Lesson one, How Computers work -
numbers, letters and code

So far, we've been talking about ones and zeros but how are they used to do the stuff we want to do on the computer?  Let's take a look at text first.  Back in the beginning each computer (there were only 5 in the world) had a different set of ones and zeros to represent text.  One might use 1001011 another might use 0100101.  That meant they couldn't share data.  So, the computer scientists got together (there were only a couple dozen of them) and made a chart so that all computers would use the same set of ones and zero.  That chart was called ASCII or The American Standard Code for Information Interchange. 

  

As you can see each type of character has it's own unique 7 ones and zeros that represent that character.  Whoa, 7 characters!  Aren't there 8 bits in a bite?  As you can see there's a leading zero for each one.  They only need 128 different characters not 255 different characters so they only use 7.

Notice that the character 1 is 00110001.   That value is just random, it doesn't equate to the mathematical value of 1.  There's a difference between the "text" 1 and the "binary" 1.  You will be learning about binary numbers next and they are completely different than the ASCII or text 1 in the chart.  You need to remember that when you are programming because a few different times you add things together they will join instead.   What you will be do is saying to the computer 1 plus 1 and instead of adding them it will give you answer 11 because it joined them, not added them.  I'll cover that later in the programming section but I wanted to mention it here first.

So, in review, when you press the "!" button on your key board the ones and zeros that are placed into RAM are 00100001.  Meaning the eight capacitors for that byte of ram is:  no charge, no charge, charge, no charge, no charge, no charge, no charge, charge being held in the capacitor.

I hope this is all starting to make sense to you.  Next I'll be discussing binary numbers and hopefully your understanding of how computers work will be complete.

The binary lesson is in this linked word document:  Binary Numbers (word document)  Binary Numbers (PowerPoint presentation)