The two best intros on C that I've seen are Stephen Kochan's _Progamming in C_ (or _Programming in ANSI C_ -- same big, updated for ANSI) and Waite et al's _C Primer Plus. For PC-specific stuff, you might want to look at Robert LaFore's _Turbo C Programming for the IBM_. (He also has written _Microsoft C Programming for the IBM_ for those using MSC or Quick C.)