Code: The Hidden Language of Computer Hardware and Software, by Charles Petzold, is a well-written and wonderfully detailed introduction to how computers work. It starts with a gentle introduction to binary encodings via Morse code and the telegraph, and then proceeds to build a computer from the ground up from relays to logic gates to circuits to memory to a real CPU. The book does not require any prerequisite knowledge and is fully self-contained, although it becomes increasingly complex at the end as each chapter needs the reader to fully understanding the material that came before it. To anyone interested in computers, the first $n$ chapters will be an accessible and enlightening read for some $n$, and I highly recommend it.

On my first read of the book, $n$ was 16 (19 in the second edition). I already knew how logic gates could be networked to compute an arbitrary Boolean function, but didn’t see how that could be extended to a fully programmable computer. As Code explains, the key step is to design a feedback circuit that admits multiple stable states. Such a circuit can be used to build a memory array to store data — including “instructions” that can be read conditionally execute other circuits.

Most Chinese languages, such as Mandarin and Cantonese, pronounce 茶 along the lines of cha, but Min varieties along the Southern coast of China and in Southeast Asia pronounce it like teh. Almost all languages use variants of one or the other, depending on who they got their tea from.

• The Portuguese borrowed chá from Cantonese in the 1550s via their trading posts in Macau.
• The Persians adopted chay from Mandarin, which spread throughout Central Asia.
• The Dutch may have borrowed their word for tea through trade directly from Fujian or Taiwan, or from Malay traders in Java who had adopted the Min pronunciation as teh.
• The Dutch word influenced other European languages, including French (thé), Spanish (té), German (Tee), and English, even after the latter started buying tea directly from Cantonese-speaking merchants

Several articles pointing this out have the headline “Cha if by land, tea if by sea”. This plays on Longfellow’s poem about Paul Revere, in which lanterns are to signal how the British invade: one if by land, and two if by sea.