C program of Banker’s Algorithm to avoid Deadlock

Mr Coder August 29, 2012 11

C program of banker’s algorithm to avoid deadlock : Banker’s algorithm is a resource allocation and deadlock avoidance algorithm developed by Edsger Dijkstra that tests for safety by simulating the allocation of predetermined maximum possible amounts of all resources, and then makes a “s-state” check to test for possible deadlock conditions for all other pending activities, before deciding whether allocation should be allowed to continue.

How Banker’s Algorithm works ?

The Banker’s algorithm is run by the operating system whenever a process requests resources. The algorithm avoids deadlock by denying or postponing the request if it determines that accepting the request could put the system in an unsafe state (one where deadlock could occur). When a new process enters a system, it must declare the maximum number of instances of each resource type that may not exceed the total number of resources in the system. Also, when a process gets all its requested resources it must return them in a finite amount of time.

Let us see how to implement Banker’s algorithm in C which takes number of processes and resources as input shows state as output.

C program of Banker’s Algorithm to avoid deadlock :

```#include<stdio.h>
#include<conio.h>
int main()
{
int clm[7][5],req[7][5],alloc[7][5],rsrc[5],avail[5],comp[7];
int first,p,r,i,j,prc,count,t;
count=0;
for(i=1;i<=7;i++)
comp[i]=0;
printf("----------------------------------------------------\n");
printf("----------------------------------------------------\n\n");
printf("\t BANKERS ALGORITHM IN C \n\n");
printf("Enter the no of processes : ");
scanf("%d",&p);
printf("\n\nEnter the no of resources : ");
scanf("%d",&r);
printf("\n\nEnter the claim for each process : ");
for(i=1;i<=p;i++)
{
printf("\nFor process %d : ",i);
for(j=1;j<=r;j++)
{
scanf("%d",&clm[i][j]);
}
}
printf("\n\nEnter the allocation for each process : ");
for(i=1;i<=p;i++)
{
printf("\nFor process %d : ",i);
for(j=1;j<=r;j++)
{
scanf("%d",&alloc[i][j]);
}
}
printf("\n\nEnter total no of each resource : ");
for(j=1;j<=r;j++)
scanf("%d",&rsrc[j]);
for(j=1;j<=r;j++)
{
int total=0;
avail[j]=0;
for(i=1;i<=p;i++)
{total+=alloc[i][j];}
avail[j]=rsrc[j]-total;
}
do
{
for(i=1;i<=p;i++)
{
for(j=1;j<=r;j++)
{
req[i][j]=clm[i][j]-alloc[i][j];
}
}
printf("\n\nAvailable resources are : ");
for(j=1;j<=r;j++)
{ printf(" ",avail[j]); }
printf("\nClaim matrix:\tAllocation matrix:\n");
for(i=1;i<=p;i++)
{
for(j=1;j<=r;j++)
{
printf("%d\t",clm[i][j]);
}
printf("\t\t\t");
for(j=1;j<=r;j++)
{
printf("%d\t",alloc[i][j]);
}
printf("\n");
}
prc=0;
for(i=1;i<=p;i++)
{
if(comp[i]==0)//if not completed
{
prc=i;
for(j=1;j<=r;j++)
{
if(avail[j]=0)
{
prc=0;
break;
}
}
}
if(prc!=0)
break;
}
if(prc!=0)
{
printf("\nProcess ",prc,"runs to completion!");
count++;
for(j=1;j<=r;j++)
{
avail[j]+=alloc[prc][j];
alloc[prc][j]=0;
clm[prc][j]=0;
comp[prc]=1;
}
}
}
while(count!=p&&prc!=0);
if(count==p)
printf("\nThe system is in a safe state!!");
else
printf("\nThe system is in an unsafe state!!");
getch();
}```

We hope you all have enjoyed the above C program of Banker’s Algorithm to avoid deadlock. If you have any issues with above code or logic, ask us in form of comments.

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