Why 255 is a hard limit in Windows

You may have noticed that 255 often comes up as a hard limit in computing again and again.

A short text field in a MS Access database cannot be more than 255 characters.

It is not possible to search for more than 255 characters in the MS Word find tool.

And of course as discussed in the Tip of the Night for December 22, 2019, the number of characters in a single file path that can be accessed by Windows Explorer cannot exceed 255.

Why is 255 the numerical limit? It has to do with 8-bit computing. Compuer systems use binary code - a series of 0s and 1s to represent values. So for example, a lower case 'x' in binary code will be represented as 01111000. A combination of zeros and ones is used to represent letters and numbers. The earliest computers had 8 bits to a byte - so the most basic data blocks could have no more than 255 characters - two to the eight power, 2^8 equals 256. Modern computers can use 64-bit data blocks, which can represent a far greater number of values (2^64 equals 18446744073709552000). However, software devs often design programs so that they don't take up more storage space than necessary - and the smallest possible storage spaces are 8-bit blocks. The limit of 255 is imposed, so larger 32-bit or 64-bit data blocks are not taken up.

finding the last time a PC was started

If you want to find out the last time a Windows 11 PC was powered on, or shut down you can use the Event Viewer application.

Bring up Event Viewer by searching for it Windows. It will be preinstalled.

In Event Viewer, open the Windows Log menu and click on 'System'

Bring up 'Filter Current Log' from the Actions pane on the right. Enter '6005' in the Event ID field.

You can sort in the results by the date and time to find the latest time the PC was started.

Use 6006 as the Event ID to find when the PC was shut down.

Getting rid of those pesky .db files

The Litigation Support Tip of the Night for February 7, 2017 described how to remove thumbnail image files which could not be deleted through the normal right click process. Lately I have found when working in Windows 11 that the technique of deleting the files in the 'Content' view no longer works. I get an error message like this:

This week I was able to successfully implement the solution posted here by Anand Khanse which recommends a change in the Registry Editor. Browse to HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows and right click and select New . . . Key

Create a new folder named, 'Explorer' and then right click on it and again select New

. . . select the option for 'DWORD (32-bit) Value', and name the DWORD as DisableThumbsDBOnNetworkFolders

If you double-click on this file a dialog box will open which allow you to set the value data to 1

When I made this change in RegEdit I was able to successfully delete thumbnail .db file after I rebooted Windows.

As always exercise great caution when making changes in Registry Editor.