PAGE 6 "THE INFORMER" BY MATT LOVELESS & MIKE EGGERS(From the May '86 Antic) (synopsis) The Informer puts a four-item status line into thescreen display of your BASIC programs. This finalinstallment of the Page 6 Grab-Bag is a BASIC program thatworks on all 8-bit Atari computers of any memory size, withdisk drive. The third and final installment of our Page 6 Grab-Bagseries is a single program, The Informer, that creates asingle-line "text window" in your 8-bit Atari and lets yousee the current [SHIFT]-[CAPS] mode, the cursor row andcolumn, and the amount of free memory left for your BASICprogram. (Page 6 is 256 memory bytes from location 1536 to 1791-- $0600 $06FF in hexadecimal. "Protected" from theoperating system and BASIC, Page 6 provides a safe homebasefor fast, powerful machine language routines which can becalled from your BASIC program. The Informer places a status line above your standardscreen display. The information there is updated sixty timesper second. From left to right, the line provides thefollowing information: MODE indicates the current [CAPS]-lock status. If youpress [SHIFT] and [CAPS], a letter "A" is displayed,indicating all input will be in upper-case. Similarly, an"a" indicates lower case, while a heart character [ ] isshown when all key-presses are to be interpreted as [CONTROL]characters. This occurs when you press [CONTROL]-[CAPS].MODE also indicates whether input is in inverse video ornormal mode. ROW, COLUMN shows the current cursor position. Inaddition to the GRAPHICS 0 cursor, the position of theinvisible graphics cursor is displayed as well. Note that inGRAPHICS 7 or 8, garbage will appear here if a number isgreater than 40. FREE provides a hexadecimal display of how many freebytes of memory are available to the BASIC programmer. Freememory is calculated by subtracting the value of MEMTOP (topof memory) from LOMEM (bottom of memory). MEMTOP is a two-byte pointer to the top of BASIC memory.To determine MEMTOP, take the value found in memory location145 ($91) and multiply it by 256. Add this number to thevalue found in location 144 ($90). In other words: MEMTOP=PEEK(145)*256 + PEEK(144) LOMEM may be calculated similarly using memory locations128 and 129 ($80, $81). LOMEM is maintained by BASICand must not be confused with the operating system's MEMLO. Once invoked, The Informer stays at the top of thescreen until the computer is turned off, or the DeferredVertical Blank vector (VVBLKD, locations 548-549($0224-$0225)) is reset. If you switch screen modes, The Informer's status linewill redraw itself at the top of the new display. Evenpressing [RESET] will not disturb The Informer. And since itsits above the screen that Atari uses, The Informer will nothamper program operation. The Informer status line disappears during time-criticalperiods such as disk I/O. It reappears, updated and ready togo, when the critical period is over. This line replaces oneof the BLANK 8 LINES instructions in the ANTIC display list.You can disable The Informer by pressing[OPTION] [SHIFT]-[RESET]. Reinstate it with [SHIFT]-[RESET].This routine will not work with the Atari Editor/Assemblercartridge because the cartridge squelches all deferrredvertical blanks. Download INFORM.ARC. Use the ARC utilities in the8-bit section of SIG*ATARI to extract INFORMER.EXE andINFORMER.M65, the MAC/65 source code. To use The Informer, copy INFORMER.EXE to another disk(make sure the disk has the DOS.SYS file on it!). Next,change the name of INFORMER.EXE to AUTORUN.SYS. Now, re-bootyour Atari with this disk, and The Informer will appear. (bio) Cousins Matt Loveless and Mike Eggers were both in theirmid-teens when Page 6 was originally released on disk bySynapse Software in 1982.
