
Fast and Recent burst times.