Commodore 64 Uživatelský manuál stáhnout pdf (Strana 29)

As a further example, you can modify the sine curve program to dis-

playa semicircle. Here are the lines to type to make the changes:

50 FORX=0T0160:REM DO HALF THE SCREEN

55 'T' 1 '" 1 iZII21+SC!F: ( 161?!,jo::x:-:;<::t.;:.::)

56 Y2=100-SQR(160:t.X-X*X)

60 FORY=Y1TOY2STEPY1-Y2

7121 CH= nn (:x:/:::)

80 RO=U-ITCT'/8)

85 .U'I='T'AND7

90 BY=BASE+RO*320+S:t.CH+LN

10tC1 E:I=7-C<:At'1Dn

1 H3 POKEB'T'., PEEK (B'T') OR (2 'T'BI )

114 ~IEXT

This will create a semicircle in the

HI-RES area of the screen.

WARNING: BASIC variables can overlay your high-resolutionscreen. If you need

more memory space you must move thebottomof BASIC above the high-resolution

screen area. Or, you must move your high-resolutionscreen area. This problem will

NOT occur in machine language. ItONLY happens when you're writing programs

BASIC.

MULTI-COLORBIT MAP MODE

Like multi-color mode characters, multi-color bit map mode allows you

to display up to four different colors in each 8 by 8 section of bit map.

And as in multi-character mode, there is a sacrifice of horizontal resolu-

tion (from 320 dots to 160 dots).

Multi-color bit map mode uses an 8K section of memory for the bit

map. You select your colors for multi-color bit map mode from (1) the

background color register 0, (the screen background color), (2) the video

matrix (the upper 4 bits give one possible color, the lower 4 bits an-

other), and (3) color memory.

Multi-color bit mapped mode is turned ON by setting bit 5 of 53265

($D011) and bit 4 at location 53270 ($D016) to a 1. The following POKE

does this:

POKE 53265,PEEK(53625)OR 32: POKE 53270,PEEK(53270)OR 16

PROGRAMMING GRAPHICS 127

1 2 ... 24 25 26 27 28 29 30 31 32 33 34 ... 82 83

Žádné komentáře

Commodore 64 Uživatelský manuál Strana 29