| Child pages (Children Display) |
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Thoughts
- This book can be read out-of-order.
Summary / Highlights
- Preface to the Paperback Edition
- Code is a book about how computers work.
- 1. Best Friends
- 2. Codes and Combinations
- 3. Braille and Binary Cogl€s
- 4. Anatomy of a Flashlight
- 5. Seeing Around Corners
- 6. Telegraphs and Relays
- 7. Our Ten Digits
- 8. Alternatives to Ten
- 9. Bit by Bit by Bit
- 10. Logic and Switches
- 11. Gates (Not Bill)
- 12. A Binary Adding Machine
- 12. But About Subtraction?
- 14. Feedback and Flip-Flops
- 15. Bytes and Hex
- "The word byte originated at IBM, probably around 1956. The word had its origins in the word bite but was spelled with a y so that nobody would mistake the word for bit. For a while, a byte meant simply the number of bits in a particular data path. But by the mid-1960s, in connection with the development of IBM's System/360 (their large complex of business computers), the word came to mean a group of 8 bits."
- Hex is just a convenient / concise way of referring to byte values; it's an alternative to showing the binary representation.
- He explains how to convert bytes to their decimal equivalents.
- He explains how to convert from binary representations of bytes to the octal-representation.
- "In order for the representations of multibyte values to be consistent with the representations of the individual bytes, we need to use a system in which each byte is divided into equal numbers of bits. That means that we need to divide each byte into four values of 2 bits each (that would be base 4) or two values of 4 bits each (base 16)."
- Hex requires more digits than decimal. He says you could create random symbols for these extra digits, but in practice those digits are represented by letters of the alphabet.
- A lowercase 'h' after a number signifies it as a hex number.
- He shows how to convert from hex to decimal and vice versa.
- 16. An Assemblage of Memory (technical)
- This chapter looks good to read. It seems to explain how RAM works.
- 17. Automation - This chapter seems pretty interesting, he seems to explain how a processor works. (technical)
- "...in this chapter, through a progression of ever more sophisticated machines, I will automate the process of adding and subtracting numbers. (...) The final machine in this chapter will be so versatile that it will be able to solve virtually any problem that makes use of addition and subtraction, and that includes a great many problems indeed."
- 18. From Abaci to Chips (generally nontechnical)
- "The carry seems at first to be a little quirk of addition, but in adding machines, the carry is really the central problem. (...) How successfully the carry is dealt with is a key to the evaluation of old calculating machines."
- He discusses Charles Babbage and his Analytical Engine.
- He discusses Herman Hollerith, who was involved in the 1890 US census and had the census-takers punch holes in cards, then had the data tabulated that way instead of by hand.
- "Herman Hollerith also set in motion a long trail of events. In 1896, he founded the Tabulating Machine Company to lease and sell the punch-card equipment. By 1911, with the help of a couple of mergers, it had become the Computing-Tabulating-Recording Company, or C-T-R. By 1915, the president of C-T-R was Thomas J. Watson (1874-1956), who in 1924 changed the name of the company to International Business Machines Corporation, or IBM."
- He discusses a bunch of other developments: the Colossus code-breaking computer, ENIAC, EDVAC
- 19. Two Classic Microprocessors
- 20. ASCII and a Cast of Characters
- 21. Get on the Bus
- 22. The Operating System
- 23. Fixed Point. Floating Point
- 24. Languages High and Low
- 25. The Graphical Revolution
...