In the first communication example - Reading a serial ASCII-encoded string.
the program looks for '/n' but does not find it.
The output of the following
Serial.println('/n'); // print as an ASCII-encoded decimal
Serial.println('/n', DEC); // print as an ASCII-encoded decimal
Serial.println('/n', HEX); // print as an ASCII-encoded hexadecimal
Serial.println('/n', OCT); // print as an ASCII-encoded octal
Serial.println('/n', BIN); // print as an ASCII-encoded binary

is
12142
12142
2F6E
27556
10111101101110
I do not see how any of these equate to Carriage Return which is ASCII 13 or LINEFEED which is 10

changeing the line
if (Serial.read() == '\n')
to
if (Serial.read() == 13)/)
and changing the drop down box at the bottom of the Monitor window to
Carriage return
then the program works

@gse76

yes this is a know problem with the Arduino IDE serial monitor.

@AlanTJohnstone

your problem is totally unrelated to the original issue, and it is probably better if you post such problems in the forum.

In any case you are confusing the escape sequence \n (with the backslash) with the two-characters sequence /n (with the normal slash).

'/n' is not an escape sequence but the concatenation of '/' and 'n' that are respectively 2F and 6E. This explains the numbers you're seeing (2F6E in various bases...), be sure to use '\n' instead.

You are quite correct of course. I typed in the wrong string when trying to understand the problem.
The fact remains that the code does not work no matter the setting at the bottom of Serial Monitor.

No line ending sends NO char (as you would expect)
Newline sends 10 only (as you would expect)
Carriage return sends 13 only (as you would expect)
NL and CR sends 13 only (as you would NOT expect)

I do not know what ‘\n’ is interpreted as in the “ if ” statement but replacing it with “ int(‘\n’) ”
is equivalent to 10 so works with the Newline setting above

Alan

I apologize if I should not be bothering you. If you could tell me where I should address these thoughts I will do so.

I have done more experimenting with the problem and converting the Serial.read() to a char by

char test=(char)Serial.read();
if(test=’\n’)......

does NOT work with “ Both NL and CR”

but it DOES work in the Serial Event example

There are two things that are different between the two instances
1 The if statement is in the serialEvent() function which does not seem a likely cause.

2 In the first program the test follows Serial.parseInt()

Can you mix the two forms of working?

Alan

@AlanTJohnstone
Please open a discussion for this issue on the forum in the "Suggestions for the Arduino Project" subsection.
Post a link to that discussion here and when the forum reaches a solution it can be posted here again. That way we can help the Arduino core team to improve the core code.
Thanks,

@gse76, as @cmaglie said, this is a know limitation of Serial Monitor, unlikely to be fixed. Serial Monitor is not a terminal and it's unable to properly handle a handful of control codes. Please use tools like putty or cutecom instead
@AlanTJohnstone please open a specific issue with your request, if your enquiry is still valid

It's also cannot recognized on Linux screen serial monitor
screen /dev/ttyUSB0

Duplicate of #346