Unix system calls for tape interfaces.

Most of the tapes in Unix are controlled basically in the same way:

• The interface between the program and the tape driver program is the same as for normal files, when using system calls like open(), close(), read() and write().
• For special tape commands like rewind, skip back a file etc... a different interface is used. The system call is standard Unix and is called ioctl(). It accepts as parameter the tape command to be executed and can return a status of the tape. The differences between one machine and another are the names and number of commands supported by the device (usually defined in an system include file called mtio.h), and the status codes (usually undefined).