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The PowerBASIC Wizard's Library =-----------------------------= Version 1.2 PBWIZ Copyright (c) 1991-1992 Thomas G. Hanlin III This is PBWiz, a library of assembly language and BASIC routines for use with PowerBASIC version 2.x. Full source code is available with registration. The PBWiz collection is copyrighted and may be distributed only under the following conditions: 1) All PBWiz files must be distributed together in original, unaltered form. A list of the 16 files included may be found in FILES.LST. 2) No files may be added to the PBWiz collection. This applies specifically to the practice of adding files containing BBS ads to archives. I find this seriously offensive. You use this library at your own risk. It has been tested by me on my own computer, but I will not assume any responsibility for any problems which PBWiz may cause you. If you do encounter a problem, please let me know about it, and I will do my best to verify and repair the error. It is expected that if you find PBWiz useful, you will register your copy. You may not use PBWiz routines in programs intended for sale unless you have registered. Registration entitles you to receive the latest version of PBWiz, complete with full source code in assembly language and BASIC. The assembly code is designed for the MASM 6.0 assembler and may require minor modifications if you wish to use it with OPTASM, TASM, or earlier versions of MASM. Warning: Unregistered use of PBWiz for more than 30 days may encourage the author to sing Gregorian chants under your window. Don't let this happen to you! Table of Contents page 2 Synopsis and Legal Info .................................... 1 Table of Contents .......................................... 2 Overview ................................................... 3 Archives ................................................... 4 Dates and Times ............................................ 6 Equipment Info ............................................. 7 Extended Math ............................................. 11 Graphics .................................................. 14 Keyboard .................................................. 17 Memory (EMS) .............................................. 21 Memory (XMS) .............................................. 24 Mouse Support ............................................. 26 Strings ................................................... 29 Text-mode Video ........................................... 32 Credits ................................................... 36 Overview page 3 Any program that uses any of the PBWiz routines must DECLARE them appropriately. To make this easy, I've created a single file which contains all of the necessary declarations. Put the following line at the top of your program to use it: $INCLUDE "PBWIZ.INC" The DECLARE statements contained in this file tell PowerBASIC how to behave when it runs into any PBWiz routines. They don't actually load the routines. To do that, you must $LINK the appropriate units. The names of the units to $LINK are specified in each chapter of this manual. Each chapter covers a specific unit or pair of units. If the code is written in assembly language, the unit name ends in A. If the code is written in PowerBASIC, the unit name ends in B. So, for instance, the VIDEO units are called VIDEOA.OBJ and VIDEOB.PBU. If the code for a chapter is written entirely in one language, I don't bother with -A or -B suffix. Archives page 4 When I started in the microcomputer industry, there was a small variety of file archivers, all (more or less) compatible. They did not provide compression, which was relegated to another large selection of more-or-less compatible utilities. Then came SEA's ARC. It was very slow, but it did compression as well as archiving, and included CRC checks so you could know whether the files were intact. It swept the BBS scene in short order, becoming the new standard. A few other archivers competed on about a level footing, providing only minor variances on the ARC theme. Then SEA decided to sue one of its more successful competitors, Phil Katz (PKARC). The end result was the ZIP standard... but in the chaos resulting from the breaking of the ARC standard, many other archivers came into