DOS - Disk Operating System)
MS-DOS or DOS was the original Microsoft IBM-PC operating system from 1981. It supports only text commands, and still lurks underneath Windows-95.
Because all applications software depends upon the operating system, customers complain about new versions of the operating system which is incompatible with existing software. Thus Windows 95 has to "fix" problems in such a way that old things still work.
A kludge is an ugly but workable fix. Windows 95 is full of such kludges.
Directories
The operating system controls disk access, and hence controls the file name and directory conventions.
It is very convenient to store files hierarchically into directories, so that we can organize files by their topic.
My files are organized into such directories as "research", "teaching", "book", "administrative", and "letters".
These directories are organized into subdirectories like "teaching/101" and "teaching/373" and then even finer subdirectories like "teaching/101/lectures" and "teaching/101/projects".
The chain of directories to get to a file is called its path name. The root directory has path name "/".
When you are in a particular directory D, it assumes that all names referred to start with the path of D. This saves a lot of typing, and provides the illusion each directory is its own world.
File Names and Extensions
File names are typically given by a string of alphanumerical characters. Different operating systems have different restrictions.
MS-DOS names are up to 8 characters long, with a 3 character extension, like "cse101.txt". Upper case and lower case in interchangable (this is a bug, not a feature). Only a few special characters can be included as names, not ",. .
These restrictions turn filenames into vanity license plate numbers. Many of these restrictions are removed in Windows 95, but the damage has already been done.
Wildcard characters enable one to talk about all files with similar names, like "cse101.*" or "cse*.tex", which is very convenient in operating system commands.
MS-DOS commands
Some typical MS-DOS commands at the A:
> prompt are:
View the contents of a directory, dir c:
dos
Move into a new directory, cd cse101
Move onto a new default drive, a:
Create a new directory, md stuff
Remove a directory, rd stuff
Copy files, copy project1.txt proj1.txt
Remove files, del cse*.*
Other Popular Operating Systems
Windows NT is Microsoft's newest, DOS-free operating system. It is currently intended mostly for multiuser systems, but may eventually merge with Windows 95.
OS/2 is IBM's version of Windows. Many experts feel it is "better", but it had no chance against the Microsoft juggernaut.
UNIX is the ``programmer's operating system'', developed at Bell Laboratories in the early 1970's. It is very powerful for those who know what they are doing. UNIX was the original portable operating system, which could run on many different types of CPUs.