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cyber journey

#code

28 entries across collections.

Code: Best Friends

Code ch. 1 — Morse code as a first code: dots, dashes and timing, why common letters are short, and what a code actually is.

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Code: Codes and Combinations

Code ch. 2 — counting Morse combinations, why two symbols of length n give 2ⁿ codes, and decoding with a binary tree.

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Code: Braille and Binary Codes

Code ch. 3 — Braille's six-dot cells as a binary code, 64 combinations, and shift/escape codes that change what the next symbol means.

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Code: Anatomy of a Flashlight

Code ch. 4 — a circuit from battery, bulb and switch: voltage, current, resistance, Ohm's law, power, series vs parallel, conductors and insulators.

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Code: Communicating Around Corners

Code ch. 5 — signalling by wire between houses: circuits need a return path, shared commons and earth grounds, and why long wires dim the signal.

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Code: Logic with Switches

Code ch. 6 — Boolean algebra (AND, OR, NOT), sets and conditions, and how switches in series and parallel perform logic.

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Code: Telegraphs and Relays

Code ch. 7 — the telegraph key and sounder, why long lines fail, and the relay: a switch flipped by electricity that regenerates the signal.

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Code: Relays and Gates

Code ch. 8 — building AND, OR, NOT, NAND and NOR gates from relays, truth tables, gate symbols and De Morgan's laws.

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Code: Our Ten Digits

Code ch. 9 — why we count in tens, Roman numerals vs positional notation, the importance of zero, and how place value works in any base.

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Code: Alternative 10s

Code ch. 10 — counting in other bases: octal, base 4 and binary, converting between them, and where octal still shows up in Linux permissions.

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Code: Bit by Bit by Bit

Code ch. 11 — the bit as a yes/no answer, 2ⁿ possibilities, how many bits a choice needs, barcodes with check digits, and QR codes.

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Code: Bytes and Hexadecimal

Code ch. 12 — the 8-bit byte, nibbles, hexadecimal digits and conversion, hex notation, and where hex appears in everyday IT.

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Code: From ASCII to Unicode

Code ch. 13 — text as numbers: Baudot and shift codes, 7-bit ASCII and control characters, code pages, Unicode, and UTF-8/16/32.

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Code: Adding with Logic Gates

Code ch. 14 — binary addition, XOR, the half adder and full adder, chaining them into an 8-bit ripple-carry adder, and overflow.

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Code: Is This for Real?

Code ch. 15 — from mechanical calculators and relay machines to vacuum tubes, transistors, integrated circuits and the microprocessor.

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Code: But What About Subtraction?

Code ch. 16 — subtracting with an adder: nines' complement, ones' and two's complement, signed numbers, and overflow.

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Code: Feedback and Flip-Flops

Code ch. 17 — feeding outputs back to inputs: the oscillator (a clock), R-S flip-flops, D latches, edge-triggered flip-flops, dividers and counters.

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Code: Let's Build a Clock!

Code ch. 18 — a digital clock from counters: binary-coded decimal, dividing a fast oscillator down to 1 Hz, and driving seven-segment displays.

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Code: An Assemblage of Memory

Code ch. 19 — building RAM from latches: addresses, decoders to write, selectors to read, address lines vs capacity, and why RAM is volatile.

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Code: Automating Arithmetic

Code ch. 20 — adder plus memory plus a counter: stepping through memory automatically, then storing instruction codes alongside data.

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Code: The Arithmetic/Logic Unit

Code ch. 21 — the ALU: add/subtract plus AND, OR, XOR selected by a function code, with status flags for carry, zero and sign.

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Code: Registers and Busses

Code ch. 22 — registers as fast on-chip storage, the data/address/control busses that move bytes around, three-state buffers, and the fetch-execute cycle.

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Code: CPU Control Signals

Code ch. 23 — the control unit: turning opcodes into the timed signals that steer registers, ALU and memory, instruction sets and microcode.

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Code: Loops, Jumps, and Calls

Code ch. 24 — changing the program counter: unconditional and conditional jumps, loops, the stack, and CALL/RETURN for subroutines.

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Code: Peripherals

Code ch. 25 — getting data in and out: I/O ports vs memory-mapped I/O, polling vs interrupts, DMA, and device controllers.

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Code: The Operating System

Code ch. 26 — why raw hardware needs an OS: the kernel, system calls, processes and multitasking, memory management, file systems and drivers.

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Code: Coding

Code ch. 27 — from machine code to high-level languages: assemblers, compilers vs interpreters, high-level constructs, libraries and APIs.

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Code: The World Brain

Code ch. 28 — graphics, sound, networks, the internet and the web tying it all together, plus a look at where computing goes next.

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