being: ARJ, LZH, PAK, ZOO, and so forth. PBWiz helps resolve the confusion by providing a single set of routines which allow you to view the contents of archives in any of the above-mentioned formats: ARC, ARJ, LZH, PAK, ZIP, or ZOO. Only archive directories are provided at this time. Other formats will also be added as they arise. If you have details on the format of an archive that you'd like me to add, please send them my way. I'll do what I can to get it into PBWiz. This unit requires the STRING unit (discussed later) as well. To use it in your program, you need to include both units: $LINK "stringa.obj" $LINK "stringb.pbu" $LINK "archives.pbu" Viewing archive directories is handled in roughly the same fashion as you might view a DOS file directory. This makes it possible to treat an archive and a subdirectory in a similar manner. When you're looking for the first file in an archive, use the FindFirstA function. You must specify the archive name and a file name. The archive name may include a drive and path specification, and does not need to have the archive extension. If you leave off the extension, FindFirstA will use the first archive it comes across that matches the rest of the specification. Note that the archive specification may not contain wildcards. In contrast, the search file name may not contain drive or path specs, but may contain wildcards. CALL FindFirstA (Archive$, Filename$, ErrCode%) Archives page 5 If there are no files to be found, or if the archive specification was bad, an error code will be returned. If there was no error, there may well be more files to be found. You can find each of them with FindNextA: CALL FindNextA (ErrCode%) Of course, just finding a matching file doesn't do you much good unless you can retrieve information about it. You can use any of the following routines to provide information about a matched file: Nam$ = GetNameA$ Dat$ = GetDateA$ Tim$ = GetTimeA$ CRC$ = GetCRCA$ StorageMethod$ = GetStoreA$ CALL GetSizeA (OriginalSize&, CurrentSize&) When you're done viewing an archive, be sure to close it: CALL CloseA Let's try an example. Given that you've already written the $LINK line as specified on the previous page, you could see all of the files in an archive using a program like this: CALL FindFirstA (Archive$, "*.*", ErrCode%) DO UNTIL ErrCode% PRINT GetNameA$ CALL FindNextA (ErrCode%) LOOP CALL FCloseA This program fragment also assumes that you have set Archive$ to the name of an archive. It might be convenient to set it to the command line for testing purposes: Archive$ = UCASE$(LTRIM$(RTRIM$(COMMAND$))) Dates and Times page 6 This unit allows you to validate and compare dates. It also provides the day of the week, given the date. Dates may not be before the year 1900. Date strings may be in the form "01/01/91" or "01-01-1991" (the delimiter is not significant and years may be two or four digits; two-digit years will be assumed to be in the 20th century). To use the routines in this unit, include the following line at the top of your program: $LINK "timedate.pbu" Let's start off with date validation. It's often important to know if a date entered into your program is a valid date. IF GoodDate%(DateSt$) THEN PRINT "The date is valid." It can also be helpful to know on which day of the week a given date falls. Day$ = WeekDay$(DateSt$) There are many useful things you can accomplish by turning a date into a number which represents that date (or vice versa). This allows you to compare two dates, which is important if you want to sort by date; find out what the date will be in a given number of days, or what it was some number of days ago; find the number of days between two dates; display a calendar; and so forth. This is easy to do with PBWiz: DateNr& = Date2Num&(DateSt$) DateSt$ = Num2Date$(DateNr&) The DateNr& represents the number of days since January 1, 1900. This is less than 65,535 for dates that go up to around the year 2070 or so, so you may wish to store the dates in compressed two-byte form if your required range of dates is not that large: CrunchDate% = CVI(LEFT$(MKL$(DateNr&), 2)) This can be reversed simply: DateNr& = CVL(MKI$(CrunchDate%) + STRING$(2, 0)) Note that dates crunched this way are only useful for storage purposes, since the numbers greater than 32,767 are stored as