OPERATING SYSTEMS LAB MANUAL
INDEX
1. Simulate the following CPU scheduling algorithmsi. Round
Robinii. SJFiii. FCFSiv. Priority2. Loading executable programs
into memory and execute system call implementation read(),write(),
open() and close()3. Multiprogramming-Memory management
implementation of fork(),wait(),exec() & exit() system calls4.
Simulate all file allocation strategiesi. Sequentialii. Indexed
iii. Linked5. Simulate MVT and MFT6. Simulate all File Organization
Techniquesi. Single level directoryii. Two level iii. Hierarchical
iv. DAG7. Simulate Bankers algorithm for deadlock avoidance8.
Simulate Bankers Algorithm for Deadlock prevention9. Simulate all
page replacement algorithmsi. FIFO ii. LRUiii. LFU Etc. 10.
Simulate Paging Technique of memory management.
1) Simulate the following CPU scheduling algorithms
a) FCFSb) SJFc) Priorityd) Round Robin
Description:FCFS (first-come-first-serve) Scheduling First-come,
First served is simplest scheduling algorithm Ready queue is a FIFO
queue: Longest waiting process at the front of queue New ready
processes join the rear Non-preemptive: executes until voluntarily
gives up CPU finished or waits for some event Problem: CPU bound
process may require a long CPU burst Other processes, with very
short CPU bursts, wait in queue reduces CPU and I/O device
utilization
SJF (shortest-job-first) Scheduling Assume the next burst time
of each process is known SJF selects process which has the shortest
burst time Optimal algorithm because it has the shortest average
waiting time Impossible to know in advance OS knows the past burst
times- make a prediction using an average Non-preemptive Or
preemptive Shortest remaining time first Interrupts running process
if a new process enters the queue New process must have shorter
burst than remaining time
Round Robin Scheduling Similar to FCFS, but preemption to switch
between processes Time quantum(time slice) is a small unit of time
(10 to 100 ms) Process is executed on the CPU for at most one time
quantum Implemented by using the ready queue as a circular queue
Head process gets the CPU Uses less than a time quantum implies
gives up the CPU voluntary Uses full time quantum implies timer
will cause an interrupt
Context switch will be executed Process will be put at the tail
of queue
Priority Scheduling Assume a priority is associated with each
process Assume all processes arrive at the same time Select highest
priority process from the ready queue Let T be the next CPU burst
of a process SJF is a special case of priority scheduling
Equal-priority processes are scheduled in FCFS order PRIORITY can
be preemptive or Non-preemptive Priorities can be defined
internally Memory requirements, number of open files, burst
times
a) FCFS:
AIM: A program to simulate the FCFS CPU scheduling algorithm
PROGRAM:
#include#includestruct process{ int at,ts,st,ft,ta; float
nta;};main(){ struct process p[20]; int n,i,j; float
tamean=0,ntamean=0; clrscr(); printf("\nEnter Number of Processes::
"); scanf("%d",&n);
for(i=0;i---------------------------------------------Do U want to
continue ::(Y:n) n */
II. Index file Allocation Method
PROGRAM :
#include#include#includeint n;void main(){ int
b[20],b1[20],i,j,blocks[20][20],sz[20]; char F[20][20],S[20],ch;
clrscr(); printf("\n Enter no. of Files ::"); scanf("%d",&n);
for(i=0;i---------------------------------------------Do U want to
continue ::(Y:n)0
III. Linked file Allocation Method
PROGRAM
#include#include#includeint n;void main(){ int
b[20],b1[20],i,j,blocks[20][20],sz[20]; char F[20][20],S[20],ch;
int sb[20],eb[20],x; clrscr(); printf("\n Enter no. of Files ::");
scanf("%d",&n);
for(i=0;i104->600->---------------------------------------------
Do U want to continue ::(Y:n)1
Enter the Filename ::sudee
Fname Fsize Bsize Nblocks
Blocks---------------------------------------------sudee 1 1024 1
200->201->500->---------------------------------------------Do
U want to continue ::(Y:n)0
5. Simulate the MVT and MFT.Description:Memory management1. CPU
runs program instructions only when program is in memory. 1.
