Early MSDOS was designed to make moving 8080 /Z80 CPM programs easy to move to the 8086 based MSDOS. All of the " File Control Block " stuff in MSDOS programming comes from this feature. There were the drive Letters and directories but no sub-directories. Tree structured directories was a MSDOS 2 feature. NEC V20 / V30 8088/8086 clones had a mode to run 8080/ CPM code under MSDOS. Think of it as a CPM box or virtual CPM. The IBM PC used the 8 bit data bus 8088 so they could use the CPM era 8080 IO chips easily. .
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Early MSDOS was designed to make moving 8080 /Z80 CPM programs easy to move to the 8086 based MSDOS. All of the " File Control Block " stuff in MSDOS programming comes from this feature. There were the drive Letters and directories but no sub-directories. Tree structured directories was a MSDOS 2 feature. NEC V20 / V30 8088/8086 clones had a mode to run 8080/ CPM code under MSDOS. Think of it as a CPM box or virtual CPM. The IBM PC used the 8 bit data bus 8088 so they could use the CPM era 8080 IO chips easily. .