Library /sys$common/syshlp/pca$help.hlb FIRST, Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    The FIRST command is one of a series of directional commands
    that allows you to traverse a program's structure. The FIRST
    command displays the current traverse subtree and positions
    an arrow to point to the bucket with the most data points. The
    corresponding source lines for that portion of the program are
    displayed alongside the plot. Other traverse commands are NEXT,
    BACK, and CURRENT.