diff --git a/Operating Systems/CPU Scheduling Algorithms/FirstComeFirstServe.c b/Operating Systems/CPU Scheduling Algorithms/FirstComeFirstServe.c
new file mode 100644
index 00000000..762d3bff
--- /dev/null
+++ b/Operating Systems/CPU Scheduling Algorithms/FirstComeFirstServe.c	
@@ -0,0 +1,39 @@
+#include <stdio.h>
+int main()
+{
+    char pn[10][10];
+    int arr[10], bur[10], star[10], finish[10], tat[10], wt[10], i, n;
+    int totwt=0, tottat=0;
+    printf("Enter the number of processes: ");
+    scanf("%d",&n);
+    for(i=0;i<n;i++)
+    {
+        printf("Enter the Process Name, Arrival Time & Burst Time: ");
+        scanf("%s%d%d",&pn[i],&arr[i],&bur[i]);
+    }
+    for(i=0;i<n;i++) {
+        if(i==0)
+        {
+            star[i]=arr[i];
+            wt[i]=star[i]-arr[i];
+            finish[i]=star[i]+bur[i];
+            tat[i]=finish[i]-arr[i];
+        }
+        else
+        {
+            star[i]=finish[i-1];
+            wt[i]=star[i]-arr[i];
+            finish[i]=star[i]+bur[i];
+            tat[i]=finish[i]-arr[i];
+        }
+    }
+    printf("\nPName\tArrtime\t\tBurtime\t\t Start\t\t TAT\t\tFinish");
+    for(i=0;i<n;i++)
+    {
+        printf("\n%s\t%6d\t\t%6d\t\t%6d\t\t%6d\t\t%6d",pn[i],arr[i],bur[i],star[i],tat[i],finish[i]);
+        totwt+=wt[i];
+        tottat+=tat[i];
+    }
+    printf("\nAverage Waiting time:%f", (float)totwt/3);
+    printf("\nAverage Turn Around Time:%f\n", (float)tottat/3);
+}
\ No newline at end of file
diff --git a/Operating Systems/CPU Scheduling Algorithms/Priority.c b/Operating Systems/CPU Scheduling Algorithms/Priority.c
new file mode 100644
index 00000000..b50595ae
--- /dev/null
+++ b/Operating Systems/CPU Scheduling Algorithms/Priority.c	
@@ -0,0 +1,61 @@
+#include <stdio.h>
+#include <stdlib.h>
+#define MAX_PROCESSES 10
+typedef struct
+{
+    int pid; // process ID
+    int burst_time; // burst time (in milliseconds)
+    int priority; // priority (higher number means higher priority)
+    int waiting_time; // waiting time (in milliseconds)
+    int turnaround_time; // turnaround time (in milliseconds)
+} Process;
+int main()
+{
+    Process processes [MAX_PROCESSES];
+    int num_processes, i, j;
+    printf("Enter the number of processes: ");
+    scanf("%d", &num_processes);
+    for (i = 0; i < num_processes; i++) {
+        printf("\nEnter the burst time for process %d (in milliseconds): ", i+1);
+        scanf("%d", &processes[i].burst_time);
+        printf("Enter the priority for process %d (higher number means higher priority): ", i+1);
+        scanf("%d", &processes[i].priority);
+        processes[i].pid = i+1;
+    }
+    for (i = 0; i < num_processes - 1; i++)
+    {
+        for (j = i+1; j < num_processes; j++)
+        {
+            if (processes[i].priority < processes[j].priority)
+            {
+                Process temp = processes[i];
+                processes[i] = processes[j];
+                processes[j] = temp;
+        }
+        }
+    }
+    int total_waiting_time = 0, total_turnaround_time = 0;
+    for (i = 0; i < num_processes; i++)
+    {
+        if (i == 0)
+        {
+            processes[i].waiting_time = 0;
+        }
+        else
+        {
+            processes[i].waiting_time = processes[i-1].turnaround_time;
+        }
+        processes[i].turnaround_time = processes[i].waiting_time + processes[i].burst_time;
+        total_waiting_time += processes[i].waiting_time;
