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MS-DOS: Difference between revisions
→DOS kernel
Tag: 2017 source edit |
Tag: 2017 source edit |
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Memory management allows programs to allocate conventional memory at runtime as needed. It is necessary when multiple programs are loaded to make sure that the active program does not overwrite the data of the other programs. However, as MS-DOS runs in real mode, there is no memory protection and therefore the allocations are not actually enforced, unlike protected mode operating systems. | Memory management allows programs to allocate conventional memory at runtime as needed. It is necessary when multiple programs are loaded to make sure that the active program does not overwrite the data of the other programs. However, as MS-DOS runs in real mode, there is no memory protection and therefore the allocations are not actually enforced, unlike protected mode operating systems. | ||
The kernel also implements support for File Allocation Table (FAT) family file systems. The original FAT12 file system was adapted from the file system used by Microsoft Standalone Disk BASIC and used 12-bit cluster indices. In the following versions, it was further improved by adding support for subdirectories, supporting larger volumes, and by extending the FAT to use 16-bit and later 32-bit cluster indices. The file system implementation in the MS-DOS kernel is completely bypassed when using [[Windows for Workgroups 3.11]] or later with 32-bit file access enabled; the VFAT virtual driver that implements the feature was later improved in [[Windows 95]] to support [[w:long file names|long file names]]. | |||
The redirector interface, introduced with MS-DOS 3.1, allows bypassing the FAT file system code to implement a custom file system. This was originally intended to be used by network clients as a means of enabling access to files on other networked computers, although it was eventually also used to implement support for the CD-ROM file system in the Microsoft CD-ROM Extensions (MSCDEX). | |||
Since [[MS-DOS in Windows 9x|MS-DOS 7]], the kernel is merged into <code>IO.SYS</code> and <code>MSDOS.SYS</code> serves as a configuration file. | Since [[MS-DOS in Windows 9x|MS-DOS 7]], the kernel is merged into <code>IO.SYS</code> and <code>MSDOS.SYS</code> serves as a configuration file. | ||