Glossary

Quick-reference for terms used across the vault. Each links to the relevant note.

CS and Algorithms

Big O — asymptotic upper bound on growth. See Big O Notation.
Cache locality — accessing memory in patterns that hit CPU cache. See Arrays.
Hash collision — two keys mapping to the same bucket. See Hash Tables.
Recursion — function calling itself with a smaller subproblem. See Recursion.
Memoization — caching results of expensive function calls. See Dynamic Programming.

System call — interface between user space and kernel. See System Calls.
Virtual memory — abstraction giving each process its own address space. See Memory Management.
File descriptor — integer handle to an open file/socket. See File IO in C.
Context switch — saving/restoring CPU state between processes. See Scheduling.
Deadlock — circular wait on locks. See Concurrency and Synchronization.
Pointer — variable holding a memory address. See Pointers and Memory.
Segfault — accessing memory you don’t own. See Debugging with GDB.

Socket — endpoint for network communication. See Socket Programming.
Three-way handshake — TCP connection setup (SYN, SYN-ACK, ACK). See TCP Protocol.
Subnet — logical partition of an IP network. See IP and Routing.
TLS — transport layer security, encrypts TCP streams. See TLS and Encryption.

GPIO — general-purpose input/output pin. See GPIO and Digital IO.
ISR — interrupt service routine. See Interrupts and Timers.
PWM — pulse width modulation, simulates analog via duty cycle. See Motors and Actuators.
ADC — analog-to-digital converter. See ADC and DAC.
RTOS — real-time operating system with deterministic scheduling. See RTOS Fundamentals.
Volatile — C keyword preventing compiler optimization of memory reads. See Memory-Mapped IO.
MOSFET — metal-oxide-semiconductor FET, used as switch/amplifier. See Transistors as Switches.
Op-amp — operational amplifier, high-gain differential amp. See Op Amps.
Decoupling cap — capacitor placed near IC power pins to filter noise. See Power Supply Design.
Impedance — AC resistance (magnitude + phase). See Signal Integrity.

PID — proportional-integral-derivative controller. See PID Controller.
Kalman filter — optimal estimator for linear systems with Gaussian noise. See Kalman Filter.
Transfer function — Laplace-domain ratio of output to input. See Transfer Functions.
Sensor fusion — combining multiple sensors for better estimates. See Sensor Fusion.
Kinematics — geometry of motion without forces. See Kinematics.
SLAM — simultaneous localization and mapping. See SLAM.