The banker algorithm determines how to allocate resources by dynamically detecting the resource allocation in the system and the demand for resources by the process. When the system is in a safe state, the resources can be allocated to the applicant, thereby avoiding system deadlock.

Example:

Considering a system with five processes P₀ through P₄ and three resources of type A, B, C. Resource type A has 10 instances, B has 5 instances and type C has 7 instances. Suppose at time t₀ following snapshot of the system has been taken:

Process    Allocation    Max     Available

A,B,C           A,B,C       A,B,C

P0             0,1,0             7,5,3         3,3,2

P1             2,0,0            3,2,2

P2             3,0,2            9,0,2

P3             2,1,1            2,2,2

P1             0,0,2            4,3,3

Code:
#include <stdio.h>
int main()
{
// P0, P1, P2, P3, P4 are the Process names here

int n, m, i, j, k;
n = 5; // Number of processes
m = 3; // Number of resources
int alloc[5][3] = { { 0, 1, 0 }, // P0
{ 2, 0, 0 }, // P1
{ 3, 0, 2 }, // P2
{ 2, 1, 1 }, // P3
{ 0, 0, 2 } }; // P4

int max[5][3] = { { 7, 5, 3 }, // P0
{ 3, 2, 2 }, // P1
{ 9, 0, 2 }, // P2
{ 2, 2, 2 }, // P3
{ 4, 3, 3 } }; // P4

int avail[3] = { 3, 3, 2 }; // Available Resources

int f[n], ans[n], ind = 0;
for (k = 0; k < n; k++) {
f[k] = 0;
}
int need[n][m];
for (i = 0; i < n; i++) {
for (j = 0; j < m; j++)
need[i][j] = max[i][j] - alloc[i][j];
}
int y = 0;
for (k = 0; k < 5; k++) {
for (i = 0; i < n; i++) {
if (f[i] == 0) {

int flag = 0;
for (j = 0; j < m; j++) {
if (need[i][j] > avail[j]){
flag = 1;
break;
}
}

if (flag == 0) {
ans[ind++] = i;
for (y = 0; y < m; y++)
avail[y] += alloc[i][y];
f[i] = 1;
}
}
}
}

printf("Following is the SAFE Sequence\n");
for (i = 0; i < n - 1; i++)
printf(" P%d ->", ans[i]);
printf(" P%d", ans[n - 1]);

return (0);

// This code is contributed by Deep Baldha (CandyZack)
}

Output:

Following is the SAFE Sequence

P1 -> P3 -> P4 -> P0 -> P2