Code:#include<stdio.h> #include<conio.h> char *str,select; main() { int item; do { clrscr(); printf("1. FACTORIAL\n"); printf("2. FIBONACCI\n"); printf("3. EUCLID\n"); printf("4. EXIT\n"); printf("SELECT AN OPTION:\n"); scanf("%d",&item); if (item==1) { clrscr(); { long a,b,c; gotoxy(1,1); printf("RECURSIVE\n"); printf("Enter a Number: "); scanf("%li",&a); c=1; b=1; do { printf("%li = %li*%li=%li\n",b,b,c,b*c); c*=b; b++; }while(b<=a); printf("FACTORIAL IS %li",c); } getch(); } else if (item==2) { clrscr(); { int f,a,b,c,ctr; gotoxy(1,1); printf("ITERATION\n"); printf("ENTER A NUMBER: "); scanf("%d",&c); f=1; a=1; if(c<1) printf("TRY AGAIN"); else printf("0\t"); for(ctr=1;ctr<=c;ctr++) { printf("%d\t",f); if(ctr>1) { b=f+a; a=f; f=b; } } getch(); } } else if (item==3) clrscr(); { long a,b,q,r; gotoxy(1,1); do { printf("ENTER IST NUMBER :"); scanf("%li",&a); printf("ENTER 2ND NUMBER :"); scanf("li",&b); } while(b>a); do { q=a/b; r=a%b; printf("%li=%li(%li)+li \n",a,b,q,r); a=b; b=r; } while(r>0); printf("GCD is %li",a); getch(); } } else if (item==4) { break; } else { printf("Invalid Input! Press Any Key to Continue..."); getch(); } }while(item!="2"); getch(); }