diff --git a/COHENSUTHERLAND_LINECLIPPING_ALGO.CPP b/COHENSUTHERLAND_LINECLIPPING_ALGO.CPP
index a115507..91e8951 100644
--- a/COHENSUTHERLAND_LINECLIPPING_ALGO.CPP
+++ b/COHENSUTHERLAND_LINECLIPPING_ALGO.CPP
@@ -4,6 +4,7 @@
 #include<graphics.h>
 #include<process.h>
 #include<dos.h>
+
 void main()
 {
 	int gd=DETECT,gm;
@@ -144,11 +145,3 @@ void main()
 	closegraph();
 	getch();
 }
-
-
-
-
-
-
-
-
diff --git a/Compiler_Design/lex_programs/abc.l b/Compiler_Design/lex_programs/abc.l
new file mode 100644
index 0000000..b1d057f
--- /dev/null
+++ b/Compiler_Design/lex_programs/abc.l
@@ -0,0 +1,16 @@
+%option noyywrap
+%{
+#include<string.h>
+%}
+
+%%
+abc {strcpy(yytext, "ABC"); ECHO;}
+. ECHO;
+%%
+
+int main(){
+	yyin = fopen("abc.txt", "r");
+	yyout = fopen("resul_abc.txt", "w");
+	yylex();
+	return 0;
+}
diff --git a/Compiler_Design/lex_programs/abc.txt b/Compiler_Design/lex_programs/abc.txt
new file mode 100644
index 0000000..3462879
--- /dev/null
+++ b/Compiler_Design/lex_programs/abc.txt
@@ -0,0 +1,3 @@
+sdjkagkdfjahsd abc
+\abc
+abc
diff --git a/Compiler_Design/lex_programs/vc.l b/Compiler_Design/lex_programs/vc.l
new file mode 100644
index 0000000..61db9d1
--- /dev/null
+++ b/Compiler_Design/lex_programs/vc.l
@@ -0,0 +1,16 @@
+%option noyywrap
+%{
+	int vowels=0, consonants=0;
+%}
+
+%%
+[aeiouAEIOU] vowels++;
+[a-zA-Z] consonants++;
+%%
+
+int main(){
+	yylex();
+	printf("\n\nvowels=%d \nconsonants=%d\n", vowels, consonants);
+	return 0;
+}
+
diff --git a/Compiler_Design/lex_programs/wcl.l b/Compiler_Design/lex_programs/wcl.l
new file mode 100644
index 0000000..db89278
--- /dev/null
+++ b/Compiler_Design/lex_programs/wcl.l
@@ -0,0 +1,17 @@
+%option noyywrap
+%{
+	int words=0, chars=0, lines=0;
+%}
+
+%%
+[a-zA-Z]+ {words++; chars+=yyleng;}
+\n {chars++; lines++;}
+. chars++;
+%%
+
+
+int main(){
+	yylex();
+	printf("\n\nwords=%d \ncharacters= %d \nlines= %d \n", words, chars, lines);	
+	return 0;
+}
diff --git a/Compiler_Design/yacc_programs/iden.l b/Compiler_Design/yacc_programs/iden.l
new file mode 100644
index 0000000..c968034
--- /dev/null
+++ b/Compiler_Design/yacc_programs/iden.l
@@ -0,0 +1,12 @@
+%option noyywrap
+%{
+#include "iden.tab.h"
+%}
+
+%%
+[0-9] { return DIGIT;}
+[_a-zA-Z] {return LETTER;}
+\n  {return NL;}
+.   {return yytext[0];}
+%%
+
diff --git a/Compiler_Design/yacc_programs/iden.y b/Compiler_Design/yacc_programs/iden.y
new file mode 100644
index 0000000..e577e9d
--- /dev/null
+++ b/Compiler_Design/yacc_programs/iden.y
@@ -0,0 +1,25 @@
+%{
+#include<stdio.h>
+#include<stdlib.h>
+%}
+
+%token NL DIGIT LETTER
+
+%%
+stmt: variable NL {printf("Valid Identifier\n"); return 0;}
+variable: LETTER alphanumeric
+alphanumeric: LETTER alphanumeric | DIGIT alphanumeric | LETTER | DIGIT
+
+%%
+int main()
+{
+    printf("Enter an Identifier\n");
+    yyparse();
+    return 0;
+}
+int yyerror()
+{
+  printf("Invalid Identifier!\n");
+  exit(0);
+}
+
diff --git a/Description.c b/Description.c
index aab0933..db78c07 100644
--- a/Description.c
+++ b/Description.c
@@ -1,13 +1,13 @@
-#include<stdio.h>
-#include<conio.h>
-void main()
-{
-  printf("WELCOME TO HACKTOBERFEST 2020!!!!!");
-  printf("So let's get started!");
-  printf("I guess everybody is a noobie here");
-  printf("My whole life was a bruh moment");
-  printf("\n What is life, anyway?");
-  printf("Hello there,this id Anushree VInod");
-  printf("My whole life was just great");
-  printf("With a little sunshine, we can make it through");
+#include <stdio.h>
+#include <conio.h>
+
+void main() {
