/*

* rep_alpha.c

* This program reads a string and replaces all the alphabetic characters

* in it, according to a given replacement table.

*/

#include <stdio.h>

#include <ctype.h>

#define MAX_LEN 200

int main ()

{

char rep_tab[] = "QWERTYUIOPASDFGHJKLZXCVBNM";

/* The replacement table: The i'th character

* in the Latin alphabet should be replaced

* by the i'th character of this string. */

char str_in [MAX_LEN + 1]; /* The input string. */

int l_str; /* Its length. */

char str_out [MAX_LEN + 1]; /* The output string. */

int c;

int i;

/* Read the input string, character by character. */

printf ("Please enter the input string: ");

l_str = 0;

c = getchar();

while (c != '\n' && c != EOF)

{

/* Watch out for inputs that are too long! */

if (l_str > MAX_LEN)

{

printf ("Error -- input string too long.\n");

return (1);

}

/* Store the current character. */

str_in[l_str] = c;

l_str++;

/* Read the next input character. */

c = getchar();

}

/* Take care of the terminating NULL. */

str_in[l_str] = '\0';

/* Go over the input characters. */

for (i = 0; i < l_str; i++)

{

/* Check if the current character is a letter. */

if (isalpha (str_in[i]))

{

/* Convert to an upper-case character and use the replacement table to

* obtain the target character. */

c = toupper (str_in[i]);

str_out[i] = rep_tab[c - 'A'];

}

else

{

/* Not a letter: Leave the character as is. */

str_out[i] = str_in[i];

}

}

/* Take care of the terminating NULL. */

str_out[l_str] = '\0';

/* Print the two string. */

printf ("Input : %s\n", str_in);

printf ("Output: %s\n", str_out);

return (0);

}