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The MS-DOS and Older Windows Operating Systems | |||||
---|---|---|---|---|---|
Operating
System |
System Access |
Available Active Processes |
Addressable
Memory |
Contents of Segment
Register |
Word Length |
MS-DOS and Windows real mode | Direct to hardware and OS call | One | 1 megabyte |
Actual
address |
16 bits |
Windows 3.x virtual-86 mode | Operating system call | Multiple | 1 megabyte |
Segment
selectors |
16 bits |
Windows 3.x protected mode | Operating system call | Multiple | 16 megabytes |
Segment
selectors |
16 bits |
Windows NT 3.x | Operating system call | Multiple | 512 megabytes |
Segment
selectors |
32 bits |
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