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`putchar'--write a character (macro)

     #include <stdio.h>
     int putchar(int CH);
     int _putchar_r(void *REENT, int CH);
`putchar' is a macro, defined in `stdio.h'.  `putchar' writes its
argument to the standard output stream, after converting it from an
`int' to an `unsigned char'.
   The alternate function `_putchar_r' is a reentrant version.  The
extra argument REENT is a pointer to a reentrancy structure.
If successful, `putchar' returns its argument CH.  If an error
intervenes, the result is `EOF'.  You can use ``ferror(stdin)'' to
query for errors.
ANSI C requires `putchar'; it suggests, but does not require, that
`putchar' be implemented as a macro.
   Supporting OS subroutines required: `close', `fstat', `isatty',
`lseek', `read', `sbrk', `write'.