(BOS) An early [when?] IBM {operating system}.According to folklore, BOS was the predecessor to TOS on the IBM 360 and it was IPL' d from a card reader.It may have been intended for very small 360' s with no disks and limited tape drives.BOS died out really early [when?] as disks such as the 2311 and 2314 became common with the IBM 360, whereas disks had been a real luxury on the IBM 7090.(1999-01-29)