Flight computer
A flight computer was a type of manual, hand-held calculation tool, similar to a slide rule. 

This device was sometimes used on board the  during the 2260s. () 

A operations division crewwoman was reading a flight computer as she walked through a corridor aboard the Enterprise in 2266. Around the same time, Bobby walked onto the bridge reading one briefly. () 

Spock later made a number of calculations on one in 2268, while the ship was held in place by a big green hand. ()

External link 
 

Computer technology