Code:int main () { char str1[100]; char str2[100]; int d=1; int ch; int choose; printf("Enter the first string : \n"); gets (str1); printf("Enter the second string : "); gets (str2); while(d==1){ printf(" Enter one to remove duplicates from the first string\n" " Enter two to concatenate the two strings\n" " Enter three to sort strings\n" " Enter four to Separate str1 into tokens\n"); scanf("%d",&choose); if (choose==1) { remove_duplicates (str1);} if(choose==2){ printf("the two string after concatenate %s\n",strcon(str1,str2));} if (choose==3){ sort_string(str1); sort_string(str2); printf("%s\n",str1); printf("%s\n",str2); } if (choose==4){ printf("the str1 after Separate it into tokens is \n"); sentancetoken(str1); } printf("do you want to do another operation Enter 1 for yes and 2 for no\n "); scanf("%d",&d); printf("do you want to change the strings Enter 1 for yes and 2 for no"); scanf("%d",ch); if(ch==1){ printf("Enter the New first string : \n"); gets (str1); printf("Enter the New second string : "); gets (str2);} } getch (); return 0;