negative numbers due to the signed integer format BASIC uses. You must uncompress them before doing any comparisons or date calculations. Still, for a savings of 50%, it may be worth the hassle to convert back and forth. Equipment Info page 7 The equipment unit gives you information about the computing environment. This includes both installed software and hardware. You can use the equipment information routines by including this line in your program: $LINK "equipmen.obj" The first function allows you to determine if an "enhanced" keyboard (101-key) is installed. It may not be able to figure out what the keyboard is on some older not-quite-clone PCs, in which case it will take the safe way out and report that there is no enhanced keyboard. This function returns -1 if there is an enhanced keyboard present, 0 if not. Enhanced% = KbdType% Want to know the type of processor (CPU) being used? Can do! CPU% = Processor% The results will be reported as a number which can be decoded as follows: 0 NEC V20 1 8088 or 8086 2 80186 3 80286 4 80386 or 80486 If anyone knows how to differentiate between an 80386 and an 80486, please let me know. I've only seen one test which could do it, and it wasn't reliable. Maybe you'd like to check for a CD-ROM drive: Drives% = CDROM% This tells you how many logical drives exist, if there is a CD-ROM available. If not, it will return 0. Note that the CD-ROM installation check conflicts with the GRAPHICS.COM installation check for DOS 4.0, due to some screw-up at IBM or Microsoft. I'm not yet sure whether DOS 5.0 is similarly afflicted. The number of floppy drives installed is retrieved like this: Drives% = Floppies% Equipment Info page 8 There may be up to four floppy drives in a system; however, the AT CMOS data area only directly supports two. This makes it easy to find out what kind of drives the first two are, but not the second two. Oh well, guess we'll have to settle for what we can get, right? CALL FloppyType (Drive1, Drive2) The results from FloppyType are returned as follows: 0 no drive 1 5 1/4" 360K 2 5 1/4" 1.2M 3 3 1/2" 720K 4 3 1/2" 1.44M Result codes of 5-7 are available, but not yet defined. One might guess that the 2.88M drive supported by DOS 5.0 will be drive type 5. Has anybody seen one of those puppies yet? New memory types sure have burgeoned over the years... expanded, extended, and now XMS. There are routines to check all of these: BaseExt& = AllExtMem& ' extended memory installed NowExt& = GetExtM& ' BIOS extended memory available CALL GetEMSm (TotalPages%, FreePages%) ' expanded memory CALL GetXMSm (LargestFree&, TotalFree&) ' XMS memory When you're dealing with extended memory, whether it be BIOS-type or using the XMS standard, the results are returned in kilobytes. Multiply 'em by 1024 to convert to bytes. When you're dealing with expanded memory (EMS), the results are in pages of 16,384 bytes. I might note, by the way, that Microsoft seems to have intentionally crippled the XMS standard. It can only support a maximum of 64 megabytes. This may seem like a lot now, but I can remember when my first PC (a Compaq portable) was the awe of the neighborhood with 384K RAM! A few years down the road, the artificial limitations of XMS are going to be a nuisance. A few more routines to get the versions of the EMS and XMS drivers, if any: CALL GetEMSv (MajorV%, MinorV%) CALL GetXMSv (MajorV%, MinorV%) These return the major and minor version numbers as two separate integers. For example, EMS 4.0 would return major version 4, minor version 0. Equipment Info page 9 It's nice to know a little about the operating environment. With the below routines, you can find out what the DOS version is; what version of 4DOS, if any, is in use; and whether Microsoft Windows is running. CALL GetDOSv (MajorV%, MinorV%) CALL Get4DOSv (MajorV%, MinorV%) CALL WinCheck (MajorV%, MinorV%) These return results as major and minor version numbers, as discussed on the previous page. The Get4DOSv and WinCheck routines return zeroes if 4DOS and Windows, respectively, are not available. There are a couple of curious features of GetDOSv to keep in mind. If the version is 10 or higher, you're running in OS/2 compatibility mode. DOS version 10 is actually OS/2 1.0, version 20 is OS/2 2.0, and so on. Secondly, if you're using DOS 5.0, the