+    printf("WELCOME TO HACKTOBERFEST 2020!!!!!");
+    printf("So let's get started!");
+    printf("I guess everybody is a noobie here");
+    printf("My whole life was a bruh moment");
+    printf("\n What is life, anyway?");
+    printf("Hello there,this id Anushree VInod");
+    printf("My whole life was just great");
+    printf("With a little sunshine, we can make it through");
 }
diff --git a/Factorial.c b/Factorial.c
new file mode 100644
index 0000000..07b09ea
--- /dev/null
+++ b/Factorial.c
@@ -0,0 +1,19 @@
+#include <stdio.h>
+int main() {
+    int n, i;
+    unsigned long long fact = 1;
+    printf("Enter an integer: ");
+    scanf("%d", &n);
+
+    // shows error if the user enters a negative integer
+    if (n < 0)
+        printf("Error! Factorial of a negative number doesn't exist.");
+    else {
+        for (i = 1; i <= n; ++i) {
+            fact *= i;
+        }
+        printf("Factorial of %d = %llu", n, fact);
+    }
+
+    return 0;
+}
diff --git a/Fibonacci.c b/Fibonacci.c
new file mode 100644
index 0000000..a41e7e3
--- /dev/null
+++ b/Fibonacci.c
@@ -0,0 +1,28 @@
+#include <stdio.h>
+int main() {
+
+  int i, n;
+
+  // initialize first and second terms
+  int t1 = 0, t2 = 1;
+
+  // initialize the next term (3rd term)
+  int nextTerm = t1 + t2;
+
+  // get no. of terms from user
+  printf("Enter the number of terms: ");
+  scanf("%d", &n);
+
+  // print the first two terms t1 and t2
+  printf("Fibonacci Series: %d, %d, ", t1, t2);
+
+  // print 3rd to nth terms
+  for (i = 3; i <= n; ++i) {
+    printf("%d, ", nextTerm);
+    t1 = t2;
+    t2 = nextTerm;
+    nextTerm = t1 + t2;
+  }
+
+  return 0;
+}
diff --git a/Leapyear.c b/Leapyear.c
new file mode 100644
index 0000000..5c9b310
--- /dev/null
+++ b/Leapyear.c
@@ -0,0 +1,27 @@
+#include <stdio.h>
+int main() {
+   int year;
+   printf("Enter a year: ");
+   scanf("%d", &year);
+
+   // leap year if perfectly divisible by 400
+   if (year % 400 == 0) {
+      printf("%d is a leap year.", year);
+   }
+   // not a leap year if divisible by 100
+   // but not divisible by 400
+   else if (year % 100 == 0) {
+      printf("%d is not a leap year.", year);
+   }
+   // leap year if not divisible by 100
+   // but divisible by 4
+   else if (year % 4 == 0) {
+      printf("%d is a leap year.", year);
+   }
+   // all other years are not leap years
+   else {
+      printf("%d is not a leap year.", year);
+   }
+
+   return 0;
+}
diff --git a/Primenumber.c b/Primenumber.c
new file mode 100644
index 0000000..9a38023
--- /dev/null
+++ b/Primenumber.c
@@ -0,0 +1,31 @@
+#include <stdio.h>
+
+int main() {
+
+  int n, i, flag = 0;
+  printf("Enter a positive integer: ");
+  scanf("%d", &n);
+
+  // 0 and 1 are not prime numbers
+  // change flag to 1 for non-prime number
+  if (n == 0 || n == 1)
+    flag = 1;
+
+  for (i = 2; i <= n / 2; ++i) {
+
+    // if n is divisible by i, then n is not prime
+    // change flag to 1 for non-prime number
+    if (n % i == 0) {
+      flag = 1;
+      break;
+    }
+  }
+
+  // flag is 0 for prime numbers
+  if (flag == 0)
+    printf("%d is a prime number.", n);
+  else
+    printf("%d is not a prime number.", n);
+
+  return 0;
+}
diff --git a/SCAN Disk Scheduling.c b/SCAN Disk Scheduling.c
index f64ff94..2923f80 100644
--- a/SCAN Disk Scheduling.c	
+++ b/SCAN Disk Scheduling.c	
@@ -1,7 +1,6 @@
 #include<stdio.h>
 #include<stdlib.h>
 
-
 void main(){
     int req_sq[10],i,j,n,head,seek_count=0,distance,rl[10],rg[10],irl=-1,irg=-1,temp;
     float avg;
@@ -18,30 +17,30 @@ void main(){
