File I/O Functions

(open <fname> &key :direction)  OPEN A FILE STREAM
    <fname>     the file name string or symbol
    :direction  :input or :output (default is :input)
    returns     a stream

(close <stream>)  CLOSE A FILE STREAM
    <stream>    the stream
    returns     nil

(read-char [<stream>])  READ A CHARACTER FROM A STREAM
    <stream>    the input stream (default is standard input)
    returns     the character

(peek-char [<flag> [<stream>]])  PEEK AT THE NEXT CHARACTER
    <flag>      flag for skipping white space (default is nil)
    <stream>    the input stream (default is standard input)
    returns     the character (integer)

(write-char <ch> [<stream>])  WRITE A CHARACTER TO A STREAM
    <ch>        the character to write
    <stream>    the output stream (default is standard output)
    returns     the character

(read-line [<stream>])  READ A LINE FROM A STREAM
    <stream>    the input stream (default is standard input)
    returns     the string

(read-byte [<stream>])  READ A BYTE FROM A STREAM
    <stream>    the input stream (default is standard input)
    returns     the byte (integer)

(write-byte <byte> [<stream>])  WRITE A BYTE TO A STREAM
    <byte>      the byte to write (integer)
    <stream>    the output stream (default is standard output)
    returns     the byte (integer)