This new computer program makes printers work twice as fast computer is used how in this sentence.
In that sentence, "computer" is used as either an adjective modifying the noun "program" or part of a two-word compound noun -- "computer program."
I'd go with the first one, though.
In this sentence, the word "computer" is used as an adjective to describe the type of program that is being referenced. The program being described is specifically designed to make printers work twice as fast.
To understand the sentence, you can break it down into its components:
Subject: This new computer program
Verb: makes
Object: printers work twice as fast
The phrase "computer program" is used to describe the type of program being referenced, indicating that it is a program designed for use on a computer. Specifically, this particular program has the capability to make printers work at twice their normal speed.