     for(i=0;i<n;i++){
         if(req_sq[i]<=head){
             rl[++irl]=req_sq[i];
-            
+
         }
         else{
-            rg[++irg]=req_sq[i];
-        }
+                rg[++irg]=req_sq[i];
+            }
     }
     for(i=0;i<irl;i++){
         for(j=i+1;j<irl+1;j++){
-                if(rl[j]>rl[i]){
-                    temp=rl[i];
-                    rl[i]=rl[j];
-                    rl[j]=temp;
-                }
-            
+            if(rl[j]>rl[i]){
+                temp=rl[i];
+                rl[i]=rl[j];
+                rl[j]=temp;
+            }
+
         }
     }
     for(i=0;i<irg;i++){
         for(j=i+1;j<irg+1;j++){
-                if(rg[j]<rg[i]){
-                    temp=rg[i];
-                    rg[i]=rg[j];
-                    rg[j]=temp;
-                }
-            
+            if(rg[j]<rg[i]){
+                temp=rg[i];
+                rg[i]=rg[j];
+                rg[j]=temp;
+            }
+
         }
     }
     for(i=0;i<=irl;i++){
@@ -56,7 +55,7 @@ void main(){
         seek_count+=distance;
         head=rg[i];
     }
-    avg=seek_count/n;
+    avg = seek_count/n;
     printf("\n\n  ============================================================\n\n");
     printf("  TOTAL SEEK TIME : %d",seek_count);
     printf("\n  AVERAGE SEEK TIME : %for",avg);
diff --git a/Two Pass_Asemble_Pass_2.c b/Two Pass_Asemble_Pass_2.c
new file mode 100644
index 0000000..db30c76
--- /dev/null
+++ b/Two Pass_Asemble_Pass_2.c	
@@ -0,0 +1,81 @@
+#include<stdio.h>
+#include<conio.h>
+#include<string.h>
+#include<ctype.h>
+#include<stdlib.h>
+int main()
+{
+FILE *fint,*ftab,*flen,*fsym,*fobj;
+int op1[10],txtlen,txtlen1,i,j=0,len;
+char add[5],symadd[5],op[5],start[10],temp[30],line[20],label[20],mne[10],operand[10],symtab[10],opmne[10];
+fint=fopen("intermediate.txt","r");
+flen=fopen("length.txt","r");
+ftab=fopen("optab.txt","r");
+fsym=fopen("symtab.txt","r");
+fobj=fopen("object_program.txt","w");
+fscanf(fint,"%s%s%s%s",add,label,mne,operand);
+if(strcmp(mne,"START")==0)
+{
+strcpy(start,operand);
+fscanf(flen,"%x",&len);
+}
+printf("H^%s^%s^%x\nT^00%s^15^",label,start,len,start);
+fprintf(fobj,"H^%s^%s^%x\nT^00%s^15^",label,start,len,start);
+fscanf(fint,"%s%s%s%s",add,label,mne,operand);
+while(strcmp(mne,"END")!=0)
+{
+fscanf(ftab,"%s%s",opmne,op);
+while(!feof(ftab))
+{
+if(strcmp(mne,opmne)==0)
+{
+fclose(ftab);
+fscanf(fsym,"%s%s",symadd,symtab);
+while(!feof(fsym))
+{
+if(strcmp(operand,symtab)==0)
+{
+printf("%s%s^",op,symadd);
+fprintf(fobj,"%s%s^",op,symadd);
+break;
+}
+else
+fscanf(fsym,"%s%s",symadd,symtab);
+}
+break;
+}
+else
+fscanf(ftab,"%s%s",opmne,op);
+}
+if((strcmp(mne,"BYTE")==0)||(strcmp(mne,"WORD")==0))
+{
+if(strcmp(mne,"WORD")==0)
+{
+    printf("00000%s^",operand);
+    fprintf(fobj,"00000%s^",operand);
+}
+else
+{
+len=strlen(operand);
+for(i=2;i<len;i++)
+{
+printf("%x",operand[i]);
+fprintf(fobj,"%x",operand[i]);
+}
+printf("^");
+fprintf(fobj,"^");
+}
+}
+fscanf(fint,"%s%s%s%s",add,label,mne,operand);
+ftab=fopen("optab.txt","r");
+fseek(ftab,SEEK_SET,0);
+}
+printf("\nE^00%s",start);
+fprintf(fobj,"\nE^00%s",start);
+fclose(fint);
+fclose(ftab);
+fclose(fsym);
+fclose(flen);
+getch();
+return 0;
+}
diff --git a/Two Pass_Assembler_Pass_1.c b/Two Pass_Assembler_Pass_1.c
new file mode 100644
index 0000000..1d7cdeb
--- /dev/null
+++ b/Two Pass_Assembler_Pass_1.c	
@@ -0,0 +1,87 @@
+#include<stdio.h>
+#include<string.h>
+#include<stdlib.h>
+void main()
+{
+FILE *f1,*f2,*f3,*f4, *f5, *f6;
