Mark I Fire Control Computer The Mark 1 , and later the Mark 1A , Fire Control Computer was a component of the Mark 37 Gun Fire Control System deployed by the United States Navy during World War II and up to 1969 . It was used on a variety of ships , ranging from destroyer s ( one per ship ) to battleship s ( four per ship ) . The Mark 37 system used tachymetric target motion prediction to compute a fire control solution . Weighing more than 3000 pounds ( 1363 kilograms ) , the Mark 1 itself was installed in the plotting room , a water tight compartment that was located deep inside the ship ' s hull to provide as much protection against battle damage as was possible . Essentially an electromechanical analog computer , the Mark 1 was electrically linked to the gun turret s and the Mark 37 gun director , the latter mounted as high on the superstructure as possible to afford maximum visual and radar range . The gun director was equipped with both optical and radar range finding , and was able to rotate on a small barbette - like structure . Using the range finders , the director was able to produce a continuously varying set of outputs , referred to as line - of - sight ( LOS ) data , that were electrically relayed to the Mark 1 via synchro motors . The LOS data provided the target ' s present range , bearing , and in the case of aerial targets , altitude . Additional inputs to the Mark 1 were continuously generated from the stable element , a gyroscopic device that reacted to the roll and pitch of the ship , the pitometer log , which measured the ship ' s speed through the water , and an anemometer , which provided wind speed and direction . In " Plot " ( the plotting room ) , a team of sailors stood around the Mark 1 and continuously monitored its operation . They would also be responsible for calculating and entering the average muzzle velocity of the projectile s to be fired before action started . This calculation was based on the type of propellant to be used and its temperature , the projectile type and weight , and the number of rounds fired through the guns to date . Given these inputs , the Mark 1 automatically computed the lead angles to the future position of the target at the end of the projectile ' s time of flight , adding in corrections for gravity , relative wind , the magnus effect of the spinning projectile , and parallax , the latter compensation necessary because the guns themselves were widely displaced along the length of the ship . Lead angles and corrections were added to the LOS data to generate the line - of - fire ( LOF ) data . The LOF data , bearing and elevation , as well as the projectile ' s fuze time , was sent to the turrets by synchro motors , whose motion actuated hydraulic machinery to aim the guns . Once the system was " locked " on the target , it produced a continuous fire control solution . While these fire control systems greatly improved the long - range accuracy of ship - to - ship and ship - to - shore gunfire , especially on heavy cruiser s and battleships , it was in the anti - aircraft warfare mode that the Mark 1 made the greatest contribution . However , the anti - aircraft value of analog computers such as the Mark 1 was greatly reduced with the introduction of jet aircraft , where the relative motion of the target became such that the computer ' s mechanism could not react quickly enough to produce accurate results . The design of the post war Mark 1A may have been influenced by the Bell Labs Mark 8 , Fire Control Computer which was developed as an all electrical computer , incorporating technology from the M9 gun data computer as a safeguard to ensure adequate supplies of fire control computers for the USN during WW2 . Surviving Mark 1 computers were upgraded to the Mark 1A standard after World War II ended . Digital fire control computers were not introduced until the age of minicomputers in the mid - 1970s .