Directory vs. Database

I finished that last AV job. It was a temporary position. I liked it well enough in the way that I enjoyed learning what I do not want to do with my life. The people were nice, the work was all right, but I want something far more social engaging, physically active, and mentally challenging. With that, I am job searching. I keep finding a lot of interesting jobs that I feel I would do well in -and all of them require knowledge of directory services and/or Active Directory specifically. This seems to be a giant, gaping whole in my knowledge of computers, so here I am to figure it out.

What is a directory service?

Initially it always seemed like a directory was a form of a database, but the article I'm trying to learn from makes it seems like directories and databases are distinct things. They mark out a few differences in the construction and use in order to demonstrate to the student how it differs. I will try from memory first to outline these differences then fix it afterwards.

Hierarchal construction in directories vs. geometrical construction of databases:

Perhaps with this non-sense it shows I'm still trying to figure out databases, too. I also couldn't figure out a word to describe what I know of databases' non-hierarchal, but also non-chaotic nature. I see them as blocks of information and then when you get into relational dbs, you start to draw lines in the diagrams when drawing your dbs designs, thus...geometrical *shrugs* It's all I got haha. Directories are hierarchal though from what I understand in that you have an information type and then you have subtypes of that information -kind of like an outline consutrcted during the plot/story design of a book or essay (and unlike this blog which is non-hierarchal, and most definitely chaotic).

Interaction via protocol (directories) vs. API (database)

Directories specifically are good for sharing information between various applications for use in a variety of contexts. Databases are designed and controlled with an API of some language and thus are application specific.

Those are the only differences I can remember. Also this does not answer the initial question -what is a directory *service*? This begs the question...are there database services? Services are another huge part of computing that I know almost nothing about -perhaps I should be exploring what this is first.

Digital Logic - Reviewing Truth Tables and Transistors

Goal:
Create a calculator with basic single digit addition on a breadboard.

Knowns:
There are various gates made of different transistor combinations. The most common are:
   a. AND
   b. NOT
   c. OR
   d. XOR
   e. NAND
Please let me know if I have forgotten a common one.

A truth table is a table of inputs into a circuit and outputs after the corresponding inputs have been processed by the overarching logic path or set of gates the inputs go through. A circuit can have multiple combinations of inputs (consisting of either 0 or 1) and types of gates that those 0 or 1 inputs are modified by (AND, OR, NOR, etc...). For example a single NOT gate takes one input of 0 or 1. If input 1, but run it through a NOT gate, the output is NOT 1, but 0. Alternately if you input 0 into a NOT gate, then it will come out NOT as 0, but as 1. This is what the truth table for a NOT gate looks like.

NOT
Input (I) | Output (O)
    1                   0
    0                   1

Some gates take two input. Each of these gates handles each combination of input types differently. For example, if you take 1 AND 0, you get 0. However, if you take 1 OR 0, you get 1. There are truth tables to help lay out the full mathematical modification. This type of math is call boolean algebra. This isn't your normal adding, subtracting, multiplication and division -that is arithmetic. I have included the full truth tables for AND and OR as well. Now that you know what to search for online, you can learn more about digital logic -the language behind circuits and electronics. As a note before you research more, sometimes instead of saying "input" or "I", a truth table will use "p" and "q" for multiple inputs and use "z" or "r" or all kinds of other things for an output. The key for the output is that it'll always be the on the farther right and there'll always only be one.

AND
I.1 |  I.2 | O
 1      1     1
 0      1     0
 1      0     0
 0      0     0

OR
I.1 | I.2 | O
 1      1    1
 1      0    1
 0      1    1
 0      0    0

A normal transistor is simply a physical device that either lets through a flow of something or not. Like a draw bridge that goes up and down. When it is lowered, flow of traffic between a castle and the outside can happen; when it is raised, the flow of traffic in and out stops. In circuits this is instead electrons (negatively charged particles normally found in an atom) flowing around the gold, silver or copper (metals -which are conductors).

I've been writing this post for a few days and finished the bulk so I'm gonna stop here for now and work on my next one.

Mindy R. Bowen