At work, I have used spreadsheets as a simple way to make a daily and monthly schedule. For a while I have wanted to use Excel’s functionality to make my schedules smarter and one simple way would be to count the number of hours each individual employee works.  A couple of months ago I attempted this using the COUNTIF function, but I gave up after several hours of trying to copy the formula to other cells.  You see, Excel has this nasty habit of trying to think of what the user is wanting to do and doing it for them.  When I tried copying the formula, Excel would transpose the range of cells used in the formula, thinking I wanted a different range for the new cells.  I went back and edited the range in each cell individually, but this was quite time consuming and when I had to add new employees, I eventually gave up on using that due to time constraints. 

I kept thinking all the time, there must be a way to prevent Excel from transposing the range, but could never find any information on the subject.  In pops my wife and shows me that if you add a dollar sign($) in front of the row identifier then the rows will not update.  It’s the same for the column identifier too.  For instance if you have a formula with the identifier B2 and you don’t want the column to change but you want the row to change, then just use $B2 and when you drag the cell the B will stay the same and the 2 will update depending on which way you drag it.  If you don’t want either to change then use $B$2 and voila your formula will always reference B2, no matter where you drag it.  Man my wife is so smart and wonderful.

As an added bonus, I will tell you how to use a value contained in a cell in a formula.  Part of my scheduling spreadsheet would use the name typed into the first column within the counting formula.  For a time I couldn’t figure out how to reference that value and had to hard code the name into the formula which prevented me from reusing the formula on other rows.  My wife, to the rescue again, tells me about the TRIM function. By using TRIM($A32), will reference in value in cell A32 and since we added the dollar sign the A value will not change when you drag the formula down to other rows.

So there are some very handy things I learned today. I hope they might be helpful to others.

Basically Screenr is an easy way to record what ever is happening on your computer screen, including narration, and send to everyone following your Twitter feed and also save it to the Screenr website for viewing at a later time.

Now here’s the where the magic happens.  If you have a tablet PC, you can record everything you right down on your virtual whiteboard as well as everything you say and then send it to all of your students so they can review everything you discussed in class.  That is simple amazing.  I got the idea from this screencast.

Well there you go.  Put that in your knowledge pipe and blow it.

http://agentzlerich.blogspot.com/2008/07/using-gnu-screen-with-gnome-terminals.html

Once I found out about Screen and learned the interface, it has been immensely helpful, from having multiple game servers running in different screen sessions to being able to work remotely without fear of being disconnected in the middle of doing something.

I thought I’d share some of the things I’ve been working on.  I’m taking a system archetecture class which is really neat.  It’s interesting learning all of the things you can do with 1s and 0s.  The premise of the class is we are going to learn how to design these circuits and eventually put them all together to make a programmable computer.  We use a program called Logisim to design the circuits.

Here are some of the circuits I’ve designed.

Full adder

This one will take a two 1-bit numbers and add them together and if both numbers are 1 it will have a carry out, which is helpful when adding multi-bit numbers. With Logisim once you design a circuit, you can use it in another circuit.  That helps when designing complex circuits. By using divide and conquer, if you break a complex problem into simple steps it makes problem solving a whole lot easier.  With the adders, I had to eventually design a 16-bit adder, which was easy by first designing a 1-bit adder and then incorporating that chip into a 4-bit adder and then incorporating that chip into a 16-bit adder.

4-bit adder

16-bit adder

I then used the 16-bit adder chip in the design of an Arithmetic Unit, or AU, which is one part of the Arithmetic Logic Unit, or ALU for short, a very important part of a computer.

Arithmetic Unit

This unit can do more than add. It can subtract, increment and transfer.  I won’t go into the complexities of those operations, but if you are interested here’s a tutorial on doing 1s and 2s compliement arithmetic.

I bet you can’t guess what is the other part of the ALU? That’s right it’s the Logic Unit, or LU.

Logic Unit

It was a whole lot easier to design than the AU.

We put these all together and what do we get?

Arithmetic Logic Unit

So that’s what I’ve been working on for the past few weeks and I see that this post has grown rather tall so I’ll end it here. 

Until next time, stay frosty.

Now this final project might blow your socks off, so be sure to have your seatbelts fastened before playing it. Here’s the link.

Now understand, I only worked on this program for a couple of days so if it zigs when you zag don’t get upset. I’m lucky I demonstrated it before this guy did.

http://marcospcmusica.wordpress.com/2008/08/03/amigaos-un-disco-de-musica-libre/

It’s all free music and is very good in my opinion.

My friend pointed out a tiny little thing you must do to run the game. You must have the pygame module installed to run it, but hey any serious gamer should already have that. Ha ha ha.

Let’s see. The story so far…

Finished the book Pattern Recognition by William Gibson. Which is ironic because I finished another Gibson book, Neuromancer, almost a year ago exactly. I guess I can update my reading pace from glacier to snail. I want to expand more on Pattern Recognition in a later post, but for now I can say it was a good read. Slightly science fiction, slightly not.

Watched Fools Gold(2008). It was not quite as bad as the rating it got. It’s just sort of your typical romantic/adventure movie and Matthew McConaughey gets hit in the head a lot.

Watched Charlotte Gray (2001). A very interesting tale of a lady who volunteers to be a courier behind enemy lines in occupied France during World War II, in hopes to find her lover who was shot down. It is not a sappy romantic drama, though I do find it hard to believe she would take this risk for someone she recently met. I suppose the story is a little hard to grasp, because so many awful things happen and yet has a fairytale ending, but that’s crazy, liberal Hollywood for you.

Finally watched Alien Vs. Predator Requiem (2007). Which was just awful, but that’s okay because I expected it to be, so shame on me. So if you like implausible storyline, even on the Predator or Alien homeworld, I would recommend watching it. Though I would not recommend watching this, if you have a tendency to scream at the tv screen. Your vocal cords will walk out on you.