docs: demo description

README.md

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-# inter
-
-Simple inter-process communication demo

docs/PROJECT.md

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+## Inter-process communication between two processes
+
+### System overview
+
+| Process     | Description                                                                                       |
+| ----------- | ------------------------------------------------------------------------------------------------- |
+| `init`      | Forks 4 child processes, reads data from them, and writes that data to the shared memory          |
+| `P1-P4`     | Generates random priority number (in the range 0-19) and sends that priority number to the parent |
+| `scheduler` | Creates the shared memory segment, reads data written into it, and prints that data               |
+
+![Project system overview](./media/system-overview.png)
+
+### Implementation criteria
+
+**Criteria 1:**
+
+- Init is a parent process, which forks child processes P1-P4 (`fork` syscall)
+- P1-P4: Process should generate a random integer number between 0-19 (random number generation or simply hardcoded)
+- P1-P4 should send the random number to init through message passing (`pipe` syscall)
+- Init should read data sent by P1-P4
+
+**Criteria 2:**
+
+- Scheduler is an independent process: it should create a shared memory segmnet (`shmget` and related syscalls)
+- Scheduler should read dadta (a list of random numbers) written by init, sort the list in ascending order, and print the list (sorting algorithm of choice)
+
+**Criteria 3:**
+
+- Init should attach to the shared memory created by the scheduler process (`shmat` and related syscalls, hardcoded to any unique key of choice -> `ftok` syscall is a clean way to accomplish this)
+- Init should write random numbers from P1-P4 into the shared memory
+
+**Termination:**
+
+- After scheduler prints the data, init should detach from shared memory and scheduler should detach and delete the shared memory segment (`schmdt` and `shmctl` syscalls)