+        total_turnaround_time += processes[i].turnaround_time;
+    }
+    printf("\nPID\tBurst Time\tPriority\tWaiting Time\tTurnaround Time\n");
+    for (i = 0; i < num_processes; i++)
+    {
+        printf("%d\t%d ms\t\t%d\t\t%d ms\t\t%d ms\n", processes[i].pid, processes[i].burst_time, processes[i].priority, processes[i].waiting_time, processes[i].turnaround_time);
+    }
+    printf("\nAverage waiting time: %.2f ms", (float)total_waiting_time/num_processes);
+    printf("\nAverage turnaround time: %.2f ms\n",
+    (float)total_turnaround_time/num_processes);
+    return 0;
+}
\ No newline at end of file
diff --git a/Operating Systems/CPU Scheduling Algorithms/RoundRobin.c b/Operating Systems/CPU Scheduling Algorithms/RoundRobin.c
new file mode 100644
index 00000000..5e35fb36
--- /dev/null
+++ b/Operating Systems/CPU Scheduling Algorithms/RoundRobin.c	
@@ -0,0 +1,57 @@
+#include<stdio.h>
+struct process {
+    int burst, wait, comp, f;
+} p[20]={0,0};
+int main( ) {
+    int n, i, j, totalwait=0, totalturn=0, quantum,flag=1, time=0;
+    printf("\nEnter the no. of processes: ");
+    scanf("%d",&n);
+    printf("\nEnter the Quantum time (in ms) : ");
+    scanf("%d",&quantum);
+    for(i=0;i<n;i++) {
+        printf("Enter the Burst Time (in ms) For Process #%2d : ",i+1);
+        scanf("%d",&p[i].burst);
+        p[i].f=1;
+    }
+    printf("\nOrder of Execution \n");
+    printf("\nProcess Starting Ending Remaining");
+    printf("\n\t\tTime\t Time \t\t Time");
+    while(flag==1)
+    {
+        flag=0;
+        for(i=0;i<n;i++)
+        {
+            if(p[i].f==1)
+            {
+                flag=1;
+                j=quantum;
+                if((p[i].burst-p[i].comp)>quantum)
+                {
+                    p[i].comp+=quantum;
+                }
+                else
+                {
+                    p[i].wait=time-p[i].comp;
+                    j=p[i].burst-p[i].comp;
+                    p[i].comp=p[i].burst;
+                    p[i].f=0;
+                }
+                printf("\nProcess # %-3d %-10d %-10d %-10d", i+1, time,
+                time+j, p[i].burst-p[i].comp);
+                time+=j;
+            }
+        }
+    }
+    printf("\n\n--------------------");
+    printf("\nProcess \t Waiting Time TurnAround Time ");
+    for(i=0;i<n;i++)
+    {
+        printf("\nProcess # %-12d%-15d%-15d",i+1,p[i].wait,p[i].wait+p[i].burst);
+        totalwait=totalwait+p[i].wait;
+        totalturn=totalturn+p[i].wait+p[i].burst;
+    }
+    printf("\n\nAverage\n-------------------");
+    printf("\nWaiting Time: %fms",totalwait/(float)n);
+    printf("\nTurnAround Time : %fms\n\n",totalturn/(float)n);
+    return 0;
+}
\ No newline at end of file
diff --git a/Operating Systems/CPU Scheduling Algorithms/ShortestJobFirst.c b/Operating Systems/CPU Scheduling Algorithms/ShortestJobFirst.c
new file mode 100644
index 00000000..4cb6b709
--- /dev/null
+++ b/Operating Systems/CPU Scheduling Algorithms/ShortestJobFirst.c	
@@ -0,0 +1,44 @@
+#include<stdio.h>
+#include<string.h>
+int main()
+{
+    int i=0, pno[10], bt[10], n, wt[10], temp=0, j, tt[10];
+    float sum,at;
+    printf("\nEnter the no. of process: ");
+    scanf("\n %d",&n);
+    printf("\nEnter the burst time of each process: \n");
+    for(i=0;i<n;i++)
+    {
+        printf("P%d ",i);
+        scanf("%d",&bt[i]);
+    }
+    for(i=0;i<n-1;i++)
+    {
+        for(j=i+1;j<n;j++)
+        {