Programs do I/O sometimes IMPLY CPU wasted.1. Solution :
Multiprogramming1. Multiple programs share the memory1. One program
at a time gets CPU1. Simultaneous resource possession1. Better
performance
Multiple Programming with Fixed Number of Tasks (MFT):IBM in
their Mainframe Operating system OS/MFT implements the MFT concept.
OS/MFT uses fixed partitioning concept to load programs into main
memory.Fixed Partitioning:1. In fixed partitioning concept, RAM is
divided into set of fixed partitions of equal size.1. Programs
having the size less than the partition size are loaded into
memory1. Programs having size more than the size of partition size
is rejected1. The program having the size less than the partition
size will lead to internal fragmentation1. If all partitions are
allocated and if a new program is to be loaded, the program that
leads to maximum internal fragmentation can be replaced.
Multi-programming with variable number of tasks (MVT):IBM in
their Mainframe Operating system OS/MVT implements the MVT concept.
OS/MVT uses dynamic partitioning concept to load programs into main
memory.
Dynamic Partitioning: Initially RAM is portioned according to
the size of programs to be loaded into Memory till such time that
no other program can be loaded. The left over memory is called a
hole which is too small to fit any process When a new program is to
be loaded into memory look for the partition, which leads to least
external fragmentation and load the program. The space that is not
used in a partition is called as external fragmentation
Multi-programming with variable number of tasks (MVT):
#include#includemain(){ static int jobs[20][20],flag[10]; int
ch; static int i,k,nj,nb,tms; clrscr(); printf("Enter time"); /*
reading time */ scanf("%d",&tms); printf("Enter no. of jobs");
/* reading no of jobs */ scanf("%d",&nj); printf("Enter job
information 1.jobid 2.jobsize"); for(i=0;inc=0;
if((*root)->nc==0) gap=rx-lx; else gap=(rx-lx)/(*root)->nc;
for(i=0;inc;i++)
create(&((*root)->link[i]),lev+1,(*root)->name,lx+gap*i,lx+gap*i+gap,lx+gap*i+gap/2);}else
(*root)->nc=0;} } display(node *root) { int i;
settextstyle(2,0,4); settextjustify(1,1); setfillstyle(1,BLUE);
setcolor(14); if(root!=NULL)
{for(i=0;inc;i++){line(root->x,root->y,root->link[i]->x,root->link[i]->y);}
if(root->ftype==1)bar3d(root->x-20,
root->y-10,root->x+20,root->y+10,0,0);elsefillellipse(root->x,root->y,20,20);outtextxy(root->x,root->y,root->name);for(i=0;inc;i++){display(root->link[i]);}
} }
7. Simulate Bankers algorithm for deadlock avoidanceAim: To
simulate bankers algorithm for deadlock
avoidanceDescription:Deadlock DefinitionA set of processes is
deadlocked if each process in the set is waiting for an event that
only another process in the set can cause (including itself).
Waiting for an event could be: waiting for access to a critical
section waiting for a resource Note that it is usually a
non-preemptable (resource). Preemptable resources can be yanked
away and given to another. Conditions for Deadlock Mutual
exclusion: resources cannot be shared. Hold and wait: processes
request resources incrementally, and hold on to what they've got.
No preemption : resources cannot be forcibly taken from processes.
Circular wait: circular chain of waiting, in which each process is
waiting for a resource held by the next process in the chain.
Strategies for dealing with Deadlock ignore the problem altogether
detection and recovery avoidance by careful resource allocation
prevention by structurally negating one of the four necessary
conditions. Deadlock AvoidanceAvoid actions that may lead to a
deadlock. Think of it as a state machine moving from one state to
another as each instruction is executed.
Safe StateSafe state is one where It is not a deadlocked
state
BANKERS ALGORITHM FOR DEADLOCK AVOIDANCE#include#includemain(){
int
a[10][10],c[10][10],r[10],av[10],ca[10][10],i,j,k,n,m,temp=0,tem,ch;
clrscr(); printf("enter no processes"); scanf("%d",&m);
printf("enter no of resources"); scanf("%d",&n);
printf("\nenter claim\n"); for(i=0;i
