Saturday, February 20, 2016

Fundamentals of Computing - Lesson 1 - The Operating System

Nowadays, youngsters think Windows or MacOS (or sometimes Linux) when you talk about computers. The mouse and little icons have become so commonplace that no one considers that there was actually a time when we didn't have these little icons. Back in those days we had an operating system based on commands entered on a command line. That system was MS-DOS, licensed by IBM for their own machines as PC-DOS, and even 'copied' by a competitor as DR-DOS.

Commands - A Quick Overview
When you wanted to know what files were in a directory (what you would know as a Folder), you entered the command


When you wanted to see the content of subdirectories also, you could enter the command


As you will have guessed, you often ended up not being able to read all the files, as their names just ran across the screen, and you would only see the last 20 or so files. Therefore you could ass /P to the command, thus ending up with


You could check the health of your harddrive using the command CHKDSK (standing for Check Disk), and likewise, you could format new discs using FORMAT A: when the disc was in the A-drive, the first drive on your system.

The Drive Letters - A Quick Overview
Drive names had a convention set up along the following system:

A and B - floppy drive letters (3½" containing either 720 kilobytes or 1,44 megabytes and 5,25" containing either 360 kilobytes or 1,2 megabytes)
C through Z - hard drive letters

When you had a cd-rom drive (these could - and still can - contain approx. 650-700 megabytes), you often defined the cd-rom drive as the D-drive using the MSCDEX.EXE program with various additions such as what driver was to be used for MSCDEX to interpret your specific version of the cd-drive you had in your system.

When you had a bigger hard drive, you had often partitioned it into several drives, and thus you would have C and D as your hard drives, and then E as your cd-rom, when you had such a drive, which was not all that commonplace when I bought my first 80286 running at 12mhz with a 65,5megabyte hard drive. :-)

The DOS Operating System - A Quick Overview
When I bought my first computer, it was originally equipped with MS-DOS 3.3. Soon after, the operating system was upgraded to version 5.0 which I bought on I believe it was three discs. DOS stands for Disc Operating System, and was totally command based. DOS in version 5.0 changed this for two programs. Now CHKDSK was replaced with SCANDSK, and we got a defragmentation program, SPEEDSK.

Along the line, DOS appeared in versions 6, 6.2 and finally 6.22. There was also a version 7 which I never got to use, but wanted to add it just for the record.

In the next lesson we will look at how computers work. Stay tuned for more about the fundamentals of computing.

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