Home / Certification / CompTIA Certifications

Operating Systems

DOS, or Disk Operating System was the first major operating system for PCs. DOS is a 16-bit operating system. DOS supports 11 character filenames, 8 for the file and 3 for the extension, for example, document.doc is a valid DOS filename, while documents.doc is not.

Windows 3.x is a graphical interface for DOS. Windows 3.x is not a true operating system in this sense, it uses DOS as its underlying Operating System. Thus, the features and problems in DOS also effect Windows 3.x.

According to the exam makers, Windows 95 is a true operating system in the sense it isn't an interface for DOS. Windows 95 has its own sets of utilities and features. Though some (including me) would argue Windows 95 is still not a true operating system due to its interdependencies with old code, it is a true O/S on the exam.

System Files

DOS System files include:

Autoexec.bat - contains the commands and programs run at startup.

Config.sys - contains the configuration system files

IO.sys - the commands use to interact with input/output

Emm386.exe - Memory Manager

Himem.sys - Memory Manager

Command.com - contains the internal DOS commands