What is return type of getchar(), fgetc() and getc() ?

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.