LACE CURTAIN
By Fred Cornett
CURSOR 1, no. 3 (March 1980): 21.


Screen Format Output Ports

If you wish to put more than 2 colors onscreen simultaneously (while using TINY 
BASIC) without resorting to machine language, it can only be done by formatting 
the screen. Port "&(9)" is the "Horizontal Blanking Register." By setting this 
port to various values, it will do a number of things:

1. Vertically split the screen
2. Put up screen borders

Input this program example:

10 FOR A=0TO 256;&(9)=A;PRINT A;NEXT A

The Color Ports are as follows:

Ports &(0) through &(3) control the colors used on the Right side of the screen 
(in conjunction with the use of &(9)).

Ports &(4) through &(7) control the colors used on the Left side of the Screen 
(in conjunction with the use of &(9)).

To use these ports, you assign them values just as you assign values to FC or 
BC.

Look at lines 5 and 6 of the following program, and you will see how to assign 
value to these ports.

NOTE: "&(10)" is the "Vertical Blanking Register." Substitute &(10) for &(9) in 
the above one line program to see how it works


Lace Curtain

5 BC=10;FC=83
6 &(2)=0;&(1)=53;&(0)=53
10 CLEAR ;&(9)=148;FOR A=-79TO 79STEP 2;BOX A,0,1,87,1;NEXT A
20 FOR A=43TO -43STEP -2;BOX 0,A,159,1,1;NEXT A;FOR A=1TO 100;BOX 0,0,RND 
(159),RND (87),3;NEXT A;RUN

The preceding program puts up 4 colors at the same time. By changing the value 
of &(, you will get 5 colors. Try experimenting!