+int lc,sa,l,op1,o,len;
+char m1[20],la[20],op[20],otp[20];
+
+f1=fopen("input.txt","r");
+f3=fopen("symtab.txt","w");
+f5=fopen("intermediate.txt", "w");
+f6=fopen("program.txt", "w");
+fscanf(f1,"%s %s %x",la,m1,&op1);
+if(strcmp(m1,"START")==0)
+{
+ sa=op1;
+ lc=sa;
+ printf("-\t%s\t%s\t%x\n",la,m1,op1);
+ fprintf(f5,"-\t%s\t%s\t%x\n",la,m1,op1);
+ }
+ else
+ lc=0;
+fscanf(f1,"%s %s",la,m1);
+while(!feof(f1))
+{
+ fscanf(f1,"%s",op);
+ if(strcmp(m1,"END")!=0)
+ {
+  fprintf(f5,"\n%x\t%s\t%s\t%s\n",lc,la,m1,op);
+  printf("\n%x\t%s\t%s\t%s\n",lc,la,m1,op);
+ }
+ else
+ {
+  fprintf(f5,"\n-\t%s\t%s\t%s\n",la,m1,op);
+  printf("\n-\t%s\t%s\t%s\n",la,m1,op);
+ }
+ if(strcmp(la,"-")!=0)
+ {
+ fprintf(f3,"\n%x\t%s\n",lc,la);
+ }
+ f2=fopen("optab.txt","r");
+ fscanf(f2,"%s %x",otp,&o);
+ while(!feof(f2))
+ {
+  if(strcmp(m1,otp)==0)
+  {
+    lc=lc+3;
+    break;
+  }
+  fscanf(f2,"%s %x",otp,&o);
+  }
+  fclose(f2);
+  if(strcmp(m1,"WORD")==0)
+ 
+    {
+   lc=lc+3;
+   }
+   else if(strcmp(m1,"RESW")==0)
+   {
+    op1=atoi(op);
+    lc=lc+(3*op1);
+    }
+    else if(strcmp(m1,"BYTE")==0)
+    {
+    if(op[0]=='X')
+      lc=lc+1;
+      else
+      {
+      len=strlen(op)-2;
+      lc=lc+len;}
+    }
+    else if(strcmp(m1,"RESB")==0)
+    {
+     op1=atoi(op);
+     lc=lc+op1;
+     }
+    fscanf(f1,"%s%s",la,m1);
+}
+    if(strcmp(m1,"END")==0)
+    {
+    printf("Program length = %x",lc-sa);
+    fprintf(f6, "%x", lc-sa);
+    }
+    fclose(f1);
+    fclose(f3);
+    }
diff --git a/branchless_compare_even_or_odd.c b/branchless_compare_even_or_odd.c
index c260dbe..bbfc4be 100644
--- a/branchless_compare_even_or_odd.c
+++ b/branchless_compare_even_or_odd.c
@@ -1,8 +1,9 @@
 #include <stdio.h>
-int main()
-{
+
+int main() {
     int i;
-    for(i = 0; i<10000; i++)
+
+    for (i = 0; i<10000; i++)
         /* print even or odd with branchless comparison */
-        (i%2==0)?printf("%d is %s\n",i,"Even"):printf("%d is %s\n",i,"Odd");
+        (i%2==0) ? printf("%d is %s\n", i, "Even") : printf("%d is %s\n", i, "Odd");
 }
diff --git a/cscan1.c b/cscan1.c
new file mode 100644
index 0000000..88d1fd5
--- /dev/null
+++ b/cscan1.c
@@ -0,0 +1,83 @@
+#include<stdio.h>
+void main()
+{
+    int trackpos[25],n,head,i,j,sum=0,maxrange,diff,temp,a[20],b[20],temp1=0,temp2=0;
+    float avg;
+    printf("Enter the maximum range of Disk : ");
+    scanf("%d",&maxrange);
+    printf("Enter the number of tracks : ");
+    scanf("%d",&n);
+    printf("Enter the initial position of header : ");
+    scanf("%d",&head);
+    printf("Enter the position of tracks : ");
+    for(i=0;i<n;i++)
+        {
+            scanf("%d",&temp);
+
+            if(temp>head)
+            {
+                a[temp1]=temp;
+                temp1++;
+            }
+            else
+                {
+                    b[temp2]=temp;
+                    temp2++;
+                }
+        }
+    for(i=0;i<temp1-1;i++)
+        {
+            for(j=i+1;j<temp1;j++)
+                {
+                    if(a[i]>a[j])
+                    {
+                        temp=a[i];
+                        a[i]=a[j];
+                        a[j]=temp;
+                    }
+                }
+        }
+    for(i=0;i<temp2-1;i++)
+        {
+            for(j=i+1;j<temp2;j++)
+                {
+                    if(b[i]>b[j])
+                    {
+                        temp=b[i];
+                        b[i]=b[j];
+                        b[j]=temp;
+                    }
+                }
+        }
