As I said the bsc-1.0/ebin is empty and don't easy for new beginner to run through .

In section "Wrapping Up" of chapter 11:

In doing so, the user’s guide introduces the target_system.erl module shipped in the sasl application’s examples directory as well as in this chapter’s directory in the book’s GitHub repository.

Does it mean this repository included "target_system.erl" module in ch11 directory? But I didn't find it.

Thanks.

there is no terminate implement.

frequency:deallocate does not care what the allocatable frequencies are and happily inserts non-allocatable frequencies in the "allocatable" list, even duplicating them.

Erlang/OTP 18 [erts-7.3] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false]

Eshell V7.3  (abort with ^G)
1> c(frequency).
frequency.erl:4: Warning: undefined callback function code_change/3 (behaviour 'gen_server')
{ok,frequency}
2> frequency:start().
{ok,<0.41.0>}
3> l(sys).
{module,sys}
4> sys:statistics(frequency, true).
ok
5> sys:get_state(frequency).
{[10,11,12,13,14,15],[]}
6> frequency:deallocate(999).
ok
7> sys:get_state(frequency). 
{[999,10,11,12,13,14,15],[]}
8> frequency:deallocate(10). 
ok
9> sys:get_state(frequency).
{[10,999,10,11,12,13,14,15],[]}

Starting at page 193 (Chapter 8: Gluing it all together) phone:start_test/2 needs to work differently than the way it is currently represented in this repository. phone:start_test(150, 500) uses

start_test(Num, Calls) ->
    [phone_fsm:start_link(X) || X <- lists:seq(1,Num)],
    call(Calls, Num).

which means that the phone_fsm processes are not running under the supervision of the simple_phone_sup (or phone_sup) supervisor. One possible workaround could be to define phone:start_test/3 such that:

start_test(Attach, Num, Calls) ->
    [Attach(X) || X <- lists:seq(1,Num)],
    call(Calls, Num).

Then it could be used as:

• phone:start_test(fun phone_fsm:start_link/1 ,150, 500).
• phone:start_test(fun simple_phone_sup:attach_phone/1 ,150, 500).
• phone:start_test(fun phone_sup:attach_phone/1 ,150, 500).