A General Purpose Magnetic Tape Handler EXTMT is a FORTRAN callable magnetic tape handler written in RT-11 MACRO. It is capable of reading or writing tapes in any arbitrary format. As herein implemented, the tape is mount- ed on drive zero. Use the "SET" keyboard command to select tape density and/or lateral parity. To change the unit number, it is necessary to change the contitional assembly switch "CHANGE" in the assignments section of the MACRO source as desired prior to assembly of the subroutine. Complete instructions on the FORTRAN calling sequence are presented in a description section of the MACRO source. Also, both a sample FORTRAN program and user assembly instructions are given. Three applications programs written in FORTRAN are included with the submittal of this handler. They write, WDOSMT, and read, RDOSMT to and from 9-track magnetic tape, respectively. The magnetic tape is in DOS/BATCH format. Complete user in- structions are included as comments within each of these pro- grams. RWMT will rewind and take offline the selected tape drive(s). The subroutine, EXTMT, and the programs, RDOSMT, WDOSMT and RWMT, are executable under both RT-11 and TSX-Plus. N. A. Bourgeois, Jr. / 1738 Sandia National Laboratories P. O. Box 5800 Albuquerque, NM 87185 23-Feb-82