+            if(bt[i]>bt[j])
+            {
+                temp=bt[i];
+                bt[i]=bt[j];
+                bt[j]=temp;
+                temp=pno[i];
+                pno[i]=pno[j];
+                pno[j]=temp;
+            }
+        }
+    }
+    wt[0]=0;
+    for(i=1;i<n;i++)
+    {
+        wt[i]=bt[i-1]+wt[i-1];
+        sum=sum+wt[i];
+    }
+    printf("\nProcess No \t Burst Time\t Waiting time \t Turn around time\n");
+    for(i=0;i<n;i++)
+    {
+        tt[i]=bt[i]+wt[i];
+        at+=tt[i];
+        printf("\n P%d\t\t %d\t\t %d\t\t %d",i,bt[i],wt[i],tt[i]);
+    }
+    printf("\n\nAverage waiting time: %f\nAverage turn around time: %f\n", sum/n, at/n);
+}
\ No newline at end of file
diff --git a/Operating Systems/Memory Allocation Methods/BestFit.c b/Operating Systems/Memory Allocation Methods/BestFit.c
new file mode 100644
index 00000000..7532ea76
--- /dev/null
+++ b/Operating Systems/Memory Allocation Methods/BestFit.c	
@@ -0,0 +1,52 @@
+#include<stdio.h>
+void main() {
+    int a[20], p[20], i, j, n, m, temp, b[20], temp1, temp2, c[20];
+    printf("\nMEMORY MANAGEMENT SCHEME - BEST FIT \n");
+    printf("Enter No. of Blocks: ");
+    scanf("%d",&n);
+    for(i=0;i<n;i++) {
+        printf("Enter the %dst block size: ",i);
+        scanf("%d",&a[i]);
+    }
+    printf("Enter No. of Process: ");
+    scanf("%d",&m);
+    for(i=0;i<m;i++)
+    {
+        printf("Enter the size of %dst process: ",i);
+        scanf("%d",&p[i]);
+    }
+    for(i=0;i<n;i++)
+    {
+        for(j=0;j<m;j++)
+        {
+            if(a[i]>a[j])
+            {
+                temp=a[i];
+                a[i]=a[j];
+                a[j]=temp;
+            }
+            if(p[i]>p[j])
+            {
+                temp=p[i];
+                p[i]=p[j];
+                p[j]=temp;
+            }
+        }
+    }
+    printf("\nProcess\tBlock Size\n");
+    for(i=0;i<n;i++)
+        printf("%d\t%d\n",p[i],a[i]);
+    printf("\n\n");
+    for(i=0;i<n;i++) {
+        for(j=0;j<m;j++) {
+            if(p[j]<=a[i]) {
+                printf("The process %d [size %d] allocated to block %d\n", j, p[j], a[i]);
+                p[j]=10000;
+                break;
+            }
+        }
+    }
+    for(j=0;j<m;j++)
+        if(p[j]!=10000)
+            printf("The process %d is not allocated\n",p[j]);
+}
\ No newline at end of file
diff --git a/Operating Systems/Memory Allocation Methods/FirstFit.c b/Operating Systems/Memory Allocation Methods/FirstFit.c
new file mode 100644
index 00000000..387f98d5
--- /dev/null
+++ b/Operating Systems/Memory Allocation Methods/FirstFit.c	
@@ -0,0 +1,38 @@
+#include<stdio.h>
+void main()
+{
+    int a[20], p[20], i, j, n, m, temp, b[20], temp1, temp2, c[20];
+    printf("\nMEMORY MANAGEMENT SCHEME - FIRST FIT \n");
+    printf("Enter No. of Blocks: ");
+    scanf("%d",&n);
+    for(i=0;i<n;i++)
+    {
+        printf("Enter the %dst block size: ",i);
+        scanf("%d",&a[i]);
+    }
+    printf("Enter No. of Process: ");
+    scanf("%d",&m);
+    for(i=0;i<m;i++)
+    {
+        printf("Enter the size of %dst process: ",i);
+        scanf("%d",&p[i]);
+    }
+    printf("\nProcess\tBlock Size\n");
+    for(i=0;i<n;i++)
+        printf("%d\t\t%d\n",p[i],a[i]);
+    printf("\n\n");
+    for(i=0;i<n;i++)
+    {
+        for(j=0;j<m;j++)
+        {
+            if(p[j]<=a[i])
+            {
+                printf("The process %d [size %d] allocated to block %d\n",j,p[j],a[i]);
