# operating system

**Topics:**Scheduling, Process states, Programming language

**Pages:**3 (464 words)

**Published:**September 29, 2013

For implementing SJF algorithm with preemption, we consider the arrival times of each process, the burst times of all the previously arrived processes. After the arrival of all the processes into the ready queue, the average waiting time and turn around time can be calculated by using the above algorithm.

ALGORITHM:

1) start

2) read the no of processes to n

3) initialize i to 0

4) if ia[j] then

a) swap a[i] and a[j]

b) swap at[i] and at[j]

c) swap b[i] and b[j]

8) from i=0 to n do

a) w[i]=s-b[i]-at[i]

b) s=s+a[i]

c) avg=avg+w[i]

9)tt=tt+avg

10) tt=tt/n

11) avg=avg/n

12)write the turn around time and average waiting time

13) stop

2) AIM: To write a program on Shortest Job First algorithm with Non-Preemption Description:

Initially, In the shortest job first algorithm with non-preemption, the sorting of the process can be done based on their burst time in ascending order. The above algorithm calculates the averaging waiting time and turn around time of each process . ALGORITHM:

1) start

2) read the number of process into n

3) for i=0 to n step1 do

a) read the burst time of process into b[i]

b) check if b[i] is less than 0

i. write invalid input

ii. goto step 11

c) tt = tt+b[i]

4) for i=0 to n do step1

i. for j=1 to n step1 do

if b[i]>b[j]

t=b[j]

b[i]=b[j]

b[j]=t

5) assign 0 to w[0]

6) for i=1 to n do

w[i]=w[i-1]+b[i]

avg=avg+w[i]

7) tt=tt+avg

8) avg=avg/n

9) tt=tt/n

10) Print the average waiting time and turn around time

11) Stop

3) Aim: To write a c program to simulate First Come First Served(FCFS)algorithm using CPU Scheduling.

Description:

In FCFS algorithm, which ever the process that enters first in the ready queue will be allocated CPU first. Initially, the waiting time of the first process is kept zero. In this algorithm, the waiting time of the second process is the burst time of the first process and the...

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