When several processes run concurrently and share the same resource, the code that touches that resource must be protected. That protected code is called the critical section.
How this simulation maps to the theory:
• The app cards (Amazon, Netflix, Spotify, Chrome, Slack) are concurrent processes.
• The red booth is the critical section.
• The screen inside the booth is the shared resource — a file, a printer, a database row, or a block of memory.
• The booth door is the lock (a mutex or binary semaphore).
• Walking up and requesting the booth is the entry section; leaving and unlocking the door is the exit section; wandering around outside is the remainder section.
Why it matters: if two processes wrote to the shared screen at the same instant, the final value would depend on who happened to finish last. That bug is called a race condition, and it produces corrupted data that is very hard to reproduce.
Any correct solution must satisfy three requirements:
1. Mutual Exclusion. If one process is executing inside its critical section, no other process may be inside its own critical section at the same time. Here: only one app fits in the booth, and the door locks behind it.
2. Progress. If no process is in the critical section and one or more processes want to enter, only those processes that are actually contending may take part in deciding who goes next, and that decision cannot be postponed indefinitely. Here: when the booth is free, a waiting app is admitted straight away — an idle app that is not asking cannot block it.
3. Bounded Waiting. After a process requests entry, there must be a limit on how many times other processes are allowed in before its own request is granted. Here: the queue is served in order, so no app waits forever. Without this, a process could starve.
Note that the booth being busy blocks a process — it does not corrupt it. Being made to wait is the intended, correct behaviour. Deadlock is a different problem, which occurs only when processes hold one resource while waiting for another.