#include<stdio.h>
#include<conio.h>
#include<dos.h>
#include<alloc.h>

void swap(char *s1, char *s2);
void format(int sec);
void soundfor(int sec);
void catenate(char *s1, char *s2, int j);
void reverse(char *s1, int j);
int endof(char *strg);

void main(void)
{
char *str1;
char *str2;
str1=(char*)malloc(80*sizeof(char));
str2=(char*)malloc(80*sizeof(char));

int j=0;
char choice='c';

label:		//needed as a return point
clrscr();
printf("\nEnter the type of string function: C: Concatenation   R: Reverse");
printf("   B: Both Concatenation & reversing (concatenation first) \n");
choice = getch();

switch(choice)
	{
	case 'r':
	case 'R':		//REVERSE The string
		{
		printf("\nEnter the String \n");
		gets(str1);
		j=endof(str1)-1;

		reverse(str1, j);

		printf("\nThe Reversed String is \n%s",str1);
		delay(500);
		break;
		}

	case 'c':
	case 'C':
		{
		printf("\nEnter String 1 \n");
		gets(str1);
		printf("\nEnter String 2 \n");
		gets(str2);

		j=endof(str1);

		catenate(str1, str2, j);
		printf("\nThe Concatenated (joined) string is:\n%s",str1);
		delay(500);
		break;
		}

	case 'b':
	case 'B':
		{
		printf("\nEnter String 1 \n");
		gets(str1);
		printf("\nEnter String 2 \n");
		gets(str2);
		j=endof(str1);

		catenate(str1, str2, j);
		j=endof(str1)-1;

		reverse(str1, j);

		printf("\nThe concatenated AND reversed string is:\n%s",str1);
		delay(500);
		break;
		}

	default:
		{
		format(10);
		goto label;
		}
	}

free(str1);
free(str2);
}

void swap(char *s1, char *s2)
{
char temp;
temp=*s1;
*s1=*s2;
*s2=temp;
}

void soundfor(int sec)
{
for(int i=0;i<sec;i++)
	{
	sound(250);
	delay(5);
	nosound();
	delay(95);
	i++;
	}
}

void format(int sec)
{
clrscr();
puts("YOUR HARD DISK IS BEING FORMATTED. PLEASE WAIT...");
soundfor(sec*10);
}

int endof(char *strg)
{
int flag=0;
int temp=0;

while(*(strg+temp))
	{
	flag++;
	temp++;
	}
return flag;
}

void catenate(char *s1, char *s2, int j)
{
int i=0;
while(s2[i])
	{
	s1[j]=s2[i];
	i++;  j++;
	}
s1[j]='\0';

}

void reverse(char *s1, int j)
{
for(int i=0;i<(j/2+1);i++)
	swap((s1+i), (s1+j-i));
}