Zeropage Addressing

zeropage_addressing.asm

; When Addressing Modes use 8-Bit in favour of 16-Bit encoded locations
; they are commonly called Zeropage addressing modes


; Example: Zeropage Indirect Indexed Addressing
; Fill the whole screen with Spaces.

     ldx #$04           ; load X-Register via Immediate Addressing 
     sta $fb           ; store into $fb via Zeropage Addressing
     lda #$04          ; load Accumulator via Immediate Addressing
     sta $fc           ; store into $fc via Zeropage Addressing
     lda #$20          ; load Y-Register Spacebar code via Immediate Addressing 

loop sta ($fb),y  ; store Accumulator value by Zeropage Indirect Indexed Addressing 
     iny          ; increase Y by implied Addressing
     bne loop     ; branch to loop until 255 locations have been addressed via Relative Addressing
     inc $fc      ; Increase most significant Byte to point to next page in Screen RAM
     dex          ; decrease X-Register by implied Addressing 
     bne loop     ; branch to Loop to continue filling the screen with Spaces via Relative Addressing
     rts          ; after four rounds we are done and return

Am I correct in assuming the chip registers are somehow reset to #$00 before the object code is run? Because your code seems to make this assumption. I was expecting, for instance, an lda #$00 before sta $fb on line 8.