3x4 keypad scanning

I Found this site:
http://www.massmind.org/techref/microchip/3x4Key-4bLCD-Lock.htm

is this the part of scanning??

BSF PORTA,0 ;Poke column 1 high
CALL DETERMINE ;Check PORTB lower nibble for change
BCF PORTA,0 ;Clear column 1
BSF PORTA,1 ;Poke column 2 high
CALL DETERMINE ;Check PORTB lower nibble for change
BCF PORTA,1 ;Clear column 2
BSF PORTA,2 ;Poke column 3 high
CALL DETERMINE ;Check PORTB lower nibble for change
BCF PORTA,2 ;Clear column 3
GOTO TESTDATA ;Loop, check everything again