[colejohnson66]

Does it have to do with how, in BCPL (one of C’s ancestors), everything was basically an integer? So everything is an integer unless told otherwise?

[boomlinde]

Specifically, everything is an integer with the auto lifetime (gets discarded with the stack frame) unless otherwise specified.

I think most modern compilers will warn on encountering such short hand due to the common error of accidentally declaring integers when you meant to assign a value to a variable you forgot to declare.