Answer: MSDOS

AnswerCrossword Clue
MSDOSPC software of old
MSDOSOld PC operating system
MSDOSIt worked with a prompt
MSDOSPC platform popular in the '80s
MSDOSUnderpinnings of Windows 1.0
MSDOSWindows underpinning
MSDOSEarly PC go-with
MSDOSComputer operating system of old
MSDOSEarly operating system developed for PCs
MSDOSWhat we opened before we had Windows
MSDOSEnvironment of many old PCs
MSDOSIt was booted before Windows
MSDOSPCs once ran on it
MSDOSEarly I.B.M. PC standard
MSDOSIt was run in the 1980s-'90s
MSDOSPC platform of old
MSDOSIt ran on many clones
MSDOSOnce-popular platform
MSDOSWhat we used before Windows
MSDOSIt was opened before Windows
MSDOSCommon computer interface
MSDOSPC system of the past
MSDOSPredecessor of Windows
MSDOSWindows superseded it
MSDOSPlatform with a FAT file system
MSDOSUser interface
MSDOSA PC may use it
MSDOSComputer acronym
MSDOSEarly IBM PC go-with
MSDOSIt helps many machines run
MSDOSOperations were once commonly performed in this
MSDOSOld PC installation
MSDOS1980's PC's ran on it
MSDOSPC software
MSDOSKind of PC command
MSDOSPC program
MSDOSOld PC standard
MSDOSMany PCs once ran on it
MSDOSPC platform released in 1982
MSDOSIt worked from a prompt