Editing Parallel port (section)

=== Program interface ===
In versions of [[Microsoft Windows|Windows]] that did not use the [[Windows NT]] kernel (as well as [[DOS]] and some other operating systems), programs could access the parallel port with simple outportb() and inportb() subroutine commands. In operating systems such as [[Windows NT]] and [[Unix]] ([[NetBSD]], [[FreeBSD]], [[Solaris (operating system)|Solaris]], [[386BSD]], etc.), the microprocessor is operated in a different security ring, and access to the parallel port is prohibited, unless using the required driver. This improves security and arbitration of device contention. On Linux, inb() and outb() can be used when a process is run as root and an ioperm() command is used to allow access to its [[base address]]; alternatively, ppdev allows shared access and can be used from userspace if the appropriate permissions are set.

The cross-platform library for parallel port access, libieee1284, also is available on many Linux distributions and provides an abstract interface to the parallel ports of the system. Access is handled in an open-claim-release-close sequence, which allows for concurrent access in userspace.