DosErrClass receives a nonzero return value from another control-program function as input. It then classifies the return value, tells where in the system the error occurred, and recommends a corrective action.

When called by a family-mode application, DosErrClass can return a valid error classification only for errors that have actually occurred. Also, the classifications of a given return value might not be the same for family-mode and OS/2-mode applications.