DOS under OS/2 and Windows DOS

the dos emulation in os/2 , windows runs in same way native applications do. can access of drives , services, , can use host s clipboard services. because drivers file systems , such forth reside in host system, dos emulation needs provide dos api translation layer converts dos calls os/2 or windows system calls. translation layer converts bios calls , virtualizes common i/o port accesses many dos programs commonly use.

in windows 3.1 , 9x, dos virtual machine provided winoldap. winoldap creates virtual machine based on program s pif file, , system state when windows loaded. dos graphics mode, both character , graphic, can captured , run in window. dos applications can use windows clipboard accessing published calls in winoldap, , 1 can paste text through winoldap graphics.

the emulated dos in os/2 , windows nt based upon dos 5. although there default configuration (config.sys , autoexec.bat), 1 can use alternate files on session-by-session basis. possible load drivers in these files access host system, although these typically third-party.

under os/2 2.x , later, dos emulation provided doskrnl. file represents combined ibmbio.com , ibmdos.com, system calls passed through os/2 windowing services. dos programs run in own environment, bulk of dos utilities provided bound dos / os2 applications in \os2 directory. os/2 can run windows 3.1 applications using modified copy of windows (win-os/2). modifications allow windows 3.1 programs run seamlessly on os/2 desktop, or 1 can start winos/2 desktop, similar starting windows dos.

os/2 allows dos drive a: , (vmdisk). real dos, ms-dos 6.22 or pc dos 5.00. 1 makes bootable floppy disk of dos, add number of drivers os/2, , creates special image. dos booted way has full access system, provides own drivers hardware. 1 can use such disk access cdrom drives there no os/2 driver.

in windows nt (2000, xp, vista, 7), dos emulation provided way of virtual dos machine (ntvdm). dos files reside in ntio.sys , ntbio.sys usual, run in virtual machine provided ntvdm. character input passed console session launched dos program. allows 1 use cli features such pipes , redirection between dos , windows nt. os/2 emulation in nt , 2000 similar, no virtual machine loaded: handled os2ss.exe , os2.exe.

64-bit versions of windows not support ntvdm , cannot run 16-bit dos applications directly; third-party emulators such dosbox can used run these programs.