Computer science: Perl programming: chr() function

Tutoring computer science, character operations with ASCII surface. The tutor mentions Perl’s chr() function.

The common English characters one might imagine all have ASCII codes. Tab is 9, Newline is 10, Space is 32, and from 33 to 126 are the visible symbols like a, A, 9, (, etc.

Perl chr()will print the ASCII character for the number it’s given. For intstance,

print "$the_char";

will output the letter H.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Windows, home computer use: command prompt file operations: xcopy

Maintaining a home computer requires frequent self-tutoring. The tutor shares.

This Windows 7 computer no longer performs the COPY command from the mouse, so I use the command prompt to copy files, etc.

Lately I’ve been backing up directories, which contain subdirectories and so on. (Directory can also be thought of as Folder.)

To copy an entire directory, including its subdirectories and the folders contained therein, I use the xcopy command:

xcopy source_directory destination_directory /e


xcopy source_directory destination_directory /s

With /e it copies the empty folders, but not with /s.

In my experience, assigning a destination directory is important, since xcopy doesn’t copy the enclosing directory itself, just its contents. So, for instance, if you want to copy the directory desktop0 to a backup called desktop0, you might key

xcopy the_source_path\desktop0 the_destination_path\desktop0 /e


  1. Although you can use the forward slash to navigate in Windows, it can’t (in my experience) be used in paths in Windows commands. Rather, the backslash must be. For instance, topdir\dir1\dir2 must be used, rather than topdir/dir1/dir2, within a file command such as xcopy. However, for switches such as /s or /e, the forward slash is used.
  2. You can’t use xcopy from within a directory you’re telling it to copy. I typically do it from the one above.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

English, botany: what is a pomologist?

More self-tutoring: the tutor shares a term he discovered today.

pomologist (noun):
one engaged in pomology, which is the science occupied with fruit itself, and/or its production.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Home computer use, computer maintenance, Windows: disk management: how to use unallocated space on a storage device

Home computer use, for me, leads to constant self-tutoring. The tutor shares a video about Windows disk management that he was lucky to find.

My experience: On an external hard drive, if Windows calls a part of it “unallocated”, you can’t store there.

What if you need the unallocated space? One option is to extend the adjacent partition (assuming it’s functional) so that it annexes the unallocated space for use.

In this video, David shows how to extend a useful partition so that it overtakes the unallocated space, making it, too, available for storage.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

English: vocabulary: what does idiosyncrasy mean?

Tutoring English, meaningful words are always interesting. The tutor mentions idiosyncrasy.


idiosyncrasy (noun):

a surprising habit or way of thinking noticed in a mainly “ordinary” individual.

I heard the word idiosyncrasy periodically during the 80s, but never hear it now.


Gilmour, Lorna (editor). Collins Essential Canadian English Dictionary & Thesaurus. Glasgow: HarperCollins Publishers, 2006.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Windows: file permissions: what does Bypass Traverse Checking mean?

Researching file permissions can mean self-tutoring. The tutor relays the idea of Bypass Traverse Checking.

Bypass Traverse Checking (file permission)

This permission allows a user to access a specific file that is not protected, but which resides in a folder the user does not have clearance to examine.

Under the Bypass Traverse Checking permission, the user can navigate to that specific file by its full path designation, without the operating system checking the user’s clearance regarding the containing folder. However, without the necessary clearance, the user cannot simply enter the folder.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Calculator usage: negative numbers to rational exponents (with odd roots)

Tutoring high school math, scientific calculators are a permanent fascination. The tutor mentions a quirk many might share.

Due to

and the fact that a common exponent notation is


it follows that


Curiously, of all the calculators in front of me this moment, only two – the Casio fx-991ES PLUS C and the TI-83 Plus (a graphing calculator) – are willing to perform (-8)^(2/3) as presented. The others give “ERROR”.

Yet, invoking the rule shown above, we can rewrite the calculation as


Then, all the scientific calculators I have at hand will give the answer 4. However, the calculator aboard my mobile phone will only do so if the square is posed before the cube root.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC

English: what does normative mean?

Tutoring English, vocabulary is always interesting. The tutor defines normative.

normative (adj):

either setting a standard or following one.

The principal watched students perform skateboard tricks in the hall. He observed that, while spectacular, their behaviour wasn’t normative.


Barber, Katherine, et al. Oxford Canadian Dictionary of Current English. Don Mills: Oxford University Press, 2005.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Handyman role, home maintenance: (at least some) LED bulbs not for installation in completely enclosed fixtures?

Home maintenance, for me, requires constant self-tutoring. The tutor mentions a message he saw on the label of some LED bulbs.

I long ago heard that LED bulbs would produce comparable light – or even brighter – for a fraction of the energy needed by incandescent bulbs. Last night I installed one and the claim seems true: at 9.5W, the light seems to produce at least as much as I’d expect from a traditional 60W incandescent bulb.

Yet, a directive on the box of the LED bulbs says “not for use in totally enclosed luminaries.” I wondered what it meant, and why. All I could imagine was that heat buildup in an enclosed fixture might compromise the LED function. Yet, isn’t the point of LED bulbs, that they barely produce any heat, so therefore are very efficient?

On the internet I went to and got an answer I’m happy with:

Yes, it’s true the LED bulb shouldn’t be used in a completely enclosed fixture, if the box warns against it. The reason is that, while LED bulbs barely produce any heat, they can be VERY sensitive to heat, so may not function optimally in their own waste heat. An open fixture will allow the heat to escape so that the LED’s function will be promoted.

Fortunately, the fixture in which I wanted to install the LED bulb isn’t completely enclosed: I went ahead with the installation.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Spreadsheets: Excel: the pi() function

Tutoring math, your curiosity naturally extends to spreadsheets. The tutor points out a neat feature of Excel.

If you type


in a cell, the value of π will appear. I find that 14 decimal places are available.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.