C Program Takes Alphabetic Phones Numbers and Converts into Numberic Form - c

Question

I'm working on a C code that will take an alphabetic phone number and convert into numbers. I'm stuck on the output. The output wil drop numbers needed. Such as 1-800-GATOR, will return 42867 but not 1-800-42867. This is what I have so far....
#include <ctype.h>
#include <stdio.h>
int main (void)
{
char ch;
int num_vowels = 0;
printf("Please Enter a phone number: ");
while ((ch = getchar()) != '\n')
{
switch (ch) {
case 'A': case 'B': case 'C':
putchar('2');
break;
}
switch (ch) {
case 'D': case 'E': case 'F':
putchar ('3');
break;
}
switch (ch) {
case 'G': case 'H': case 'I':
putchar ('4');
break;
}
switch (ch) {
case 'J': case 'K': case 'L':
putchar ('5');
break;
}
switch (ch) {
case 'M': case 'N': case 'O':
putchar ('6');
break;
}
switch (ch) {
case 'P': case 'Q': case 'R': case 'S':
putchar ('7');
break;
}
switch (ch) {
case 'T': case 'U': case 'V':
putchar ('8');
break;
}
switch (ch) {
case 'W': case 'X': case 'Y': case 'Z':
putchar ('9');
break;
}
printf("%c", num_vowels);
}
return 0;
}
Is it something that I'm missing in printf("%c", num_vowels);?
Any help is appricated!

Answer 1

You may have misunderstood the switch statement. While your usage does perform correctly, you only need one statement with multiple cases:
switch (ch) {
case 'A': case 'B': case 'C':
putchar('2');
break;
case 'D': case 'E': case 'F':
putchar('3');
break;
case 'G': case 'H': case 'I':
putchar('4');
break;
/* ... */
}
Note that nothing happens when the input doesn't match any of the cases. That's why only capital letters are transformed and sent to the output. One simple solution would be adding a default case. This way, when the input character is not any capital letter it is sent straight to output. Add this to the end of your switch:
switch(ch) {
case 'A': case 'B':
/* ... */
default:
putchar(ch);
break;
}
You could perform other checks as well, only printing certain characters for example.
As for printf("%c", num_vowels); there is nothing wrong with it, except that num_vowels is never used. So you should expect it to print a null character ('\0') after every character sent to output. I'm not sure about your intentions, but if it was a counter, you should increment the variable and print it only after reading input, outside the while loop.
#include <stdio.h>
#include <ctype.h>
int
main(int argc, char **argv)
{
char ch;
int num_letters = 0;
printf("Please Enter a phone number: ");
while ((ch = getchar()) != '\n')
{
if (isupper(ch)) num_letters++;
switch (ch) {
case 'A': case 'B': case 'C':
putchar('2');
break;
case 'D': case 'E': case 'F':
putchar('3');
break;
case 'G': case 'H': case 'I':
putchar('4');
break;
case 'J': case 'K': case 'L':
putchar('5');
break;
case 'M': case 'N': case 'O':
putchar('6');
break;
case 'P': case 'Q': case 'R': case 'S':
putchar('7');
break;
case 'T': case 'U': case 'V':
putchar('8');
break;
case 'W': case 'X': case 'Y': case 'Z':
putchar('9');
break;
default:
putchar(ch);
break;
}
}
printf("\n-- %d alphabetic letters used.\n", num_letters);
return 0;
}

Answer 2

Use int ch instead of char ch because getchar returns int. You should compare ch with EOF and handle that case.
Your code doesn't handle the case where a user enters a lower-case letter (e.g. 'a' instead of 'A'). You can correct this by using ch = toupper(ch);
You don't need to repeat each switch() statement.
num_vowels isn't being modified.
printf("%c", num_vowels) should be printf("%d") as num_vowels represents a human-readable number, not a character value.
printf(... should be after your while loop, not inside it.
You cannot use getchar and putchar to supplant user-input (i.e. disable local input echo), that requires platform-specific APIs. I recommend prompting the user to input a whole line of text first (into a char*), then process the line of text.

Answer 3

I guess you are wrong with how you are processing the input.
When you are taking input from the user i.e. 1-800-GATOR, you should skip the first 6 characters i.e "1-800-" and then start your switch case loop.
Also, the variable num_vowels is unchanged since you defined it till you print it. Why are you using it?
The code that will work for your statement will be:
#include <stdio.h>
int main (void)
{
char ch;
//int num_vowels = 0;
printf("Please Enter a phone number: ");
while ((ch = getchar()) != '\n')
{
switch (ch) {
case 'A': case 'B': case 'C':
putchar('2');
break;
case 'D': case 'E': case 'F':
putchar ('3');
break;
case 'G': case 'H': case 'I':
putchar ('4');
break;
case 'J': case 'K': case 'L':
putchar ('5');
break;
case 'M': case 'N': case 'O':
putchar ('6');
break;
case 'P': case 'Q': case 'R': case 'S':
putchar ('7');
break;
case 'T': case 'U': case 'V':
putchar ('8');
break;
case 'W': case 'X': case 'Y': case 'Z':
putchar ('9');
break;
}
}
printf("\n");
return 0;
}