Reserved device names DOS

there reserved device names in dos cannot used filenames regardless of extension occupied built-in character devices. these restrictions affect several windows versions, in cases causing crashes , security vulnerabilities.

the reserved names are: con (for console), aux (for auxiliary), prn (for printer) , lst (for lister), introduced 86-dos 0.74. 86-dos 1.10 , pc dos 1.0 added nul. except lst continued supported in versions of ms-dos, pc dos , dr-dos ever since. lst available in oem versions of ms-dos 1.25, whereas other oem versions of ms-dos 1.25 used lpt1 (first line printer) , com1 (first serial communication device) instead, introduced pc dos. in addition lpt1 , lpt2 com1 com3, hewlett-packard s ms-dos 2.11 hp portable plus supported lst alias lpt2 , 82164a alias com2; supported plt plotters. otherwise, com2, lpt2, lpt3 , clock$ (still named clock in issues of ms-dos 2.11) clock device introduced dos 2.0, , com3 , com4 added dos 3.3. multitasking ms-dos 4 supported keybd$ , screen$. dr dos 5.0 , higher , multiuser dos support $idle$ device dynamic idle detection saving power , improve multitasking. lpt4 optional built-in driver fourth line printer supported in versions of dr-dos since 7.02. config$ constitutes real mode pnp manager in ms-dos 7.0-8.0.

aux typically defaults com1, , prn lpt1 (lst), these defaults can changed in versions of dos point other serial or parallel devices. plt reconfigurable well.

filenames ended colon (:) such nul: conventionally indicate device names, colon not part of name of built-in device drivers. colons not necessary typed in cases, example:

it still possible create files or directories using these reserved device names, such through direct editing of directory data structures in disk sectors. such naming, such starting file name space, has been used viruses or hacking programs obscure files users not know how access these locations.