This program is to control MAX6921 for IV-18 VFD display 
To control the MAX6921 needs three pin,CLK,LOAD DATA,just like the shift regester
But the difference is MAX6921 is just using 19bit with LSB first.

Another thing is how you connect MAX6921 to the IV-18 tube.
the connection begin from the third one,with a,b,c,e,d,f,g,h,i
then comes with 1~9 digit.
the digit is already inverted(since LSB first)

The program also pack the DS1307 control (https://bildr.org/2011/03/ds1307-arduino/) to provide RTC .  

To enter the current time,just using the COM port and enter S, and you can enter the current time.

Here is the BLOG:(chinese)
https://will-123456.blogspot.tw/2014/01/iv-18-arduino-shield.html