From a NAND Gate To Tetris

mikejuk writes "Long before the current crop of MOOCs (Massive Online Open Course) there was a course that taught you all you needed to know about computers by starting from the NAND gate and working its way up through the logic circuits needed for a computer, on to an assembler, a compiler, an operating system, and finally Tetris. Recently one of the creators of the course, Shimon Schocken, gave a TED talk explaining how it all happened and why it is still relevant today. Once you have seen what is on offer at http://www.nand2tetris.org/ you will probably decide that it is not only still relevant but the only way to really understand what computers are all about."

Comments

Logic is Logic

[thejuggler]

Somewhere between learning to write my first "Hello World" program on the Apple IIe (and the TI99/4A) and making a career out of programming years later, I went to schools for Computer Repair and Bio-Medical Electronics. I still have a pile of 7400 series IC chips and my breadboards amongst other electronic components. I learned analog and digital circuit design in the late 80's. The logic learned in those classes still applies to everyday programming today. No matter what I did in those previous careers, the training I did then still applies today. AND, OR, NOT, NAND, NOR, XOR and XNOR are still the 7 basic logic elements that make up all digital electronics and programming. From there Truth Tables are built and boolean algebra is applied to create any and all circuits and code today. In my humble opinion these are still essential to training people new to various IT fields. It's like having to learn nous, verbs, adverbs and adjectives in order to write understandable thoughts. If you lack this basic understanding learning the more advance concepts is difficult at best. It's good to see these are still being taught somewhere.

Re:Logic is Logic

[famebait]

No, but it sums up all the useful/practical ones.
If you only have two inputs, there are only 4 rows in the table,:
| A | B |
| 0 | 0 |
| 0 | 1 |
| 1 | 0 |
| 1 | 1 |

This yields only 16 possible output columns:
0000 - does not vary with input
0001 - AND
0010 - not commutative
0011 - reacts only to A
0100 - not commutative
0101 - reacts only to B
0110 - XOR
0111 - OR
1000 - NOR
1001 - XNOR
1010 - reacts only to B
1011 - not commutative
1100 - reacts only to A
1101 - not commutative
1110 - NAND
1111 - does not react to input

That makes 6 potentialy desirable operations. The seventh is NOT, which takes only one input.
The not commutative ones could conceivably be put to useful work, but in physical designs the asymmetry is impractical, and you can trivially construct them from other gates if need be. In fact some of the useful ones ar also usually constructed from combinations of the others, and all of them *can* be constructed from combinations of NAND gates.