Add README

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+* Talks
+
+Slides and example code from two technical presentations given in 2020.
+
+Slides use [[https://orgmode.org/][org-mode,]] and were presented in Emacs with [[https://github.com/rlister/org-present][org-present]].
+
+** Concurrency (June 2020)
+
+Introduction to concurrency.
+
+*** Slides
+- Sequential vs. concurrent execution, I/O latency, interrupts, and cooperative vs. preemptive scheduling
+- Concurrency vs. parallelism, processes vs. threads, and language runtimes (C, JavaScript event loop, Go scheduler)
+- Shared memory synchronization vs. message passing, backpressure, and distributed data races
+
+*** Examples
+- temperatures: concurrent HTTP requests fetching city temperatures from OpenWeatherMap.
+- mutex: data race demonstration and mutual exclusion on a shared bank account balance (~go run -race ./main.go~).
+- csp: pipeline of goroutines and channels reading a CSV of zip codes, querying weather data with a concurrency limiter, and displaying a live top-ten leaderboard.
+
+To run the examples:
+#+begin_src shell
+# Mutex example (with and without race detector):
+cd concurrency/cmd/mutex
+go run ./main.go
+go run -race ./main.go
+
+# Weather examples (require an OpenWeatherMap API key):
+export OPEN_WEATHER_MAP_API_KEY="..."
+cd concurrency/cmd/temperatures && go run .
+cd concurrency/cmd/csp && go run .
+#+end_src
+
+** x86-64 Assembly (November 2020)
+
+A brief tour of x86-64 assembly on Linux.
+
+** Slides
+- Compilation pipeline, ISAs, CPU registers, and Linux system calls
+- Instructions, addressing modes, control flow, and memory safety
+- Virtual memory, the stack, function prologues/epilogues, and the System V AMD64 ABI calling convention
+
+** Examples
+- exit: minimal program invoking the ~exit~ system call.
+- math: basic arithmetic instructions (~mov~, ~add~, ~sub~, ~mul~, ~div~), inspected via exit status.
+- control-flow: loops, comparisons (~cmp~), and conditional/unconditional jumps (~je~, ~jmp~).
+- hello-world: writing a string from the ~.data~ section to stdout with the ~write~ system call.
+- safety: out-of-bounds memory overwrite across adjacent ~.data~ buffers.
+- stack: pushing bytes onto the stack and printing from ~%rsp~.
+- func: function call, stack frame setup (~%rbp~ / ~%rsp~), and return.
+
+To run the examples:
+#+begin_src shell
+as exit.s -o exit.o
+ld exit.o -o exit
+./exit
+echo $?
+#+end_src