+    for(i=1,j=0;j<temp1;i++,j++)
+        {
+            trackpos[i]=a[j];
+        }
+    trackpos[i]=maxrange;
+    trackpos[i+1]=0;
+    for(i=temp1+3,j=0;j<temp2;i++,j++)
+        {
+            trackpos[i]=b[j];
+        }
+
+    trackpos[0]=head;
+    printf("\nTrack position\tDifference between tracks");
+    for(i=0; i<=n+1; i++)
+        {
+            if(trackpos[i+1]>trackpos[i])
+            {
+                diff=trackpos[i+1]-trackpos[i];
+                sum=sum+diff;
+                printf("\n%d\t\t%d",trackpos[i+1],diff);
+            }
+            else
+                {
+                    diff=trackpos[i]-trackpos[i+1];
+                    sum=sum+diff;
+                    printf("\n%d\t\t%d",trackpos[i+1],diff);
+                }
+        }
+    avg=sum/(float)n;
+    printf("\nTotal movements of header : %d\n", sum);
+    printf("Average header movements : %f\n", avg);
+}
diff --git a/dvr.c b/dvr.c
index 048a62f..aef0888 100644
--- a/dvr.c
+++ b/dvr.c
@@ -1,38 +1,40 @@
-#include<stdio.h>
+#include <stdio.h>
 
-struct node{
+struct node {
 	unsigned dist[20];
 	unsigned from[20];
-}rt[10];
+} rt[10];
 
 int main(){
 	int dmat[20][20];
 	int n,i,j,k,count=0;
+
 	printf("\nEnter the number of nodes: ");
 	scanf("%d",&n);
 	printf("Enter the cost matrix: \n");
-	for(i=0;i<n;i++)
-		for(j=0;j<n;j++){
-			scanf("%d",&dmat[i][j]);
+
+	for(i=0; i<n; i++)
+		for(j=0; j<n; j++){
+			scanf("%d", &dmat[i][j]);
 			dmat[i][i] = 0;
 			rt[i].dist[j] = dmat[i][j];
 			rt[i].from[j] = j;
-		}
-		do{
+		} do {
 			count = 0;
-			for(i=0;i<n;i++)
-				for(j=0;j<n;j++)
-					for(k=0;k<n;k++)
-						if(rt[i].dist[j]>dmat[i][k]+rt[k].dist[j]){
-							rt[i].dist[j] = rt[i].dist[k]+rt[k].dist[j];
+			for(i=0; i<n; i++)
+				for(j=0; j<n; j++)
+					for(k=0; k<n; k++)
+						if(rt[i].dist[j] > dmat[i][k] + rt[k].dist[j]){
+							rt[i].dist[j] = rt[i].dist[k] + rt[k].dist[j];
 							rt[i].from[j] = k;
 							count++;
 						}
-		}while(count!=0);
-		for(i=0;i<n;i++){
+		} while(count != 0);
+
+		for (i=0; i<n; i++){
 			printf("\n\nState value for router %d is \n",i+1);
-			for(j=0;j<n;j++){
-				printf("\nNode %d via %d Distance %d",j+1,rt[i].from[j]+1,rt[i].dist[j]);
+			for(j=0; j<n; j++){
+				printf("\nNode %d via %d Distance %d", j+1, rt[i].from[j]+1, rt[i].dist[j]);
 			}
 		}
 		printf("\n");
diff --git a/fcfs.c b/fcfs.c
new file mode 100644
index 0000000..33b521d
--- /dev/null
+++ b/fcfs.c
@@ -0,0 +1,36 @@
+#include <stdio.h>
+
+void main() {
+    int i, j, n, head;
+    float avg, sum;
+    sum = 0;
+    int trackpos[20], stime[20];
+
+    printf("Enter number of tracks : ");
+    scanf("%d", &n);
+    printf("Enter position of header : ");
+    scanf("%d", &head);
+    printf("Enter position of tracks : ");
+
+    for(i=0; i<n; i++) {
+        scanf("%d", &trackpos[i]);
+        stime[i] = head - trackpos[i];
+
+        if(stime[i] < 0) {
+            stime[i] = trackpos[i]-head;
+        }
+        head = trackpos[i];
+        sum = sum + stime[i];
+    }
+
+    avg = sum/n;
+    printf("\nTrack position\tDifference between tracks");
+
+    for (i=0; i<n; i++) {
+        printf("\n%d\t\t%d", trackpos[i], stime[i]);
+    }
+
+    printf("\n\nTotal movements of header : %f ", sum);
+    printf("\nAverage of header movements : %f ", avg);
+    printf("\n");
+}
diff --git a/fib.c b/fib.c
index ded8156..c3e3358 100644
--- a/fib.c
+++ b/fib.c
@@ -1,17 +1,20 @@
-#include<stdio.h>  
-int main(){    
- int n,i,m=0,flag=0;    
- printf("Enter the number to check prime:");     
