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+options :
+```
+- n_phi -> number_of_philosophers
+- t_die -> time_to_die
+- t_eat -> time_to_eat
+- t_slp -> time_to_sleep
+- n_eat -> [number_of_times_each_philosopher_must_eat]
+```
+
+**thread :**
+
+- parts of a process that performs code simultaneously
+- thread are light-weight-process (LWP) that happens inside a process (observe with command `ps -eLf`)
+- a process can be single-threaded or multi-threaded
+- different process have a different PID and different LWP, different thread in the same process have the same PID and different LWP
+- thread vs process :
+
+  *process :*
+
+  - process is isolated, it doesn't share memory with any other process
+  - process is less efficient in communication, it takes more times to create or terminate or switch
+  - process speed is not impacted by speed of other process (untill it reach the limit of cpu)
+
+  *thread :*
+
+  - thread are not isolated, they share memory with the other threads
+  - thread is more efficient in communication, it takes less times to create or terminate or switch
+  - thread can become slow if the process does many concurrent tasks
+
+- ressources :
+  - https://www.baeldung.com/linux/process-vs-thread
+
+**mutex :**
+
+- mutual exclusion
+- to prevent a part of the code to be performed simultaneously by threads
+- the section of code wraped by a mutex can be access by only one thread at a time
+- the section starts by unlocking a mutex, and end by locking it
+
+**external function :**
+
+- `memset`      : fill memory with a constant byte
+- `printf`      : format and print data
+- `malloc`      : allocate dynamic memory
+- `free`        : free dynamic memory
+- `write`       : write to a file descriptor
+- `usleep`      : suspend execution for microseconds intervals
+- `gettimeofday`: get time
+- `pthread_create`       : create a new thread
+- `pthread_join`         : wait for a thread to finish, 
+- `pthread_detach`       : when a thread is detached it cannot be join, you cannot wait for it to teminate, it will release its ressources on its own when it has finish
+- `pthread_mutex_init`   : initialize a mutex
+- `pthread_mutex_destroy`: destroy a mutex
+- `pthread_mutex_unlock` : unlock a mutex
+- `pthread_mutex_lock`   : lock a mutex
+
diff --git a/philosopher.pdf b/philosopher.pdf
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