Serial.read more than letter

Using Arduino Project Guidance
11

MostafaHamdy:
i try to make led high when enter 'on' in serial monitor and low when write 'off' i need to know why this code not operate

I suggest you buffer the incoming message in a null-terminated c-string, and use the standard string functions to manipulate it.

// incomplete, untested

void handleSerial()
{
    const int BUFF_SIZE = 32; // make it big enough to hold your longest command
    static char buffer[BUFF_SIZE+1]; // +1 allows space for the null terminator
    static int length = 0; // number of characters currently in the buffer

    if(Serial.available())
    {
        char c = Serial.read();
        if((c == '\r') || (c == '\n'))
        {
            // end-of-line received
            if(length > 0)
            {
                handleReceivedMessage(buffer);
            }
            length = 0;
        }
        else
        {
            if(length < BUFF_SIZE)
            {
                buffer[length++] = c; // append the received character to the array
                buffer[length] = 0; // append the null terminator
            }
            else
            {
                // buffer full - discard the received character
            }
        }
    }
}

void handleReceivedMessage(char *msg)
{
	if(strcmp(msg, "on") == 0)
	{
		// handle the command "on"
	}
	else
	{
		// etc
	}
}