.\Project1.axf: Error: L6218E: Undefined symbol main (referred from rtentry2.o).

hey i am new to keil i am getting this error

.\Project1.axf: Error: L6218E: Undefined symbol main (referred from rtentry2.o).
Not enough information to list image symbols.
Finished: 1 information, 0 warning and 1 error messages.
".\Project1.axf" - 1 Error(s), 0 Warning(s).
Target not created

please help below i have posted the code.
//*****************************************************************************
// Copyright (c) 2014 Texas Instruments Incorporated. All rights reserved.
// Software License Agreement
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the
// distribution.
//
// Neither the name of Texas Instruments Incorporated nor the names of
// its contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// This file was automatically generated by the Tiva C Series PinMux Utility
// Version: 1.0.4
//
//*****************************************************************************

#include <stdint.h>
#include <stdbool.h>
#include "assignment.h"
#include "inc/hw_types.h"
#include "inc/hw_memmap.h"
#include "inc/hw_gpio.h"
#include "driverlib/sysctl.h"
#include "driverlib/pin_map.h"
#include "driverlib/rom_map.h"
#include "driverlib/gpio.h"

//*****************************************************************************
void
PortFunctionInit(void)
{ // // Enable Peripheral Clocks // MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);

// // Enable pin PF2 for GPIOOutput // MAP_GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_2);

// // Enable pin PF0 for GPIOInput //

// //First open the lock and select the bits we want to modify in the GPIO commit register. // HWREG(GPIO_PORTF_BASE + GPIO_O_LOCK) = GPIO_LOCK_KEY; HWREG(GPIO_PORTF_BASE + GPIO_O_CR) = 0x1;

// //Now modify the configuration of the pins that we unlocked. // MAP_GPIOPinTypeGPIOInput(GPIO_PORTF_BASE, GPIO_PIN_0);

// // Enable pin PF4 for GPIOInput // MAP_GPIOPinTypeGPIOInput(GPIO_PORTF_BASE, GPIO_PIN_4);

// // Enable pin PF3 for GPIOOutput // MAP_GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_3);
}