williams-et-al-1983-apple-ii-computer-graphics

CHAPTER 6-TEXT AND LOW-RES 472 REM3 GR4 COLOR = 45 PLOT 2, 16 VLIN 11, 14 AT 217 COLOR = 128 HLIN 17, 19 AT 139 HLIN 24,26 AT 131 HLIN 16,2 AT 1411 HLIN 23,27 AT 1412 HLIN 15,27 AT 1513 COLOR = 1314 HLIN 15,26 AT 16150 HLIN 15,25 AT 1716 HLIN 14,25 AT 1817 COLOR = 918 HLIN 14,25 AT 1919 HLIN 14 ,25 AT 22 HLIN 14 ,26 AT 2121 COLOR = 122 HLIN 14 ,26 AT 2223 HLIN 14 ,27 AT 2324 HLIN 14 ,27 AT 2425 COLOR = 3 ·26 HLIN 15 ,26 AT 2527 HLIN 16,25 AT 2628 HLIN 16,25 AT 2729 COLOR = 63 HLIN 17,24 AT 2831 HLIN 17,24 AT 2932 HLIN 18, 19 AT 333 HLIN 22,23 AT 3Listing 6-2. Apple drawn using VLIN and HLIN.The PLOT was used for the top, VLIN for the remainder of the stem, andsince the colors in the apple run horizontally, HLIN was used fo r the restof the figure. Which of the commands you use most will depend solely onthe figure that you want to draw. This technique has obvious drawbacks ifthe picture is composed of many isolated blocks and few horizontal orvertical lines. In any event, it is quite tedious for the programmer; anaspect only partially balanced by the efficiency with which the program isexecuted.A variation on this technique is to place an HLIN statement within a loopand read the individual numbers from a data table as shown in Listing 6-3.1 GR2 COLOR = 4