Here is the sample HiTECH C program I cannot get to work on the PIC16F877

What am I doing wrong?
Thanks
Pete

#include <pic.h>

typedef unsigned char UINT8;
typedef unsigned short UINT16;

#define TIMER_PRESET    50

/***************************************************************************
***
 *                              Subroutines
;***************************************************************************
***/
/*-----------------------------
initalisation --------------------------------*/
void    init_pic(void)
    {
    // Configure TMR0 Port and interrupts

    TRISC = 0x0;

    T0CS = 0;       // Timer increments on instruction clock
    T0IE = 1;       // Enable interrupt on TMR0 overflow
    INTEDG = 1;     // Rising edge trigger the interrupt
    INTE = 1;       // enable the external interrupt RB0 change
    GIE = 1;        // Global interrupt enable
    }

/***************************************************************************
***
 *                        Interrupt Service Routine

****************************************************************************
*/
static void interrupt
isr(void)
{
/*-------------------------- TMR0 timer
interrupt ---------------------------*/
    if (T0IF) {
        TMR0 = TIMER_PRESET;
        T0IF = 0;          // clear the interrupt flag

    }
}
/* ****************************** END ISR
************************************/

void main(void)
{
    UINT8 counter=0;
    UINT16 counter1=0;
    init_pic();

background_tasks:

    if ( counter1 == 0)
    {
        PORTC = counter;
        counter++;
    }
    counter1++;

    goto    background_tasks;
}

/////////////////////////////  END OF FILE
////////////////////////////////////

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