In C, return type of getchar(), fgetc() and getc() is int (not char). So it is recommended to assign the returned values of these functions to an integer type variable. 

  char ch;  /* May cause problems */
  while ((ch = getchar()) != EOF)
  {
     putchar(ch);
  }

Here is a version that uses integer to compare the value of getchar().

  int in;
  while ((in = getchar()) != EOF)
  {
     putchar(in);
  }

See this for more details.

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