Apple IIe - Page 237

Apple lie Graphics 237
Table 6-3. Vectors
vector#
direction binary code
1
I move 010
2 I move 010
3
- plot
101
4
- plot
101
5 1 plot 100
6
1 plot
100
7 1
plot
100
8
1
plot
100
9
-
plot
111
10
-
plot
111
11
-
plot
111
12
-
plot
111
13 I
plot
110
14 I
plot 110
15 I
plot
110
16 I
plot 110
17
-
plot
101
18
- plot
101
The Apple lie stores information in words of eight bit binary
numbers. Because the binary direction codes are only three bits
long, it would be wasteful to put only one plotting vector in a
memory location. Usually two and sometimes three plotting
vectors can be stored in a specific memory address.
A
few rules must be followed while packing the binary codes
into memory:
1- all bytes are read from right to left.
2- if all remaining sections of a byte contain all zeros
the rest of the byte will be ignored.
3- only a move instruction may be placed in section X
of a byte.