int main(void) 
{
    unsigned char var1;
    while(1)
    {
         var1 = var1 | 0x10;         /* Set bit 4 (5th bit) of var1 */
         var1 = var1 & 0xEF;         /* Clear bit 4 (5th bit) of var1 */
    } 

    return 0;
}