Thread: basic doubt in pointer concept

>void main()
void main is wrong, main must return an int and nothing else or the program is undefined. The correct definition of main is

int main ( void )

You must also return a value at the end of main, 0 is a portable value for successful termination.

>str[i] = malloc(10);
You use malloc yet I don't see stdlib.h included anywhere, this is undefined behavior and is the cause of your warning. Since malloc is not defined, the compiler assumes it is a function that returns int, yet you assign the return value to a pointer. Include stdlib.h and the problem will be fixed.

>scanf("%s",str[i]) ;
scanf is really unsafe when used like this because there is no way to be sure that you aren't reading more than 10 characters. Buffer overflow is a very real problem. I recommend fgets for reading string data.

>printf(" the name of the first students is %s\n",*(str+0));
This is okay for practice programs, but pointer notation should be avoided when possible because array notation is simpler and easier to understand at a glance:

printf ( " the name of the first students is %s\n", str[0] );

Code:

#include <stdio.h>
#include <stdlib.h>

int main ( void )
{
 char *str[3] = {0}; /* NULL the three pointers */
 int i;

  for ( i = 0; i < 3; i++ ) {
    printf ( "Enter the name of a student: " );

    if ( ( str[i] = malloc ( 10 ) ) == NULL ) {
      printf ( "Error allocating memory\n" );

      /*
      ** Don't do this, free the memory you've allocated
      ** before terminating the program.
      */
      exit ( EXIT_FAILURE );
    }

    fgets ( str[i], 10, stdin );
  }

  printf ( "The name of the first student is %s\n", str[0] );
  printf ( "The name of the second student is %s\n", str[1] );
  printf ( "The name of the third student is %s\n", str[2] );

  free ( str[0] );
  free ( str[1] );
  free ( str[2] );

  printf ( "Hit return to exit" );
  getchar();

  return EXIT_SUCCESS; /* EXIT_SUCCESS is defined in stdlib.h */
}

-Prelude