+                p[j]=10000; break;
+            }
+        }
+    }
+    for(j=0;j<m;j++)
+        if(p[j]!=10000)
+            printf("The process %d is not allocated\n",j);
+}
\ No newline at end of file
diff --git a/Operating Systems/Memory Allocation Methods/WorstFit.c b/Operating Systems/Memory Allocation Methods/WorstFit.c
new file mode 100644
index 00000000..f5b9f1c6
--- /dev/null
+++ b/Operating Systems/Memory Allocation Methods/WorstFit.c	
@@ -0,0 +1,54 @@
+#include<stdio.h>
+void main()
+{
+    int a[20], p[20], i, j, n, m, temp, b[20], temp1, temp2, c[20];
+    printf("\nMEMORY MANAGEMENT SCHEME - WORST FIT \n");
+    printf("Enter No. of Blocks: ");
+    scanf("%d",&n);
+    for(i=0;i<n;i++)
+    {
+        printf("Enter the %dst block size: ",i);
+        scanf("%d",&a[i]);
+    }
+    printf("Enter No. of Process: ");
+    scanf("%d",&m);
+    for(i=0;i<m;i++)
+    {
+        printf("Enter the size of %dst process: ",i);
+        scanf("%d",&p[i]);
+    }
+    for(i=0;i<n;i++)
+    {
+        for(j=0;j<m;j++)
+        {
+            if(a[i]>a[j])
+            {
+                temp=a[i];
+                a[i]=a[j];
+                a[j]=temp;
+            }
+            if(p[i]<p[j])
+            {
+                temp=p[i];
+                p[i]=p[j];
+                p[j]=temp;
+            }
+        }
+    }
+    printf("\nProcess\tBlock Size\n");
+    for(i=0;i<n;i++)
+        printf("%d\t%d\n",p[i],a[i]);
+    printf("\n\n");
+    for(i=0;i<n;i++) {
+        for(j=0;j<m;j++) {
+            if(p[j]<=a[i]) {
+                printf("The process %d [size %d] allocated to block %d\n",j,p[j],a[i]);
+                p[j]=10000;
+                break;
+            }
+        }
+    }
+    for(j=0;j<m;j++)
+        if(p[j]!=10000)
+            printf("The process %d is not allocated\n",p[j]);
+}
\ No newline at end of file
diff --git a/Operating Systems/Page Replacement Algorithms/FirstInFirstOut.c b/Operating Systems/Page Replacement Algorithms/FirstInFirstOut.c
new file mode 100644
index 00000000..f92ae450
--- /dev/null
+++ b/Operating Systems/Page Replacement Algorithms/FirstInFirstOut.c	
@@ -0,0 +1,34 @@
+#include<stdio.h>
+void main() {
+    int a[5], b[20], n, p=0, q=0, m=0, h, k, i, q1=1;
+    char f='F';
+    printf("Enter the Number of Pages: ");
+    scanf("%d",&n);
+    printf("Enter %d Page Numbers: ",n);
+    for(i=0;i<n;i++)
+        scanf("%d",&b[i]);
+    for(i=0;i<n;i++) {
+        if(p==0) {
+            if(q>=3)
+                q=0;
+            a[q]=b[i]; q++;
+            if(q1<3) {
+                q1=q;
+            }
+        }
+        printf("\n%d",b[i]);
+        printf("\t");
+        for(h=0;h<q1;h++)
+            printf("%d",a[h]);
+        if((p==0)&&(q<=3)) {
+            printf("-->%c",f);
+            m++;
+        }
+        p=0;
+        for(k=0;k<q1;k++) {
+            if(b[i+1]==a[k])
+                p=1;
+        } 
+    }
+    printf("\nNo of faults: %d\n",m);
+}
\ No newline at end of file
diff --git a/Operating Systems/Page Replacement Algorithms/LeastRecentlyUsed.c b/Operating Systems/Page Replacement Algorithms/LeastRecentlyUsed.c
new file mode 100644
index 00000000..d52b3c51
--- /dev/null
+++ b/Operating Systems/Page Replacement Algorithms/LeastRecentlyUsed.c	
@@ -0,0 +1,61 @@
+#include<stdio.h>
+int main()
+{
+    int a[5], b[20], p=0, q=0, m=0, h, k, i, q1=1, j, u, n;
+    char f='F';
