# Implementation of Shortest Job First (SJF) Preemptive CPU scheduling algorithm using C++

In this article, we are going to learn about **implementation of shortest job first (SJF) preemptive scheduling algorithm using C++ program**.

Submitted by Aleesha Ali, on January 29, 2018

**Preemptive:** If a process of higher priority comes then first CPU will be assign to the Process with higher priority first.

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

* 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.

**Turnaround time:** The interval between the times 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 complete its execution.

## SORTEST JOB FIRST (Preemptive)

This algorithm also known as **SRTF (Shortest Remaining Time First)**. As this algorithm is preemptive so the process having minimum arrival time will execute first and after this normal SJF (SHORTEST JOB FIRST) will be follow.

## C++ Program for SJF (Preemptive) scheduling:

//Implementation fo SHORTEST JOB FIRST(Preemptive) Using C++ #include <iostream> #include <algorithm> #include <cstring> using namespace std; typedef struct proccess { int at,bt,ct,ta,wt,btt; string pro_id; /* artime = Arrival time, bt = Burst time, ct = Completion time, ta = Turn around time, wt = Waiting time */ }Schedule; bool compare(Schedule a,Schedule b) { return a.at<b.at; /* This Schedule will always return TRUE if above condition comes*/ } bool compare2(Schedule a,Schedule b) { return a.bt<b.bt; /* This Schedule will always return TRUE if above condition comes*/ } int main() { Schedule pro[10]; //An array of Processes int n,i,j,pcom; //n = number of processes, i= iteration variable cout<<"Enter the number of Process::"; cin>>n; cout<<"Enter the Process id arrival time burst time :::"; for(i=0;i<n;i++) { cin>>pro[i].pro_id; cin>>pro[i].at; cin>>pro[i].bt; pro[i].btt=pro[i].bt; } sort(pro,pro+n,compare); /*sort is a predefined funcion defined in algorithm.h header file, it will sort the processes according to their arrival time*/ i=0; pcom=0; while(pcom<n) { for(j=0;j<n;j++) { if(pro[j].at>i) break; } sort(pro,pro+j,compare2); /*sort is a predefined funcion defined in algorithm.h header file, it will sort the processes according to their burst time*/ if(j>0) { for(j=0;j<n;j++) { if(pro[j].bt!=0) break; } if(pro[j].at>i) { i=pro[j].at; } pro[j].ct=i+1; pro[j].bt--; } i++; pcom=0; for(j=0;j<n;j++) { if(pro[j].bt==0) pcom++; } } cout<<"ProID\tAtime\tBtime\tCtime\tTtime\tWtime\n"; for(i=0;i<n;i++) { pro[i].ta=pro[i].ct-pro[i].at; pro[i].wt=pro[i].ta-pro[i].btt; /*Printing the Process id, arrival time, burst time, completion time, turn around time, waiting time*/ cout<<pro[i].pro_id<<"\t"<<pro[i].at<<"\t"<<pro[i].btt<<"\t"<<pro[i].ct<<"\t"<<pro[i].ta<<"\t"<<pro[i].wt; cout<<endl; } return 0; }

