Problem with Arduino Nano's serial Monitor ( Wrong character shown)

[twashin]

Unfortunately , didn't work

[camsysca]

@twashin

Unfortunately , didn't work

Well, I'm stumped. If that won't work on two different Nano's, with different cables, I suspect something is either wrong with your USB port, or your IDE install. Can you reinstall the IDE? No idea, by the way, why that would be the cause, but straws need grasping.
One other thing - do you have all warnings enabled for the compile and download process? Maybe you've got a warning suppressed that is relevant.
C
C

[twashin]

I tried with my laptop. But didn't work at all.

[UKHeliBob]

Try this

void setup()
{
  Serial.begin(9600);
  char text[] = {"ABCDEF"};
  Serial.println(text);
  for (int c = 0; c < strlen(text); c++)
  {
    Serial.print(byte(text[c]));
    Serial.print(" : ");
    Serial.println(text[c]);
  }
}

void loop()
{
}

[twashin]

Unfortunately , did not work.

[sterretje]

To eliminate serial montor as a possible cause, try another terminal program. For Linux e.g. minicom, for Windows e.g. realterm; no idea for Mac.

Make sure that serial monitor is closed when using the other terminal program. Make sure to close the other terminal program before uploading.

[ua6em]

microcontroller with overwritten marking 100500 WAVGAT)))
Try setting the monitor speed to 2400