Newbie - tolower()

I'm having problems with using the "tolower".

I made a very small program to test:

Code:

#include <stdio.h>
#include <ctype.h>
int main()
{

char ch;

printf("Enter A Letter\n");
scanf("%c", ch);
ch = tolower(ch);
printf("%c", ch);
return 0;
}

This is what happens when I run the program:
The last line is the error. What am I doing wrong!?

Enter A Letter
G
Segmentation fault

Use
scanf("%c", &ch);
But because tolower and toupper functions take and return int, I suggest you to use

Code:

int ch;
...
ch = getchar();
ch = tolower(ch);
...

Actually that's not it at all. The real problem is that your scanf call is wrong:

Code:

#include <stdio.h>
#include <ctype.h>
int main()
{

char ch;

printf("Enter A Letter\n");
scanf("%c", ch);
ch = tolower(ch);
printf("%c", ch);
return 0;
}

You forgot the address-of operator:

Code:

#include <stdio.h>
#include <ctype.h>
int main()
{

    char ch;

    printf("Enter A Letter\n");
    scanf("%c", &ch );
    ch = tolower(ch);
    printf("%c", ch);
    return 0;
}

Quzah.

Originally Posted by quzah

Actually that's not it at all

Really?
What about second line in my post?

What about second line in my post?

I think he was talking about 98dodgeneondohc's post, not yours

ok thanks for the help people! I'm just trying to teach myself programming. I always thought the "&" was only to be used with integers. What is the "&" for and why is it needed?

Another thing... if I was to enter in a sentence, and I make an array for example: char sentence[50];

Upon running the program, I enter in the sentence seperated by a spacebar, it would only show the first word! How do I make it so it takes the whole sentence?

ok '&' is the one which give u the address, think of something like this

Code:

int i;

when u say                                                                                                          _________
&i --> it gives you the address of 'i' i.e  where the 'i' is located in the memory  |                 |
                                                                                                                            ---------------
                                                                                                                1000            i

so when u say &i -->  it gives you the address of 'i ' in this case it is 1000

scanf the syantx is as follow

Code:

scanf("const char format", ... varibale);

scanf function always requires address of the variable in order to place the value entered by the user. u are expected to specilfy '&' in front of the variable. in your case

Code:

scanf("%c", ch);

the scanf is expecting the address of the variable ch to place u'r char eneted in the memory

>Upon running the program, I enter in the sentence seperated by a spacebar, it would only show the first word! How do I make it so it takes the whole sentence?
that is b'cose the scanf() fucntion reads the string up to the white space the rest is lost.

the better way of doing this is to use fgets function to read the string. and this syntax is as follow
[code]
fgets(char *, int, FILE *);
[code]

example:

Code:

#include<stdio.h>

int main()
{
        char str[20];
        
       fgets(str, sizeof str, stdin);  // read the string
       printf("%s",str);       //  print the string on to the  screen

       getchar();
}

/* output: -
hello world
hello world
*/

hope this helps

s.s.harish

good explanation! thanks!