Input and Output

(maybe-read-charport) procedure
$\Longrightarrow$ character or false

maybe-read-char when invoked on a port will return the next character if one is available; otherwise, it will return immediately with a value of false.

(char-ready?port) procedure
$\Longrightarrow$ boolean

char-ready? returns true if a character is available for input; otherwise, it returns false.