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5.1 : The Hardware

HARDware more like CARDware

The CARDIAC is made completely out of cardboard. In fact, one might even say that the CARDIAC is made of cardstock, which is even cheaper than cardboard. The main idea is that there is no big fancy graphics card. There is no face recognition camera. The CARDIAC is a functional computer made out of cardboard, or cardstock if you want to get technical. A main thing to realize is that a computer doesn't always mean a desktop, or a laptop, or a smart phone. When I refer to hardware, I'm referring to what makes up this computer. What are the pieces we put together to make computer, specifically the CARDIAC. I'll give you a hint, it's not just cardboard (or cardstock either).

Organization

There are four major elements to the organization of a computer. We have the Input devices. There are output devices. There's the CPU, or the Central Processing Unit. Lastly, there's the memory. I'll explain each item and then how they each relate to the CARDIAC.

Input

When thinking of a typical desktop computer, what types of devices do we use to input to the computer. Of course there's the keyboard and the mouse. These are preprogrammed devices that automatically translate simple button presses into code that the computer understands. These can include storage devices like disks, tapes and USB flash drives.

In the CARDIAC, the input is a deck. The deck is a deck of cards full of commands and variables and numbers. Back before verbose programming languages, the way humans interacted with computers was very different. People couldn't just talk to a computer. Programmers punched holes in each card to specify a specific command. So for example a 400 line program would be a stack of 400 cards. Below you can see two punchcards. One is from Bell Labs, the people that created the CARDIAC. The other is a FORTRAN puch card from CERN, a European Center for Nuclear Research. As you can see, the punch cards have lines of numbers and letters. For each line of code or command you'd punch in each value and move onto the next card. From there you'd put your deck of cards into the computer and the code would run. The deck of the CARDIAC is a deck of numbers the user inputs. These numbers can be variables or commands or memory locations. The most important thing to recognize is that this deck is just all numbers.

Output

Output devices are plain and simple. It's a device that outputs something for a user. On your typical commercial desktop computer an output device is the moniter or a screen. An output device could also be a printer. On the CARDIAC let's also consider our output device to be a printer. There's no fancy colors or toner you have to buy. All the CARDIAC's "printer" does is print out numbers when it comes across the output operand. That's all it is. There's no fun history behind outputs. Life is full of disappointments.

Memory

Memory is where everything is stored in the computer. Everything is stored as 1s and 0s. It's an array of bytes. There are memory locations 0 through 2n-1. So if n=8 I have 256 memory locations labelled 0-255. In the case of the CARDIAC, we have 100 memory locations numbered 00-99. The CARDIAC is a little different as 100 does not follow the power of two rule. We'll choose to ignore this minor inconvenience. A more pressing problem is the fact is the CARDIAC is cardstock not cardboard. That's my own personal vendetta. I used to work at a craft store.\ \ A big thing to note about memory is how variables interact with memory. Variables are an alias for a place in memory. Variables are NOT what is stored at that memory point. Consider it like mailboxes or PO boxes. There's lots of mailboxes each with their own number and address. If my wonderful mother sends me a letter, it is put inside my mailbox. When I go to retrieve my letter I go to my mailbox, and I get the letter from inside it. I do NOT rip the mailbox from the ground. I do NOT take my mailbox into my house. My mailbox is not the letter. My mailbox is where the letter from my wonderful mother is. The contents of my mailbox can change. Let's say my beautiful boyfriend sends me a equally beautiful letter. Once again this is put in my mailbox. The letter from my mother is no longer inside the mailbox. Now the letter from my boyfriend is in my mailbox. My mailbox is not tied to a specific letter or package. It is free to contain whatever.

Now let's look at variables from a mathmatical standpoint. Variables in math typically hold numbers. Look at the following problem. It's a very simple algebra just to understand how variables work. It is important to know that math is a big part of computer science.

x = 5
x + 2 = y
y = 7
x + y = 12

So above, x is "equal to" 5. I use the words equal to in quotes. Remember, x is not 5, x is where 5 is stored. On a TI-84 calculator, there's a way to make programs. It uses the language TI-BASIC. In TI-BASIC, the way to assign a variable a value, you use the STORE function. It's much easier to remember that variables do not equal it's value this way. So anyway, as you can see, when we add x and y, we do not add the letters and create some mutant xy letter. We refer back to 5 and we refer back to 7 and then we get the answer of 12. It's also important to differentiate between the fact that x + y is equal to 12. 12 is NOT stored in x + y. There is a very big difference between equating two objects and storing a variable. In many programming languages, storing a variable uses the = operator and comparing and equating two values uses the == operator. This is a very common error when programming.

TL;DR Variables are not equal to a variable, they are the alias to where the variable is stored.

CPU

CPU stand for Central Processing Unit. On the CARDIAC there are a few major components

Depending on different instructions in the CARDIAC, different processes will happen. However, there is a general idea that the CARDIAC goes through when it runs programs. The general process goes as follows:

Punch Card Image credit: [Douglas W. Jones's collection of punched cards with logos](https://homepage.divms.uiowa.edu/jones/cards/collection/i-logo.html)

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