This compiles for the 12F683. May not be the correct pins to do the expected, I did not check that.
Code:
    ANSEL = %00000000
    CMCON0 = %00000111
    
    START: 
    'D0 HIGH
    GPIO = %11001111
    GPIO = %00010000
    PAUSE 500
    'D1 HIGH
    GPIO = %11001111
    GPIO = %00100000
    PAUSE 500
    'D2 HIGH
    GPIO = %11101011
    GPIO = %00010000
    PAUSE 500
    GOTO START
ANSEL is for turning the ADC on or off. Not clear why it gave an error.
The CMCON should have though.
"Overwriting previous address contents" is because I had the fuses set in code and the fuses commented out in the *.inc.
http://www.picbasic.co.uk/forum/showthread.php?t=543

Now for some data sheet reading