The READIO function returns the contents of a hardware register of an interface. The value of the first argument specifies an interface select code and a valid interface register number is specified as the second argument. That hardware interface register is read and its contents are returned. For example:
PRINT "Register=";READIO(7,1)
This prints the contents of interface register number 1on interface number 7.
Extensions to READIO and WRITEIO allow PEEK and POKE operations. Other extensions allow the address of a numeric variable to be read, and assembly language subroutines to be called. All these extensions are explained later in this section.
