# Implementation of Priority scheduling (Non Pre-emptive) algorithm using C++

In this article, we are going to learn about **priority scheduling algorithm (non pre-emptive) and implementing this algorithm using C++ program**.

Submitted by Aleesha Ali, on January 29, 2018

**Non pre-emptive:** We cannot remove a process until it completes it execution.

Scheduling criteria tells us that any algorithm is how much efficient, the main criteria of scheduling are given below:

- CPU Utilization
- Throughput
- Arrival time
- Turnaround time
- Waiting time
- Completion time
- Burst time

*Ready Queue is a queue where all the processes wait to get CPU for its execution.

**CPU Utilization:** The amount of time CPU is busy.

**Throughput:** The number of process computed per unit time.

**Arrival time:** The time at which the process enters into ready queue.

**Turn around time:** The interval between the time of submission of a process to the time of completion.

**Waiting time:** The total amount of the time a process spends in ready queue.

**Completion time:** The time at which process completes its execution.

**Burst time:** The time needed by CPU to completes its execution.

## Priority Scheduling Algorithm (Non Pre-emptive)

In this algorithm priority is defined by manufacture of operating system, sometimes we assume minimum number has higher priority or vice a versa.

In my algorithm I use higher number has higher priority means process having higher priority will be schedule first.

## C++ Program for Priority Algorithm (Non-preemptive)

//Implementation of Priority(Non-Preeemptive) Using C++ #include <iostream> #include <algorithm> using namespace std; typedef struct proccess { int at,bt,pr,ct,ta,wt; string pro_id; /* artime = Arrival time, bt = Burst time, ct = Completion time, ta = Turn around time, wt = Waiting time */ }process; bool compare(process a,process b) { return a.at<b.at; /* This schedule will always return TRUE if above condition comes*/ } bool compare2(process a,process b) { return a.pr>b.pr; /* This schedule will always return TRUE if above condition comes*/ } int main() { process pro[10]; int n,i,j; cout<<"Enter the number of process::"; cin>>n; cout<<"Enter the process id arrival time burst time and priority :::"; for(i=0;i<n;i++) { cin>>pro[i].pro_id; cin>>pro[i].at; cin>>pro[i].bt; cin>>pro[i].pr; } sort(pro,pro+n,compare); /*sort is a predefined funcion defined in algorithm.h header file, it will sort the schedulees according to their arrival time*/ pro[0].ct=pro[0].bt+pro[0].at; pro[0].ta=pro[0].ct-pro[0].at; pro[0].wt=pro[0].ta-pro[0].bt; i=1; while(i<n-1) { for(j=i;j<n;j++) { if(pro[j].at>pro[i-1].ct) break; } sort(pro+i,pro+i+(j-i),compare2); pro[i].ct=pro[i-1].ct+pro[i].bt; pro[i].ta=pro[i].ct-pro[i].at; pro[i].wt=pro[i].ta-pro[i].bt; i++; } pro[i].ct=pro[i-1].ct+pro[i].bt; pro[i].ta=pro[i].ct-pro[i].at; pro[i].wt=pro[i].ta-pro[i].bt; for(i=0;i<n;i++) { //desplaying all the values cout<<pro[i].pro_id<<"\t"<<pro[i].at<<"\t"<<pro[i].bt<<"\t"<<pro[i].ct<<"\t"<<pro[i].ta<<"\t"<<pro[i].wt<<"\t"<<pro[i].pr; cout<<endl; } return 0; }

**Output**

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