[plt-scheme] Writing Bytes into a file

are there any fonctions like these , to write bytes into a file , with plt
scheme ?

(write-byte byte binary-output-port) ; writes an exact 8-bit integer and
returns an unspecified value
(read-byte binary-input-port)  ; returns an exact integer, or an end-of-file
object

(I found these functions here :
http://www.cs.hmc.edu/~fleck/envision/user-manual/binary-files.html )