- scanf("%d",&n);    
- m=n/2;    
- for(i=2;i<=m;i++){    
-  if(n%i==0){    
-   printf("Number is not prime");    
-   flag=1;    
-   break;    
-  }    
- }    
- if(flag==0)    
- printf("Number is prime");     
- return 0;  
-}    
+#include <stdio.h>
+
+int main(){
+    int n, i, m = 0, flag=0;
+    printf("Enter the number to check prime:");
+    scanf("%d",&n);
+
+    m = n/2;
+    for(i=2; i<=m; i++){
+        if(n%i == 0){
+            printf("Number is not prime");
+            flag = 1;
+            break;
+        }
+    }
+    if(flag == 0)
+        printf("Number is prime");
+
+    return 0;
+}
diff --git a/fifo1.c b/fifo1.c
new file mode 100644
index 0000000..e74f169
--- /dev/null
+++ b/fifo1.c
@@ -0,0 +1,55 @@
+#include<stdio.h>
+
+void main() {
+    int i, j, pn, page[50], frame[10], fn, k, avail;
+    float pfault = 0, phit = 0, faultratio = 0, hitratio = 0;
+    printf("\nFIFO PAGE REPLACEMENT ALGORITHM\n");
+    printf("\n Enter the number of pages : ");
+    scanf("%d", & pn);
+    printf("\n Enter the page number : ");
+    for (i = 0; i < pn; i++) {
+        scanf("%d", & page[i]);
+    }
+    printf("\n Enter the number of frames : ");
+    scanf("%d", & fn);
+    for (i = 0; i < fn; i++) {
+        frame[i] = -1;
+    }
+    j = 0;
+    printf("\n\tReference string\t Page Frames\t\tHit or Fault\n");
+    for (i = 0; i < pn; i++) {
+        printf("\t\t%d\t\t", page[i]);
+        avail = 0;
+
+        for (k = 0; k < fn; k++) {
+            if (frame[k] == page[i]) {
+                phit++;
+                avail = 1;
+                for (k = 0; k < fn; k++) {
+                    printf("%d\t", frame[k]);
+                }
+                if (avail == 1) {
+                    printf(" H");
+                }
+            }
+        }
+        if (avail == 0) {
+            frame[j] = page[i];
+            j = (j + 1) % fn;
+            pfault++;
+            for (k = 0; k < fn; k++) {
+                printf("%d\t", frame[k]);
+            }
+            if (avail == 0) {
+                printf(" F");
+            }
+        }
+        printf("\n");
+    }
+    hitratio = phit / pn;
+    faultratio = pfault / pn;
+    printf("Page hit is %f\n", phit);
+    printf("Page Fault Is %f\n", pfault);
+    printf("Page hit ratio is %f\n ", hitratio);
+    printf("Page fault ratio is %f \n", faultratio);
+}
diff --git a/insert.c b/insert.c
new file mode 100644
index 0000000..3c2de07
--- /dev/null
+++ b/insert.c
@@ -0,0 +1,35 @@
+#include<stdio.h>
+int main(){
+
+   /* Here i & j for loop counters, temp for swapping,
+    * count for total number of elements, number[] to
+    * store the input numbers in array. You can increase
+    * or decrease the size of number array as per requirement
+    */
+   int i, j, count, temp, number[25];
+
+   printf("How many numbers u are going to enter?: ");
+   scanf("%d",&count);
+
+   printf("Enter %d elements: ", count);
+   // This loop would store the input numbers in array
+   for(i=0; i<count; i++)
+      scanf("%d", &number[i]);
+
+   // Implementation of insertion sort algorithm
+   for(i=1; i<count; i++){
+      temp = number[i];
+      j = i-1;
+      while((temp < number[j]) && (j >= 0)){
+         number[j+1] = number[j];
+         j = j-1;
+      }
+      number[j+1] = temp;
+   }
+
+   printf("Order of Sorted elements: ");
+   for(i=0; i<count; i++)
+      printf(" %d", number[i]);
+
+   return 0;
+}
diff --git a/look.c b/look.c
new file mode 100644
index 0000000..a3687d4
--- /dev/null
+++ b/look.c
