Tag Archives: banker’s algorithm for deadlock prevention program in c

Banker’s Algorithm Implementation in C

Definition:

The Banker’s algorithm is a resource allocation and deadlock avoidance algorithm developed by Edsger Dijkstra.

Banker’s Algorithm working principle:

It 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.

Implementation in C :

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/* 
*	Banker's Algorithm
*  
*  Author 	: Rajesh Hegde
*	
*	Language	: C
*
*	compiler : gcc 
*
*/

/*<--------------PREPROCESSING STATEMENTS--------------->*/
#include <stdio.h>
#include <conio.h>

/*<--------------MAIN FUNCTION--------------->*/ 

int main()
{
int Max[10][10], need[10][10], alloc[10][10], avail[10], completed[10], safeSequence[10];
int p, r, i, j, process, count;
count = 0;

printf("Enter the no of processes : ");
scanf("%d", &p);

for(i = 0; i< p; i++)
	completed[i] = 0;

printf("\n\nEnter the no of resources : ");
scanf("%d", &r);

printf("\n\nEnter the Max Matrix for each process : ");
for(i = 0; i < p; i++)
{
	printf("\nFor process %d : ", i + 1);
	for(j = 0; j < r; j++)
		scanf("%d", &Max[i][j]);
}

printf("\n\nEnter the allocation for each process : ");
for(i = 0; i < p; i++)
{
	printf("\nFor process %d : ",i + 1);
	for(j = 0; j < r; j++)
		scanf("%d", &alloc[i][j]);	
}

printf("\n\nEnter the Available Resources : ");
for(i = 0; i < r; i++)
		scanf("%d", &avail[i]);	


	for(i = 0; i < p; i++)
		for(j = 0; j < r; j++)
			need[i][j] = Max[i][j] - alloc[i][j];
		
do
{
	printf("\n Max matrix:\tAllocation matrix:\n");
	for(i = 0; i < p; i++)
	{
		for( j = 0; j < r; j++)
			printf("%d  ", Max[i][j]);
		printf("\t\t");
		for( j = 0; j < r; j++)
			printf("%d  ", alloc[i][j]);
		printf("\n");
	}

	process = -1;

	for(i = 0; i < p; i++)
	{
		if(completed[i] == 0)//if not completed
		{
			process = i ;
			for(j = 0; j < r; j++)
			{
				if(avail[j] < need[i][j])
				{
					process = -1;
					break;
				}
			}
		}
		if(process != -1)
			break;
	}

	if(process != -1)
	{
		printf("\nProcess %d runs to completion!", process + 1);
		safeSequence[count] = process + 1;
		count++;
		for(j = 0; j < r; j++)
		{
			avail[j] += alloc[process][j];
			alloc[process][j] = 0;
			Max[process][j] = 0;
			completed[process] = 1;
		}
	}
}while(count != p && process != -1);

if(count == p)
{
	printf("\nThe system is in a safe state!!\n");
	printf("Safe Sequence : < ");
	for( i = 0; i < p; i++)
			printf("%d  ", safeSequence[i]);
	printf(">\n");
}
else
	printf("\nThe system is in an unsafe state!!");
getch();
}