Calculates a checksum of all image bytes. The image structure
    is followed to include only the image bytes into the checksum.
    Invariant data, such as the linker version and the link date, are
    omitted.

    For Integrity servers images (that is, Integrity servers
    formatted files), a CRC checksum is calculated and additional
    information is output to SYS$OUTPUT, including the following:

    o  The resulting full filename and checksums for the image
       segments

    o  The header checksums and the overall image checksum

    The output values are shown in hexadecimal notation. The DCL
    symbol, CHECKSUM$CHECKSUM, shows the result in hexadecimal
    notation.

    For Alpha and VAX images, an XOR checksum is calculated and
    additional information is output to SYS$OUTPUT:

    o  The resulting full filename and checksums for the image
       sections

    o  The header checksum and the overall image checksum

    The output checksum values are in hexadecimal notation. However,
    the result in the DCL symbol CHECKSUM$CHECKSUM is in unsigned
    decimal notation.

                                   NOTE

       For Alpha and VAX images, the unsigned decimal notation
       of the checksum value in the DCL symbol CHECKSUM$CHECKSUM
       retains compatibility with the previous checksum tool.

    The /IMAGE qualifier implies the default file type of .EXE. For
    Integrity servers images, this qualifier also implies the default
    keyword values HEADERS and SEGMENTS for the /SHOW qualifier.