> Now, does this mean that when I hit the button attached to RA3, the pic 
> should jump right to mem-location 0x04 and from there run my Interrupt 
> Service Routine?

Is the button changing the level on RA3 ? IOW, is the button connecting
RA3 to Vdd or, what is implied next, grounding a pull-up ?

The /RAPU bit is cleared, which enables internal RA pull-ups

 ; Set prescaler to devide clock by 256
 MOVLW 0x07
 MOVWF OPTION_REG

         movlw   b'00000111'
;                  0           enable RA pull-ups
;                       111    PS2,1,0 TMR0 pre-scaler = 256
         movwf   option_reg

You could also use Boolean bit-setting by name

I still suggest you use BANKSEL to change bank

eg

BANKSEL CMCON0
CLRF CMCON0            ; Clear CMCON0

The instruction obviously does clear CMCON0. A more useful
comment would explain why it is cleared

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