@@ -0,0 +1,56 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(){
+    int RQ[100], i, j, n, TotalHeadMoment = 0, initial, size, move;
+    printf("Enter the number of Requests\n");
+    scanf("%d", &n);
+    printf("Enter the Requests sequence\n");
+    for (i = 0; i < n; i++)
+        scanf("%d", &RQ[i]);
+    printf("Enter initial head position\n");
+    scanf("%d", &initial);
+    printf("Enter total disk size\n");
+    scanf("%d", &size);
+    printf("Enter the head movement direction for high 1 and for low 0\n");
+    scanf("%d", &move);
+    for (i = 0; i < n; i++){
+        for (j = 0; j < n - i - 1; j++){
+            if (RQ[j] > RQ[j + 1]){
+                int temp;
+                temp = RQ[j];
+                RQ[j] = RQ[j + 1];
+                RQ[j + 1] = temp;
+            }
+        }
+    }
+    int index;
+    for (i = 0; i < n; i++){
+        if (initial < RQ[i]){
+            index = i;
+            break;
+        }
+    }
+    if (move == 1){
+        for (i = index; i < n; i++){
+            TotalHeadMoment = TotalHeadMoment + abs(RQ[i] - initial);
+            initial = RQ[i];
+        }
+        for (i = index - 1; i >= 0; i--){
+            TotalHeadMoment = TotalHeadMoment + abs(RQ[i] - initial);
+            initial = RQ[i];
+        }
+    }
+    else {
+        for (i = index - 1; i >= 0; i--){
+            TotalHeadMoment = TotalHeadMoment + abs(RQ[i] - initial);
+            initial = RQ[i];
+        }
+        for (i = index; i < n; i++){
+            TotalHeadMoment = TotalHeadMoment + abs(RQ[i] - initial);
+            initial = RQ[i];
+        }
+    }
+    printf("Total head movement is %d \n", TotalHeadMoment);
+    return 0;
+}
diff --git a/quick_sort.c b/quick_sort.c
index 96f5ec4..733c7d0 100644
--- a/quick_sort.c
+++ b/quick_sort.c
@@ -21,6 +21,7 @@ int main(){
 	
 	return EXIT_SUCCESS;
 }
+
 int partition(TYPE A[], int p, int r) {
 	TYPE x = A[r]; //pivot
 	int i = p - 1, j;
@@ -34,6 +35,7 @@ int partition(TYPE A[], int p, int r) {
 	swap(TYPE, A[i], A[r]);
 	return i;
 }
+
 void quick_sort(TYPE A[], int p, int r) {
 	if(p < r) {
 		int t = (rand() % ( r - p + 1) + p);
@@ -45,6 +47,7 @@ void quick_sort(TYPE A[], int p, int r) {
 		quick_sort(A, q + 1, r);
 	}
 }
+
 void print_array(TYPE A[], int n) {
 	int i = 0;
 	putchar('[');
@@ -53,4 +56,4 @@ void print_array(TYPE A[], int n) {
 		printf("%d", A[i++]); 
 	}
 	puts("]");
-}
\ No newline at end of file
+}
diff --git a/scan.c b/scan.c
new file mode 100644
index 0000000..718781c
--- /dev/null
+++ b/scan.c
@@ -0,0 +1,83 @@
+#include<stdio.h>
+void main()
+{
+int trackpos[25],n,head,i,j,sum=0,
+maxrange,diff,temp,a[20],b[20],temp1=0,temp2=0;
+float avg;
+printf("Enter the maximum range of Disk: ");
+scanf("%d",&maxrange);
+printf("Enter the number of tracks : ");
+scanf("%d",&n);
+printf("Enter the initial position of header : ");
+scanf("%d",&head);
+printf("Enter the position of tracks : ");
+for(i=0;i<n;i++)
+{
+scanf("%d",&temp);
+if(temp>head)
+{
+a[temp1]=temp;
+temp1++;
+}
+else
+{
+b[temp2]=temp;
+temp2++;
+}
+}
+for(i=0;i<temp1-1;i++)
+{
+for(j=i+1;j<temp1;j++)
+{
+if(a[i]>a[j])
+{
+temp=a[i];
+a[i]=a[j];
+a[j]=temp;
+}
+}
+}
+for(i=0;i<temp2-1;i++)
+{
+for(j=i+1;j<temp2;j++)
+{
+
+if(b[i]<b[j])
+{
+temp=b[i];
+b[i]=b[j];
+b[j]=temp;
+}
+}
+}
+for(i=1,j=0;j<temp1;i++,j++)
+{
+trackpos[i]=a[j];
+}
+trackpos[i]=maxrange;
+for(i=temp1+2,j=0;j<temp2;i++,j++)
+{
+trackpos[i]=b[j];
+}
+trackpos[i]=0;
+trackpos[0]=head;
+printf("\nTrack position\tDifference between tracks\n");