+    printf("Enter the number of pages: ");
+    scanf("%d",&n);
+    printf("Enter %d Page Numbers: ",n);
+    for(i=0;i<n;i++)
+        scanf("%d",&b[i]);
+    for(i=0;i<n;i++) {
+        if(p==0) {
+            if(q>=3)
+                q=0;
+            a[q]=b[i];
+            q++;
+            if(q1<3)
+                q1=q;
+        }
+        printf("\n%d",b[i]);
+        printf("\t");
+        for(h=0;h<q1;h++)
+            printf("%d",a[h]);
+        if((p==0)&&(q<=3))
+        {
+            printf("-->%c",f);
+            m++;
+        }
+        p=0;
+        if(q1==3)
+        {
+            for(k=0;k<q1;k++)
+            {
+                if(b[i+1]==a[k])
+                p=1;
+            }
+            for(j=0;j<q1;j++)
+            {
+                u=0;
+                k=i;
+                while(k>=(i-1)&&(k>=0))
+                {
+                    if(b[k]==a[j])
+                    u++;
+                    k--;
+                }
+                if(u==0)
+                    q=j;
+            }
+        }
+        else
+        {
+            for(k=0;k<q;k++)
+            {
+                if(b[i+1]==a[k])
+                p=1;
+            }
+        }
+    }
+    printf("\nNo of faults: %d\n",m);
+}
\ No newline at end of file
diff --git a/Operating Systems/Page Replacement Algorithms/Optimal.c b/Operating Systems/Page Replacement Algorithms/Optimal.c
new file mode 100644
index 00000000..ebcb8103
--- /dev/null
+++ b/Operating Systems/Page Replacement Algorithms/Optimal.c	
@@ -0,0 +1,63 @@
+#include <stdio.h>
+#include <stdlib.h>
+#define MAX_PAGES 100
+#define MAX_FRAMES 10
+int main()
+{
+    int pages[MAX_PAGES], frames[MAX_FRAMES];
+    int num_pages, num_frames, num_hits = 0, num_misses = 0;
+    int i, j, k, pos, max_pos, max_dist;
+    printf("Enter the number of pages: ");
+    scanf("%d", &num_pages);
+    printf("Enter the page references: ");
+    for (i = 0; i < num_pages; i++) {
+        scanf("%d", &pages[i]);
+    }
+    printf("Enter the number of frames: ");
+    scanf("%d", &num_frames);
+    for (i = 0; i < num_frames; i++) {
+        frames[i] = -1;
+    }
+    for (i = 0; i < num_pages; i++) {
+        for (j = 0; j < num_frames; j++) {
+            if (frames[j] == pages[i]) {
+                num_hits++;
+                break;
+            }
+        }
+        if (j == num_frames)
+        {
+            num_misses++;
+            max_pos = -1;
+            max_dist = -1;
+            for (j = 0; j < num_frames; j++)
+            {
+                pos = -1;
+                for (k = i+1; k < num_pages; k++)
+                {
+                    if (frames[j] == pages[k])
+                    {
+                        pos = k;
+                        break;
+                    }
+                }
+                if (pos == -1)
+                {
+                    max_pos = j;
+                    break;
+                }
+                else if (pos > max_dist)
+                {
+                    max_pos = j;
+                    max_dist = pos;
+                }
+            }
+            frames[max_pos] = pages[i];
+        }
+    }
+    printf("Number of page hits: %d\n", num_hits);
+    printf("Number of page misses: %d\n", num_misses);
+    printf("Hit ratio: %.2f\n", (float)num_hits/num_pages);
+    printf("Miss ratio: %.2f\n", (float)num_misses/num_pages);
+    return 0;
+}
\ No newline at end of file