Created fcfs.c

process_scheduling_algorithms/fcfs.c

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+/**
+ * @file
+ * @brief 
+ * [First-Come, First-Served (FCFS) Scheduling Algorithm]
+ * (https://en.wikipedia.org/wiki/Scheduling_(computing))
+ *
+ * @details
+ * This is a non-preemptive scheduling algorithm where the process that arrives
+ * first gets executed first. It is one of the simplest CPU scheduling algorithms.
+ * @author [Nivedh TJ](https://github.com/NivedhTJ)
+ */
+
+#include <stdio.h>  /// /// for IO operations (`printf`)
+#include <stdlib.h> /// for malloc, free
+#include <assert.h> /// for assert
+
+/**
+ * @brief Struct representing a process in the scheduling algorithm
+ */
+typedef struct
+{
+    int id;               ///< Process ID
+    int arrival_time;     ///< Time at which the process arrives
+    int burst_time;       ///< Time required by the process to complete
+    int completion_time;  ///< Time at which process completes execution
+    int turnaround_time;  ///< Turnaround time = completion - arrival
+    int waiting_time;     ///< Waiting time = turnaround - burst
+} process;
+
+/**
+ * @brief Comparator function for sorting processes by arrival time
+ * @param a Pointer to first process
+ * @param b Pointer to second process
+ * @return Negative if a comes before b, positive if b comes before a
+ */
+int compare_by_arrival(const void *a, const void *b)
+{
+    return ((process *)a)->arrival_time - ((process *)b)->arrival_time;
+}
+
+/**
+ * @brief Performs FIFO scheduling and calculates completion, turnaround, and waiting times
+ * @param processes Array of processes
+ * @param n Number of processes
+ */
+void calculate_fcfs_timings(process *processes, int n)
+{
+    qsort(processes, n, sizeof(process), compare_by_arrival);
+
+    int current_time = 0;
+    for (int i = 0; i < n; i++)
+    {
+        // Makes sure CPU waits if the next process hasn't arrived yet
+        if (current_time < processes[i].arrival_time)
+        {
+            current_time = processes[i].arrival_time;
+        }
+        processes[i].completion_time = current_time + processes[i].burst_time;
+        current_time = processes[i].completion_time;
+
+        processes[i].turnaround_time = processes[i].completion_time - processes[i].arrival_time;
+        processes[i].waiting_time = processes[i].turnaround_time - processes[i].burst_time;
+    }
+}
+
+/**
+ * @brief Test function to verify FIFO scheduling logic
+ */
+static void test_fifo()
+{
+    process test_processes[3] = {
+        {1, 0, 4, 0, 0, 0},
+        {2, 1, 3, 0, 0, 0},
+        {3, 2, 1, 0, 0, 0}};
+
+    calculate_fcfs_timings(test_processes, 3);
+
+    // Expected waiting times: P1 = 0, P2 = 3, P3 = 5
+    assert(test_processes[0].waiting_time == 0);
+    assert(test_processes[1].waiting_time == 3);
+    assert(test_processes[2].waiting_time == 5);
+
+    // Expected turnaround times: P1 = 4, P2 = 6, P3 = 6
+    assert(test_processes[0].turnaround_time == 4);
+    assert(test_processes[1].turnaround_time == 6);
+    assert(test_processes[2].turnaround_time == 6);
+
+    printf("All test cases passed!\n");
+}
+
+
+/**
+ * @brief Main function
+ * @return 0 upon successful execution
+ */
+int main()
+{
+    test_fifo();
+    return 0;
+}