Am I using pointers correctly here?

I have a simple program I am coding for my class and so far I have got the program to do what I want it to do, however I am not sure if I am using pointers as my professor had asked us to use in this program correctly.

Could someone take a look at this code and let me know if I am actually using pointers here to convert a line of text to uppercase and then lowercase?

Code:

#include <stdio.h>
#include <ctype.h>

main()
{
	/* Variable declarations */
	char text[26];
	int i;
	char *text_Ptr = text;
	
	/* Prompt user for line of text */
	printf ("\nEnter a line of text (up to 25 characters):\n");
	gets(text);
	
	/* Convert and output the text in uppercase characters */
	printf ("\nThe line of text in uppercase is:\n");
	
	i = 0;
	while ( text[i] != '\0')
	{
		putchar( toupper(text_Ptr[i++]) ); <--- should the text_Ptr have a * here?
	}
	
	/* Convert and output the text in lowercase characters */
	printf ("\n\nThe line of text in lowercase is:\n");
	
	i = 0;
	while ( text[i] != '\0')
	{
		putchar( tolower(text_Ptr[i++]) ); <--- should the text_Ptr have a * here?
	}
	
	printf ("\n");
	
} /* end main */

I seem to believe that I am suppose to have an * next to text_Ptr throughout the code, however when I put the * the code does not compile correctly and gives this error "invalid type argument of `unary *'".

Any help is much appreciated.

Originally Posted by kisiellll

I seem to believe that I am suppose to have an * next to text_Ptr throughout the code, however when I put the * the code does not compile correctly and gives this error "invalid type argument of `unary *'".

No, the compiler is right and you are wrong (in your conviction, not your code).

Ie. there SHOULD NOT be an asterisk there, that would be dereferencing the pointer. The asterisk is "over-loaded" in C (it can have more than one meaning, depending on context).

The index operator [] also dereferences the pointer, so you are fine.
However, the code is not fine. You should take a look at these:
- Gets - why it's bad and why you should avoid it.
- Implicit main - why it's frowned over and why you should avoid it.

Yeah I know about using gets and my style of using main, but its what my professor wants us to use for some reason. Its an introductory course so I think hes just trying to keep it simple for now, although I feel it could create bad habits.

Anyways I revised my code and I think I'm doing the entire process correctly using pointers as my professor had assigned.

Heres the new code:

Code:

#include <stdio.h>
#include <ctype.h>

main()
{
	/* Variable declarations */
	char text[26];
	char *textPtr;
	
	/* Prompt user for line of text */
	printf ("\nEnter a line of text (up to 25 characters):\n");
	gets(text);
	
	textPtr = text; /* point textPtr to text */
	
	/* Convert and output the text in uppercase characters */
	printf ("\nThe line of text in uppercase is:\n");
	
	/* Loop to convert to uppercase */
	while ( *textPtr )
	{
		*textPtr = toupper(*textPtr);
		textPtr++;
	} /* end while */
	
	/* Output uppercase line of text */
	printf("%s\n", text);
	
	textPtr = text; /* Convert textPtr back to original text */
	
	/* Convert and output the text in lowercase characters */
	printf ("\nThe line of text in lowercase is:\n");
	
	/* Loop to convert to lowercase */
	while ( *textPtr )
	{
		*textPtr = tolower(*textPtr);
		textPtr++;
	} /* end while */
	
	/* Output lowercase line of text */
	printf("%s\n", text);
	
} /* end main */

Another bad teacher... does your teacher care if you use proper code, though?
If your professor does, remember to slam the course after you're done with it.