BLUNO How To Switch Mode Programmatically

I know that you can issue
[code]
+++
AT+EXIT
[/code]

But, how do you do that from sketch?

According to your documentation, the Serial Monitor has to be switched to [b]newline[/b] only before it can enter the AT mode. But what if I don't even want to open the Serial Monitor and just enter the AT mode?
[code]
Serial.println("+++"); //this won't enter the AT mode.
[/code]

The full codes as below. I was trying to send SMS. And the GSM can only be initialised after I enter the AT mode, and exit the AT mode. Please assist.

[code]
/*
* Send SMS
* Written by Syahmul on 22/5/2014
* Memory consumed: 15Kb
* Need to active AT command first before it can work
* Ref: http://arduino.cc/en/Tutorial/GSMExamplesSendSMS
*/

// libraries
#include <GSM.h>

#define PINNUMBER ""

// initialize the library instance
GSM gsmAccess; // include a 'true' parameter for debug enabled
GSM_SMS sms;

void setup()
{
// initialize serial communications
Serial.begin(9600);

Serial.println("SMS Messages Sender");

// connection state
boolean notConnected = true;

// Start GSM shield
// If your SIM has PIN, pass it as a parameter of begin() in quotes
while(notConnected) {
Serial.println("+++"); //how to do this??
Serial.println(gsmAccess.begin());
if(gsmAccess.begin()==GSM_READY) {
notConnected = false;
}else {
Serial.println("Not connected");
delay(1000);
}
}
Serial.println("AT+EXIT\r\n"); //and this??
Serial.println("GSM initialized");
}

void loop()
{

Serial.print("Enter a mobile number: ");
char remoteNumber[20]; // telephone number to send sms
readSerial(remoteNumber);
Serial.println(remoteNumber);

// sms text
Serial.print("Now, enter SMS content: ");
char txtMsg[200];
readSerial(txtMsg);
Serial.println("SENDING");
Serial.println();
Serial.println("Message:");
Serial.println(txtMsg);

// send the message
sms.beginSMS(remoteNumber);
sms.print(txtMsg);
sms.endSMS();
Serial.println("\nCOMPLETE!\n");
}

/*
Read input serial
*/
int readSerial(char result[])
{
int i = 0;
while(1)
{
while (Serial.available() > 0)
{
char inChar = Serial.read();
if (inChar == '\n')
{
result[i] = '\0';
Serial.flush();
return 0;
}
if(inChar!='\r')
{
result[i] = inChar;
i++;
}
}
}
}

[/code]