Approximately two and a half years ago we started to design a comprehensive computer controlled system to handle data and control telescopes at the Hale Observatories. Our previous experience with hard-wired digital data systems had adequately demonstrated that digital systems can increase the astronomical observer’s efficiency by at least a factor of two, that is, we had found that our observers, when using these digital data systems were able to observe twice as many stars per night as they had previously. We became painfully aware of the fact that the hard-wired systems were extremely difficult to modify for new observing requirements. It therefore appeared logical to develop a data system using a small computer which had the facility of permitting the addition of a large number of new devices without modifying the hardware which had been previously constructed. This concept has the advantage that new observing instruments can be added by constructing new hardwire peripheral devices and developing new software. During the development time of a new device it is always possible to insure that the instrument can be returned to its previous configuration by loading the computer with its previous program. This permits an observer to use the same equipment configuration for a period of years even though the capability of the basic system has been greatly enlarged.