Resource-Request Algorithm for Process Pi

   Request = request vector for process Pi.  If Requesti [j] = k then process Pi wants k instances of resource type Rj.

1.  If Requesti £ Needi go to step 2.  Otherwise, raise error condition, since process has exceeded its maximum claim.

2.  If Requesti £ Available, go to step 3.  Otherwise Pi  must wait, since resources are not available.

3.  Pretend to allocate requested resources to Pi by modifying the state as follows:

  Available = Available = Requesti;

  Allocationi = Allocationi + Requesti;

  Needi = Needi – Requesti;;

•If safe Þ the resources are allocated to Pi.

•If unsafe Þ Pi must wait, and the old resource-allocation state is restored