Graphics 15 to IBM CGA Converter¢--------------------------------¢¢ First a little background info. I first used a PC computer a couple of years ago on an Employment training course, and after the usual standard training in spreadsheets, word processing and database's, I started to play around with the different screen modes via GWbasic.¢ Screen 1 is a CGA (Color Graphics Adaptor) mode with 320 by 200 scanlines and is interlaced. The total number of bytes for a screen is 16,384 ($4000) and the number of bytes per scanline is 80 ($50). If we count from 0 to 199 as a computer would, the data for the even numbered scanlines (0,2,4,6 etc), is stored consecutiveley from the beginning of the picture data (7 byte header in the file). The data for the odd numbered scanlines (1,3,5,7 etc), starts at an offset of 8192 ($2000) bytes from the beginning.¢ What I wanted to do was convert a demo over from the Atari to the PC, and to aid me I wrote a program to take a 62 sector binary saved screen and convert it automatically to a BSAVE format that the PC would recognise. There's nothing brilliant about it, what it does is expands the screen data horizontally from 160 pixels to 320 pixels. The vertical resolution is left intact (192) and filler bytes are included to make up the difference.¢ As BASIC is not my forte, feel free to modify the program.¢ After the picture has been converted you need some kind soul with an ST and a program called XFORMER, to convert the file over to a 3.5" disk.¢ If anyone is interested enough, for a blank 3.5 or 5.25 disk and return postage, I can send some pictures that have already been converted and ported over, plus a machine code fade routine and demo converted from THE best computer. I can be contacted at the address below.¢¢¢Ken Hill,¢35 Somerset Road,¢Hateley Heath,¢West Bromwich,¢West Midlands.¢B71 1HW.¢
