The codes are always in the low order byte of the low order word of the reference constant.  The high order byte of the low order word is used for extra data by some codes.  And the high order word is used for dialog (DLOG) IDs for those codes that operate on dialogs.

•  0 – NoOp – The control does nothing.

•  1 – DisposeAdvance – Disposes of current dialog, then opens specified dialog.

•  2 – DisposeRetreat – Disposes of current dialog, then lets previous dialog come to front.

•  3 – Increment – Increments value of control (thus changing the picture it displays).  When value exceeds the maximum, it is reset to the minimum and the process continues.

•  4 – Quit – Exits the application.

•  5 – Advance – Opens the specified dialog.