C exit from infinite loop on keypress

The function kbhit() from conio.h returns non-zero value if any key is pressed but it does not block like getch(). Now, this is obviously not standard. But as you are already using getch() from conio.h, I think your compiler has this.

if (kbhit()) {
    // keyboard pressed
}

From Wikipedia,

conio.h is a C header file used in old MS-DOS compilers to create text user interfaces. It is not described in The C Programming Language book, and it is not part of the C standard library, ISO C nor is it required by POSIX.

Most C compilers that target DOS, Windows 3.x, Phar Lap, DOSX, OS/2, or Win321 have this header and supply the associated library functions in the default C library. Most C compilers that target UNIX and Linux do not have this header and do not supply the library functions.

If you are using getch() from conio.h anyway, try to use kbhit() instead. Note that both getch() and kbhit() - conio.h, in fact - are not standard C.