Commodore 64 User Manual page 73

priate screen memory location, that character will be displayed in the
proper position.
0 10
COLUMN
20
30
39
1063
1024 -
1064
1104
1144
1184
1224
1264
1304
1344
1384
1424
1464
1504
1544
1584
1624
1664
1704
1744
1784
1824
1864
1904
1944
1984
0
20
24
f
2023
Screen memory in the Commodore 64 normally begins at memory
location 1024, and ends at location 2023. Location 1024 is the upper left
corner of the screen. Location 1025 is the position of the next character
to the right of that, and so on down the row. Location 1063 is the
right-most position of the first row. The next location following the last
character on a row is the first character on the next row down.
Now, let's say that you're controlling a ball bouncing on the screen.
The ball is in the middle of the screen, column 20, row 12. The formula
for calculation of the memory location on the screen is:
POINT = 1024 + X + 40*Y
COLUMN
ROW
where X is the column and Y is the row.
Therefore, the memory location of the ball is:
1024 + 20 + 480 or 1524
COLUMN
ROW (40' 12)
63