A constructor built out of quantum theory which can replicate itself. It is considered a universal computer.

bit string encoding

encode a finite string in \(\Sigma^{*}\) as a bit string: encoding each character in \(\log | \Sigma |\) bits (by basically IDing each bit).

For \(x \in \Sigma^{*}\), define \(b_{\Sigma}(x)\) to be its binary encoding.

For \(x,y \in \Sigma^{*}\), to encode the pair of strings \(x\) and \(y\), we can encode tuples by adding just a separate symbol \(\Sigma’ = \Sigma \cup \qty {,}\), and then we can write \(x,y\). (if we want to know how long \(x\) is ahead of time we can encode it by show you how long it is through zeros early—\(0^{|b_{\Sigma} (x)|} 1 b_{\Sigma}(x) b_{\Sigma}(y)\).

Unix is a standard set of tools commonly used in software development.

• macOS and Linux are on top of Unix
• Windows comes Unix now lol

You can navigate Unix inside a command line.

its a File Payload Data with smartness.

Notably, the entire file system only supports \(2^{16} = 32MB\) worth of space due to short address types.

For each file on the disk, we store payload data in a bunch of places scattered across the disk, and a single inode which stores the location of each block for the file in an array.