Serial.write() command doesn’t format the bytes as ASCII characters.
void setup() {
// start serial port at 9600 bps:
Serial.begin(9600);
}
void loop() {
// read analog input, map it to make the range 0-255:
int analogValue = analogRead(A0);
int mappedValue = map(analogValue, 0, 1023, 0, 255);
Serial.println(mappedValue);
// print different formats:
Serial.write(mappedValue); // Print the raw binary value
Serial.print('\\t'); // print a tab
// print ASCII-encoded values:
Serial.print(mappedValue, BIN); // print ASCII-encoded binary value
Serial.print('\\t'); // print a tab
Serial.print(mappedValue); // print decimal value
Serial.print('\\t'); // print a tab
Serial.print(mappedValue, HEX); // print hexadecimal value
Serial.print('\\t'); // print a tab
Serial.print(mappedValue, OCT); // print octal value
Serial.println(); // print linefeed and carriage return
}

[ ] Why:
[ ] 1.7.0 doesn’t matter


serial.write() function is versatile. If you give it a variable or literal that’s a numeric data type, it will send it as its raw binary value.