Eleven Plates from bits to browsers

Four pages to begin. Unary, then binary: one byte is eight bits, the place values run 128 down to 1, and the lecture spells 01000001, with “bit” and “Byte” written over the stills in yellow. Then ASCII (65 is A, 97 is a), the three lines of a phone-book search and its thirteen lines of pseudocode, and 72, 73, 33 in red, green and blue boxes.

The notebook first repeats Week 0’s four pages; C begins on page 5, with source code, machine code and make hello. His own agree.c goes from a buggy first try to “Agreed.”, an if / else-if is drawn as a flowchart by hand, a doubling dollar overflows its integer, and on page 23 his mario.c prints a four-row staircase, flush left. CS50’s shorts fill the rest: types, operators, Boolean logic, loops, the Linux command line and magic numbers.

Compiling in four steps, an off-by-one in his row.c caught in the debugger, and int scores[3] holding 72, 73 and 33. Then HI! laid out in memory, the Caesar cipher (HI! becomes IJ!, and UIJT XBT DT50 decodes back), argc and argv, and two full pages of colour handwriting: the anatomy of a function, and local against global scope.

Searching behind doors, linear and binary, beside a chart of growth from O(1) to O(n!). A phone book built from a typedef’d struct, the lecture’s race between selection, merge and bubble sort, and recursion unwinding f(4) down to 24. The shorts add the bounds: O(n²) and Ω(n²) for selection sort, O(n log n) for merge sort, and Collatz for good measure.

The longest notebook. It opens on pixel art and hexadecimal colour, then addresses: int *p = &n printing real ones, a lecture still with “0x123, Stored, Pointer” written over it, pointer arithmetic on HI!, and, on pages 11 and 12, compare.c, where s and t point at two separate HI! strings at 0x123 and 0x456. Then malloc and free, Valgrind, garbage values, swap and file I/O, with shorts on the heap, the stack and file pointers.

A linked list built node by node until list → 3 → 2 → 1, a hash table of Nintendo characters, and a trie that spells TOADETTE. The section adds a “Hey!” → “Hi!” list and what makes a good hash function; the shorts cover structs and the arrow operator, singly and doubly linked lists, stacks, queues, hash tables with probing and chaining, and tries.

clang -o hello beside python hello.py, and his own Codespace, where hello.py says hello after two rounds of “command not found”. Then C and Python side by side: if and else, get_string and input, strcmp and ==, lists, string methods, range, dictionaries and csv.DictReader, with shorts on tuples, comprehensions, functions and a Student class.

The class’s favourite languages go from a Google Form to a CSV to Python, then into SQL: CREATE TABLE, sqlite3, SELECT DISTINCT language (Python, C, Scratch) and COUNT(DISTINCT language), which says 3. Then the clauses, INSERT and DELETE, and a page of data types.

The internet first: an early network map, routers, TCP/IP, HTTP against HTTPS, and status codes down to 418, I’m a Teapot. Then HTML and its DOM tree, his own list.html and video.html in the browser, regular expressions in form patterns, CSS selectors, and JavaScript beside Scratch with every event a page can hear. Shorts on DNS, DHCP, ports and DOM methods close it.

Two pages. A raw request, GET /search?q=cats, and a whole Flask application: one route, /, returning “hello, world”. The second page lists a Flask project’s bones: app.py, requirements.txt, static/ and templates/.

Not a recap but a list of beginnings: where to host a website and a web app, where to ask questions and read the news, and the syllabi of CS50’s next courses, in Python, R, the web, AI, SQL and cybersecurity.