**Output**

Related Tutorials

- Introduction to Algorithms
- Introduction to Greedy Strategy in Algorithms
- Stability in sorting
- External Merge Sorting Algorithm
- Radix Sort and its Algorithm
- Bucket Sort Algorithm
- Bubble sort Algorithm, Flow Chart and C++ Code
- Insertion sort Algorithm, flowchart and C, C++ Code
- Merge Sort | One of the best sorting algorithms used for large inputs
- Binary Search in C, C++
- Randomized Binary Search
- Meta Binary Search | One-sided Binary Search
- Difference between Linear Search and Binary Search
- Binary Search in String
- Variants of Binary Search
- Sieve of Eratosthenes to find prime numbers
- Optimal Merge Pattern (Algorithm and Example)
- Given an array of n numbers, Check whether there is any duplicate or not
- Finding the missing number
- Find the number occurring an odd number of times
- Find the pair whose sum is closest to zero in minimum time complexity
- Find three elements in an array such that their sum is equal to given element K
- Bitonic Search Algorithm
- Check whether a number is Fibonacci or not
- Segregate even and odd numbers in minimum time complexity
- Find trailing zeros in factorial of a number
- Find Nearest Greatest Neighbours of each element in an array
- Interpolation search algorithm
- Floor and ceil of an element in an array using C++
- Two Elements whose sum is closest to zero
- Find a pair with a given difference
- Count number of occurrences (or frequency) in a sorted array
- Find a Fixed Point (Value equal to index) in a given array
- Find the maximum element in an array which is first increasing and then decreasing
- Dynamic Programming (Components, Applications and Elements)
- Algorithm for fractional knapsack problem
- Algorithm and procedure to solve a longest common subsequence problem
- Find the Nth Fibonacci number | C++
- Longest Common Subsequence using Dynamic programming (DP)
- Longest Increasing Subsequence using Dynamic programming (DP)
- Find the maximum sub-array sum using KADANE'S ALGORITHM
- Non-intersecting chords using Dynamic Programming (DP)
- Edit Distance using Dynamic Programming (DP)
- Finding Ugly Number using Dynamic Programming (DP)
- Egg dropping problem using Dynamic Programming (DP)
- Wild card matching problem using Dynamic programming (DP)
- Compute sum of digits in all numbers from 1 to N for a given N
- Minimum jumps required using Dynamic programming (DP)
- Graph coloring problem's solution using backtracking algorithm
- Breadth First Search (BFS) and Depth First Search (DFS) Algorithms
- Travelling Salesman Problem
- Kruskal's (P) and Prim's (K) Algorithms
- Multistage graph problem with forward approach and backward approach algorithms
- Floyd Warshall algorithm with its Pseudo Code

- Backtracking (Types and Algorithms)
- 4 Queen's problem and solution using backtracking algorithm
- N Queen's problem and solution using backtracking algorithm
- Find the GCD (Greatest Common Divisor) of two numbers using EUCLID'S ALGORITHM
- Compute the value of A raise to the power B using Fast Exponentiation
- Implement First Come First Served (FCFS) CPU Scheduling Algorithm using C program
- Implementations of FCFS scheduling algorithm using C++
- Implementation of Shortest Job First (SJF) Non-Preemptive CPU scheduling algorithm using C++
- Implementation of Shortest Job First (SJF) Preemptive CPU scheduling algorithm using C++
- Implementation of Priority scheduling (Pre-emptive) algorithm using C++
- Implementation of Round Robin CPU Scheduling algorithm using C++
- Analysis of LRU page replacement algorithm and Belady's anomaly
- Branch and Bound
- Find the roots of a complex polynomial equation using Regula Falsi Method in C
- Sieve of Eratosthenes to find prime numbers
- Implementations of FCFS scheduling algorithm using C++
- Implementation of Shortest Job First (SJF) Non-Preemptive CPU scheduling algorithm using C++
- Implementation of Shortest Job First (SJF) Preemptive CPU scheduling algorithm using C++
- Implementation of Priority scheduling (Pre-emptive) algorithm using C++
- Divide and Conquer Paradigm (What it is, Its Applications, Pros and Cons)
- Implementation of Priority scheduling (Non Pre-emptive) algorithm using C++
- Implementation of Round Robin CPU Scheduling algorithm using C++
- Jump Search Implementation using C++
- Optimal Merge Pattern (Algorithm and Example)
- Introduction to Greedy Strategy in Algorithms
- Strassen's Matrix Multiplication in algorithms
- Huffman Coding (Algorithm, Example and Time complexity)
- Backtracking (Types and Algorithms)
- 4 Queen's problem and solution using backtracking algorithm
- N Queen's problem and solution using backtracking algorithm
- Graph coloring problem's solution using backtracking algorithm
- Tournament Tree and their properties
- Deterministic and Non Deterministic Algorithms
- Lower Bound Theory
- Non Recursive Tree Traversal Algorithm
- Line Drawing Algorithm
- Breadth First Search (BFS) and Depth First Search (DFS) Algorithms
- P and NP problems and solutions | Algorithms
- Travelling Salesman Problem
- 2 – 3 Trees Algorithm
- Kruskal's (P) and Prim's (K) Algorithms
- Algorithm for fractional knapsack problem
- Algorithm and procedure to solve a longest common subsequence problem
- Midpoint Circle Algorithm
- Multistage graph problem with forward approach and backward approach algorithms
- Floyd Warshall algorithm with its Pseudo Code
- Reliability design problem
- Removing consecutive duplicates from a string
- Fast Exponentiation using Bitmasking

Comments and Discussions!