- 4/0 refers to printing in full color (CMYK) on one side of printed
- 4/1 refers to printing in full color (CMYK) on one side of printed material with printing in black ink on the backside.
- 4/4 refers to printing in full color (CMYK) on both sides of printed material.
An NCR form, also referred to as a carbonless form, business form and sometimes simply an invoice, is a multi-part printed form that transcribes writing from the top (white) sheet onto the second (canary) and/or third (pink) sheets without the use of electronics.
The process was invented by chemists Lowell Schleicher and Barry Green, working for the NCR Corporation, as a biodegradable, stain-free alternative to carbon paper. [Wikipedia]