Inferred Dependents and Rules
NMAKE assumes an inferred dependent for a target if an applicable inference rule exists. A rule applies if:
toext matches the target's extension.
fromext matches the extension of a file that has the target's base name and that exists in the current or specified directory.
fromext is in .SUFFIXES; no other fromext in a matching rule has a higher .SUFFIXES priority.
No explicit dependent has a higher .SUFFIXES priority.
Inferred dependents can cause unexpected side effects. If the target's description block contains commands, NMAKE executes those commands instead of the commands in the rule.