EK-TM4C123GXL: What should be the reason for not able to see data using UART1 with PC4 and PC5 pins?

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

int
main(void)
{
    //
    // Set the clocking to run directly from the external crystal/oscillator.
    // TODO: The SYSCTL_XTAL_ value must be changed to match the value of the
    // crystal on your board.
    //


    SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN |
                   SYSCTL_XTAL_16MHZ);
    //
    // Enable Peripheral Clocks 
    //
    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_UART1);
    MAP_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOC);

    //
    // Enable pin PC5 for UART1 U1TX
    //
    MAP_GPIOPinConfigure(GPIO_PC5_U1TX);
    MAP_GPIOPinTypeUART(GPIO_PORTC_BASE, GPIO_PIN_5);

    //
    // Enable pin PC4 for UART1 U1RX
    //
    MAP_GPIOPinConfigure(GPIO_PC4_U1RX);
    MAP_GPIOPinTypeUART(GPIO_PORTC_BASE, GPIO_PIN_4);

    //
    // Configure the UART for 115,200, 8-N-1 operation.
    // This function uses SysCtlClockGet() or ui32SysClock to get the system clock
    // frequency.  This could be also be a variable or hard coded value
    // instead of a function call.
    //

    UARTConfigSetExpClk(UART1_BASE, SysCtlClockGet(), 115200,
                        (UART_CONFIG_WLEN_8 | UART_CONFIG_STOP_ONE |
                         UART_CONFIG_PAR_NONE));

    //
    // Put a character to show start of example.  This will display on the
    // terminal.
    //
    UARTCharPut(UART1_BASE, '@');


    //
    // Return no errors
    //
   return(0);
}