semaphores
Visual signaling system
Semaphores are systems for signaling across distance.
The original semaphore used movable arms on a post, with different positions representing letters or messages—a precursor to the telegraph.
Flag semaphore uses handheld flags in the same way.
In computing, a semaphore is a variable that controls access to shared resources, preventing conflicts when multiple processes try to use something simultaneously: The program uses semaphores to manage concurrent threads.
flags
Symbolic national cloths
telegraphy · alphabet · arm · position · movement · tower · station · signalman · encode · decode
thread
Fiber for stitching
- lockMechanism requiring a key
- synchronizationAligning timing across systems
- processSteps toward a result
concurrency · resource · blocking · wait · signal · counter · binary · counting · deadlock · access
- railroadstrains, train, tracks, track, locomotive
- model trainsmodel trains, train set, train sets, electric trains, electric train
- Unixbash, cat, cd, grep, chmod
- rail yardsswitchyard, marshalling yards, receiving yard, yard crew, yardmaster
- railroadianarailroad spikes, railroad maps, rail passes, waybills, ticket stubs
- system APIsfile system, memory management, permissions, pipes, shared memory
semaphoresverbal communication
Exchange through spoken language
speech · radio · spoken language · telephone · conversation
semaphoresradio
Electromagnetic wave receiver
wireless transmission · radio signals · electronic communication · telegraph · telephone
semaphoreslock
Mechanism requiring a key
barrier · monitor · race condition · deadlock