Clearing and changing the text on LCD display

Hi everyone,
I hate to ask such a basic question, but I am learning and hope I have this question in the right place.
I have wired up my arduino uno to the standard LCD display supplied in the starter kit and have the display successfully reading " hello, world!" I would like to change the text, but when I try and do this I get an error message saying"

Arduino: 1.7.7 (Mac OS X), Board: "Arduino Uno"

Sketch uses 2,328 bytes (7%) of program storage space. Maximum is 32,256 bytes.
Global variables use 55 bytes (2%) of dynamic memory, leaving 1,993 bytes for local variables. Maximum is 2,048 bytes.
avrdude: ser_open(): can't open device "/dev/tty.usbmodemfa131": No such file or directory
ioctl("TIOCMGET"): Inappropriate ioctl for device
Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

This report would have more information with
"Show verbose output during compilation"
enabled in File > Preferences.

I am guessing it is because I need to clear the text before trying to re-write? but I can't find how to clear the text and any examples I copy and paste from forums do not work. I have spent over an hour trying to figure this out so please don't think I am being lazy!

This is the original code I was using, I wanted to change the text to read something else within the 16 character boundary.

I appreciate any help!

/*
  LiquidCrystal Library - Hello World

 Demonstrates the use a 16x2 LCD display.  The LiquidCrystal
 library works with all LCD displays that are compatible with the
 Hitachi HD44780 driver. There are many of them out there, and you
 can usually tell them by the 16-pin interface.

 This sketch prints "Hello World!" to the LCD
 and shows the time.

  The circuit:
 * LCD RS pin to digital pin 12
 * LCD Enable pin to digital pin 11
 * LCD D4 pin to digital pin 5
 * LCD D5 pin to digital pin 4
 * LCD D6 pin to digital pin 3
 * LCD D7 pin to digital pin 2
 * LCD R/W pin to ground
 * LCD VSS pin to ground
 * LCD VCC pin to 5V
 * 10K resistor:
 * ends to +5V and ground
 * wiper to LCD VO pin (pin 3)

 Library originally added 18 Apr 2008
 by David A. Mellis
 library modified 5 Jul 2009
 by Limor Fried (http://www.ladyada.net)
 example added 9 Jul 2009
 by Tom Igoe
 modified 22 Nov 2010
 by Tom Igoe

 This example code is in the public domain.

 http://www.arduino.cc/en/Tutorial/LiquidCrystal
 */

// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  // Print a message to the LCD.
  lcd.print("hello, world!");
}

void loop() {
  // set the cursor to column 0, line 1
  // (note: line 1 is the second row, since counting begins with 0):
  lcd.setCursor(0, 1);
  // print the number of seconds since reset:
  lcd.print(millis() / 1000);
}

It looks to me as though your computer doesn't see your device.

"avrdude: ser_open(): can't open device "/dev/tty.usbmodemfa131": No such file or directory"

Have you tried to disconnect and reconnect your arduino from the computer?
If you already did, it is possible that your device designation has changed and the device is no longer "/dev/tty.usbmodemfa131". I don't own a MAC so I can't verify the latter.

regards

I am guessing it is because I need to clear the text before trying to re-write?

Once you get your Arduino <–> MAC communication problem fixed you will find that there is no need to clear the LCD text before trying to re-write.

In fact the process of ‘clearing’ the screen is nothing more than writing spaces where the characters used to exist.

Don

alexhigby:
Arduino: 1.7.7 (Mac OS X), Board: "Arduino Uno"

That's not an official version of Arduino. You shouldn't be getting anything from Arduino.org. Go to Arduino.cc and download official version. The latest one is 1.6.6 Those posers give their stuff higher numbers to try to get people to download their instead of the official one.

Delta_G thank you very much, that fixed the problem straight away.
and thank you everyone else for your help.