  The Advanced Photon Source (APS) linear accelerator has two thermionic
cathode rf guns and one photocathode rf gun. The thermionic guns are used
primarily for APS operations while the photocathode gun is used as a
free-electron laser (FEL) driver. With each gun requiring a different lattice
and timing configuration, the need to change quickly between guns puts great
demands on the accelerator operators. Using the Procedure Execution Manager
(PEM), a software environment for managing automated procedures, we have made
start-up and switch-over of the linac systems both easier and more reliable.
The PEM is a graphical user interface written in Tcl/Tk that permits the user
to invoke "machine procedures" and control their execution. It allows
construction of procedures in a hierarchical, parallel fashion, which makes for
efficient execution and development. In this paper, we discuss the features and
advantages of the PEM environment as well the specifics of our procedures for
the APS linac.
