LDA #$2 ; a=2 pc=0x602 c=0
ADC #$6 ; a=8 pc=0x604 c=0
SBC #$6 ; a=1 pc=0x606 c=1
-------------------------------------------------
- and b always 1
sp always 0x1ff
all the other values always 0
--------------------------------------------------
LDA #$2 ; a=2 pc=0x602 c=0
CLC ; a=2 pc=0x603 c=0
ADC ...

More time spent with the same tutorial you give as reference and more strange things appearing, i went to the debugger to try some simple math operations like these:

LDA #$15 ; a= 15
ADC #$7 ; a= 1c
SBC #$8 ; a= 13

then i did some little changes in the code trying to understand the thing ...

Thanks for all your kind and attention in the forum with me and my question.

The following code is the one who gave me the situation i reported initially, the program i'm using has the manual designed by Nick Morgan, you can find it online, searching for he's name, i'm following these manual ...

hi guys

i began recently studying 6502, i studied 8086, python, java and other programming languages, and now im curious about 6502, so i began following a tutorial who teached how to paint a pixel in the screen, using lda and sta commands, my question is sta takes the adress where the pixel will ...