Syntax: .PRECIOUS : targets...
This pseudotarget tells NMAKE not to delete a target even if the commands that build it are terminated or interrupted. This pseudotarget overrides the NMAKE default. By default, NMAKE deletes the target if it cannot be sure that the target was built successfully.
For example,
.PRECIOUS : TOOLS.LIB TOOLS.LIB : A2Z.OBJ Z2A.OBJ command :
If the commands to build TOOLS.LIB are interrupted, leaving an incomplete file, NMAKE does not delete the partially built TOOLS.LIB.
Note: The pseudotarget .PRECIOUS is useful only in limited circumstances. Most professional development tools have their own interrupt handlers and "clean up" when errors occur.