How Do I Print to Printer With Casio VX-4 C?

[blackjetrock]

I don't have a VX-4 but from a C point of view, %d prints and integer not a float so looks a bit suspicious, you'll maybe get junk, or maybe Casio have a different %d.
Also, stdprn should be defined in stdio.h so you have created a local variable that hides the real stdprn when you define stdprn in that code. try taking out the

FILE *stprn;

line and add in

#include <stdio.h>

if it's not already there.