version reported may not be 5.0-- DOS 5.0 can be told to reply with a lower version number to allow some older software (which checks for a specific DOS version) to run properly. One final routine that should be of some value is the one that allows you to find out what kind of display is available. It tells you the specific adapter and whether the display is color or monochrome. There is one case in which it can be confused, however-- if the adapter is CGA, the display is assumed to be color, since there is no way for the computer to know any differently. So, although this routine provides a good idea of what is available, it would be a good idea to provide an option to tell the program that a monochrome display is attached. Microsoft normally uses "/B" for this purpose, so that might be a good standard to stick with. CALL GetDisplay (Adapter%, Mono%) IF Mono% THEN PRINT "Monochrome monitor" ELSE PRINT "Color monitor" END IF SELECT CASE Adapter% CASE 1: PRINT "MDA" CASE 2: PRINT "Hercules" CASE 3: PRINT "CGA" CASE 4: PRINT "EGA" CASE 5: PRINT "MCGA" CASE 6: PRINT "VGA" END SELECT Equipment Info page 10 Aside from some of the oldest semi-clones, it's possible to find out what sort of machine you're using by looking at a specific data byte. You can access this as follows: Machine% = PCType% The result will need decoding. Here are some known values: 255 PC or XT 254 XT 253 PCjr 252 PC AT 251 XT 250 PS/2 Model 30 249 PC Convertible 248 PS/2 Model 70 or 80 154 Compaq Portable 45 Compaq Portable Likewise, all but some of the oldest semi-clones maintain a BIOS date value which tells you how old the BIOS ROM is. This can be retrieved with the following routine: BIOSdate$ = PCDate$ If your program is running on one of the rare old machines which don't maintain a valid BIOS date, this routine will return "No Date " instead of an actual date. As far as a program is concerned, DR DOS is essentially the same as MS-DOS. Still, it's always nice to know what sort of operating environment you have. You can find out whether your program is running under DR DOS with the following function: IF DRDOS% THEN PRINT "It's DR DOS" ELSE PRINT "MS-DOS" Extended Math page 11 The extended math unit provides an expression evaluator and extensions to BASIC's math. The math extensions include hyperbolic and inverse trig functions, a few handy constants, conversions, and more. You can use the new math routines by including these lines at the top of your program: $LINK "extmatha.obj" $LINK "extmathb.pbu" The expression evaluator allows you to find the result of an expression contained in a string. Normal algebraic precedence is used, e.g. 4+3*5 evaluates to 19. The usual numeric operators (*, /, +, -, ^) are supported (multiply, divide, add, subtract, and raise to a power). Use of negative numbers is just fine, of course. Parentheses for overriding the default order of operations are also supported. You may use either a double asterisk ("**") or a caret ("^") symbols to indicate exponentiation. To evaluate an expression, you pass it to the evaluator as a string. You will get back either an error code or a single-precision result. Try this example to see how the expression evaluator works: $STACK 4096 $INCLUDE "pbwiz.inc" $LINK "extmath.pbu" DO INPUT "Expression? "; Expr$ IF LEN(Expr$) THEN CALL Evaluate (Expr$, Result!, ErrCode%) IF ErrCode% THEN PRINT "Invalid expression. Error = "; ErrCode% ELSE PRINT "Result: "; Result! END IF END IF LOOP WHILE LEN(Expr$) END An expression evaluator adds convenience to any program that needs to accept numbers. Why make someone reach for a calculator when number crunching is what a computer does best? NOTE: The expression evaluator uses recursion and will require more than the default amount of stack space. That's why the $STACK metacommand is used. Extended Math page 12 The new math functions are pretty much self-explanatory, so I'll just list them here. A few general notes are given on the next page. Result% = GCDI%(Nr1%, Nr2%) ' greatest common denominator Result% = RotateL%(Nr%, Count%) ' rotate left Result% = RotateR%(Nr%, Count%) ' rotate right Result% = ShiftL%(Nr%, Count%) ' shift left Result% = ShiftR%(Nr%, Count%) ' shift right Result& = GCDL&(Nr1&, Nr2&) ' greatest common denominator Result& = RotateLL&(Nr&, Count%) ' rotate left Result& = RotateRL&(Nr&, Count%) ' rotate right Result& = ShiftLL&(Nr&, Count%) ' shift left Result& = ShiftRL&(Nr&, Count%) ' shift right Result! = ArcCosHS!