CTSS is developed by MIT computation centre under the direction of Fernando Corbato. In the 1960’s there was an increase in the amount of people that need computers, therefore time sharing systems could support many users by sharing the computer with many users. CTSS is based on a modified IBM 7094 mainframe computer. Programs created for CTSS are RUNOFF, an early text formatting service and an early inter-user messaging system that presaged email. CTSS operate- until 1973.