+for(i=0; i<=n; i++)
+{
+if(trackpos[i+1]>trackpos[i])
+{
+diff = trackpos[i+1]-trackpos[i];
+sum = sum + diff;
+printf("%d\t\t%d\n",trackpos[i+1], diff);
+}
+else
+{
+diff=trackpos[i]-trackpos[i+1];
+sum=sum+diff;
+printf("%d\t\t%d\n",trackpos[i+1],diff);
+}
+}
+avg = sum/(float)n;
+printf("Total movement of head : %d\n", sum);
+printf("Average head movement : %f\n", avg);
+}
diff --git a/search.c b/search.c
index df676d7..b60d63c 100644
--- a/search.c
+++ b/search.c
@@ -1,6 +1,6 @@
 #include <stdio.h> 
-int binarySearch(int ar[], int l, int r, int x) 
-{ 
+
+int binarySearch(int ar[], int l, int r, int x) { 
     if (r >= l) { 
         int mid = l + (r - l) / 2; 
         if (ar[mid] == x) 
@@ -12,8 +12,7 @@ int binarySearch(int ar[], int l, int r, int x)
     return -1; 
 } 
   
-int main(void) 
-{ 
+int main(void) { 
     int ar[] = { 2, 3, 4, 10, 40 }; 
     int n = sizeof(ar) / sizeof(ar[0]); 
     int x = 10; 
diff --git a/select.c b/select.c
new file mode 100644
index 0000000..4a56e77
--- /dev/null
+++ b/select.c
@@ -0,0 +1,34 @@
+#include <stdio.h>
+
+int main() {
+    int array[100], n, c, d, position, t;
+
+    printf("Enter number of elements\n");
+    scanf("%d", &n);
+
+    printf("Enter %d integers\n", n);
+
+    for (c = 0; c < n; c++)
+        scanf("%d", &array[c]);
+
+    for (c = 0; c < (n - 1); c++) {
+        position = c;
+
+        for (d = c + 1; d < n; d++) {
+            if (array[position] > array[d])
+                position = d;
+        }
+        if (position != c) {
+            t = array[c];
+            array[c] = array[position];
+            array[position] = t;
+        }
+    }
+
+    printf("Sorted list in ascending order:\n");
+
+    for (c = 0; c < n; c++)
+        printf("%d\n", array[c]);
+
+    return 0;
+}
diff --git a/sjf.c b/sjf.c
index e01e064..00f0aea 100644
--- a/sjf.c
+++ b/sjf.c
@@ -90,8 +90,7 @@ void resulttime(int process[],int n,int process_burst[],int process_arrival[])
 
  /* Driver Code */
 
-void main()
-{
+void main() {
 	int n;
 	printf("\nEnter number of processes:");
 	scanf("%d",&n);
diff --git a/sstf.c b/sstf.c
new file mode 100644
index 0000000..b29167e
--- /dev/null
+++ b/sstf.c
@@ -0,0 +1,35 @@
+#include<stdio.h>
+#include<stdlib.h>
+int main()
+{
+    int r[100],i,n,TotalHeadMoment=0,initial,count=0;
+    printf("Enter the number of Requests\n");
+    scanf("%d",&n);
+    printf("Enter the Requests sequence\n");
+    for(i=0;i<n;i++)
+     scanf("%d",&r[i]);
+    printf("Enter initial head position\n");
+    scanf("%d",&initial);
+    
+    while(count!=n)
+    {
+        int min=1000,d,index;
+        for(i=0;i<n;i++)
+        {
+           d=abs(r[i]-initial);
+           if(min>d)
+           {
+               min=d;
+               index=i;
+           }
+           
+        }
+        TotalHeadMoment=TotalHeadMoment+min;
+        initial=r[index];
+        r[index]=1000;
+        count++;
+    }
+    
+    printf("Total head movement is %d",TotalHeadMoment);
+    return 0;
+}
diff --git a/validParenthesis.py b/validParenthesis.py
new file mode 100644
index 0000000..0842a18
--- /dev/null
+++ b/validParenthesis.py
@@ -0,0 +1,15 @@
+class Solution:
+    def isValid(self, s: str) -> bool:
+        Map = {")": "(", "]": "[", "}": "{"}
+        stack = []
+
+        for c in s:
+            if c not in Map:
+                stack.append(c)
+                continue
+            if not stack or stack[-1] != Map[c]:
+                return False
+            stack.pop()
+
+        return not stack
+