(Nr!) ' inverse hyperbolic cosine Result! = ArcSinHS!(Nr!) ' inverse hyperbolic sine Result! = ArcTanHS!(Nr!) ' inverse hyperbolic tangent Result! = ArcCosS!(Nr!) ' arc cosine (1 >= Nr >= -1) Result! = ArcSinS!(Nr!) ' arc sine (1 >= Nr >= -1) Result! = ErfS!(Nr!) ' error function Result! = FactS!(Nr%) ' factorial Result! = CotS!(Nr!) ' cotangent Result! = CscS!(Nr!) ' cosecant Result! = SecS!(Nr!) ' secant Result! = CosHS!(Nr!) ' hyperbolic cosine Result! = SinHS!(Nr!) ' hyperbolic sine Result! = TanHS!(Nr!) ' hyperbolic tangent Result! = Deg2RadS!(Nr!) ' convert degrees to radians Result! = Rad2DegS!(Nr!) ' convert radians to degrees Result! = Cent2Fahr!(Nr!) ' centigrade to Fahrenheit Result! = Fahr2Cent!(Nr!) ' Fahrenheit to centigrade Result! = Kg2Pound!(Nr!) ' convert kilograms to pounds Result! = Pound2Kg!(Nr!) ' convert pounds to kilograms Pi! = PiS! ' the constant "pi" e! = eS! ' the constant "e" Result# = ArcCosHD#(Nr#) ' inverse hyperbolic cosine Result# = ArcSinHD#(Nr#) ' inverse hyperbolic sine Result# = ArcTanHD#(Nr#) ' inverse hyperbolic tangent Result# = ArcCosD#(Nr#) ' arc cosine (1 >= Nr >= -1) Result# = ArcSinD#(Nr#) ' arc sine (1 >= Nr >= -1) Result# = ErfD#(Nr#) ' error function Result# = FactD#(Nr%) ' factorial Result# = CotD#(Nr#) ' cotangent Result# = CscD#(Nr#) ' cosecant Result# = SecD#(Nr#) ' secant Result# = CosHD#(Nr#) ' hyperbolic cosine Result# = SinHD#(Nr#) ' hyperbolic sine Result# = TanHD#(Nr#) ' hyperbolic tangent Result# = Deg2RadD#(Nr#) ' convert degrees to radians Result# = Rad2DegD#(Nr#) ' convert radians to degrees Pi# = PiD# ' the constant "pi" e# = eD# ' the constant "e" Extended Math page 13 Like BASIC's trig functions, these trig functions expect the angle to be in radians. Conversion functions are provided in case you prefer degrees. Note that there is no ArcTanS! or ArcTanD# function for the simple reason that BASIC supplies an ATN function. Constants are expressed to the maximum precision available. If you are not familiar with variable postfix symbols, here's a brief summary: Symbol Meaning Range (approximate) ------ -------- ------------------------------- % integer +- 32767 & long integer +- 2 * 10^9 ! single precision +- 1 * 10^38 # double precision +- 1 * 10^308 See PowerBASIC's online help for further details. Graphics Support page 14 I was rather surprised to find that PowerBASIC lacks support for one of the standard VGA modes-- SCREEN 13, the 320x200 256-color mode. I immediately decided to add support for that mode: dots, lines, boxes, polygons, and (of course) text. While I was at it, I thought I'd add support for a nonstandard VGA mode: 360x480 in 256 colors. This mode will work on almost any plain VGA system, although it might not work on some older not-quite-compatible setups. I'll be adding other modes as I go along, including SuperVGA modes. For now, there are only two modes: 13 320x200, 256 colors, 40x25 text, any VGA N0 360x480, 256 colors, 45x60 text, almost any VGA The graphics routines all use the same nomenclature: a G, followed by a mode number, followed by the specific name. This generic naming convention is used so that this chapter can refer to all available modes. For example, if I say "G#Color" and you're using mode 13, you'd actually use "G13Color" in your program. Ok? There are two sets of routines for each mode-- the ones written in ASM and the ones written in BASIC. The file names for these will be suffixed with "A" for ASM and "B" for BASIC. For instance, to use the SCREEN 13 routines, you would add the following at the top of your program: $LINK "g13a.obj" $LINK "g13b.pbu" The first thing you will always have to do is to put the screen into the proper mode. This is done with the G#Mode routine: CALL G#Mode (Graphics%) Use 0 to switch to text mode or any other value to switch to graphics mode. One difference between BASIC and BasWiz is that, instead of each "draw" command requiring a color parameter as in BASIC, the PBWiz library provides a separate color command: CALL G#Color (Foreground%, Background%) The "foreground" color is used by all graphics routines. The background color is used by the G#Cls routine. Both