` COMPUTE! ISSUE 54 / NOVEMBER 1984 / PAGE 100`

 PC Monochrome Graphics Michael A. Covington Here are some graphics screens which don't require a color/graphics adapter—they'll work on any IBM PC (or PCjr), even those equipped only with the monochrome display board. Owners of the IBM monochrome display often feel a bit left out because their systems do not support point-by-point graphics. The monochrome display adapter can produce a variety of special characters that could be used to construct drawings, but most programs never employ more than a few of them. The brief program accompanying this article takes advantage of these special characters to create dramatic-looking patterns—actually contour maps of three-dimensional mathematical functions. Some of the displays look rather like Scottish tartans. The program runs on a PC or PCjr with any display, but the IBM monochrome display yields the best results. Line 160 in the program defines the variable W as a function of ROW and COL. The function can be anything you wish. Here are some functions that result in attractive patterns: ```W = ROW + COL W = ROW*COL W = LOG(ROW)-LOG(COL) W = LOG(ROW2 + COL2) W = 5*SIN((ROW +COL/10) ``` An almost infinite variety of other functions are possible. Just substitute your function for line 160, save, and then run the program. Exit with Ctrl-Break. PC Monochrome Graphics Refer to "COMPUTEI's Guide For Typing In Programs" article before typing this program in. ```BP 30 SCRNWIDTH = 80 CE 50 DIM A\$( 4 ) KH 60 A\$ ( 0 ) = " " NM 70 A\$ ( 2 ) = CHR\$(176) NF 80 A\$ ( 2 ) = CHR\$(177) PO 90 A\$ ( 3 ) = CHR\$(178) HC 100 A\$ ( 4 ) = CHR\$(219) HI 110 CLS:KEY OFF CP 120 FOR R0W = 1 TO 22 JM 130 FOR COL = 1 TO SCRNWIDTH-1 NP 140 ' Change the following line EK 150 ' to get different patterns OH 160 W = SQRC ( (2*(R0W- 11))^2 + (COL-40)^2) AF 170 PRINT A\$ (ABS (W) MOD 5); ON 180 NEXT 190 PRINT 200 NEXT 210 BEEP ```