DECUS 12-138 ISEL

This document is a write-up for a program named ISEL, identified as DECUS No. 12-138, from the DECUS Program Library.

Authored by Larry Davis of Washington University and submitted by Robert Hassinger of Liberty Mutual Research Center, it was created on October 19, 1972, and is written in SABR.

ISEL is a FORTRAN or SABR callable function designed to check the status of a specified LINCTAPE unit. It returns a value indicating the unit's condition:

• -1: If the LINCTAPE unit is not selected.
• 0: If the LINCTAPE unit is selected but not write-enabled.
• 1: If the LINCTAPE unit is both selected and write-enabled.

This functionality is intended to allow programs to check a LINCTAPE unit's readiness before performing operations, enabling them to print informative messages if the unit is not in the desired state.

The document also clarifies that ISEL is a user program, not subject to DECUS quality control, and is provided without warranty or responsibility from DECUS for its accuracy or functioning.