foreground and background colors are used in the G#Write and G#WriteLn routines. Graphics Support page 15 Here is a list of the corresponding routines, first BASIC, then PBWiz (replace the "#" with the appropriate mode number): ' get the color of a specified point colour% = POINT(x%, y%) colour% = G#GetPel%(x%, y%) ' set the color of a specified point PSET (x%, y%), colour% CALL G#Color (colour%, backgnd%): CALL G#Plot (x%, y%) ' draw a line of a specified color LINE (x1%, y1%) - (x2%, y2%), colour% CALL G#Color (colour%, backgnd%) CALL G#Line (x1%, y1%, x2%, y2%) ' draw a box frame of a specified color LINE (x1%, y1%) - (x2%, y2%), colour%, B CALL G#Color (colour%, backgnd%) CALL G#Box (x1%, y1%, x2%, y2%, 0) ' draw a box of a specified color and fill it in LINE (x1%, y1%) - (x2%, y2%), colour%, BF CALL G#Color (colour%, backgnd%) CALL G#Box (x1%, y1%, x2%, y2%, 1) ' clear the screen and home the cursor CLS CALL G#Cls ' get the current cursor position Row% = CSRLIN: Column% = POS(0) CALL G#GetLocate (Row%, Column%) ' set the current cursor position LOCATE Row%, Column% CALL G#Locate (Row%, Column%) ' display a string without a carriage return and linefeed PRINT St$; CALL G#Write (St$) ' display a string with a carriage return and linefeed PRINT St$ CALL G#WriteLn (St$) Note that PBWiz, unlike BASIC, allows both foreground and background colors for text in graphics mode. Graphics Support page 16 If you need to print a number rather than a string, just use the BASIC function STR$ to convert it. If you don't want a leading space, use this approach: St$ = LTRIM$(STR$(Number)) The PBWiz library has other routines which have no BASIC equivalent. One allows you to get the current colors: CALL G#GetColor (Foreground%, Background%) Circles and ellipses can be drawn with the Ellipse routine. This is similar to the BASIC CIRCLE statement. You specify the center of the ellipse (X,Y), plus the X and Y radius values: CALL G#Ellipse (CenterX%, CenterY%, XRadius%, YRadius%) A circle is an ellipse with a constant radius. So, to draw a circle, just set both radius values to the same value. As well as the usual points, lines, and ellipses, PBWiz also allows you to draw regular polygons: triangles, squares, pentagons, hexagons, and so on. CALL G#Polygon (X%, Y%, Radius%, Vertices%, Angle!) The X% and Y% values represent the coordinates of the center of the polygon. The Radius% is the radius of the polygon (as if you were fitting it into a circle). Vertices% is the number of angles (also the number of sides) for the polygon to have. Angle! specifies the rotation of the polygon, and is specified in radians. Keyboard Control page 17 The keyboard is not a particularly exciting or glamorous device. In fact, we tend to forget about it except when it gets in the way. Sometimes it's a hardware problem-- squishy or clacking keys, or perhaps a commonly-used key placed in an out-of-the-way location. Then again, sometimes it's the software that's the problem. There are many aspects of keyboard control, not all of which are necessarily related to input. This unit will let you handle the keyboard in ways you may not have realized were possible. Better yet, it can help make keyboard control easier than the users of your programs dreamed possible. It all starts with the one little line: $LINK "keyboard.obj" Let's start out with keyboard output. Yep, not input-- output. We can stuff up to 15 keys into the keyboard buffer. Why would we ever want to do this? Perhaps to allow your program to pop-up a TSR automatically, to start another program after your program ends, or for creating key macros. You can enter extended key codes (such as function keys) by using CHR$(0) before the scan code. CALL TypeIn (St$) The usual keyboard action is somewhat sluggish. We can make it a lot crisper by changing the key repeat rate and the delay before repeating begins. This will work on ATs, but not PC/XT systems. CALL SpeedKey (RepDelay%, RepRate%) The delay may be 0-3 (1 by default): 0 250 milliseconds 1 500 milliseconds 2 750 milliseconds 3 1 second The repeat rate may be 0-31 (11 by default). The larger the number, the slower the speed-- 0 is around 30 cps, and 31 is around 2 cps. I generally prefer to have the keyboard cranked up to full speed, using RepDelay% and RepRate% both set to zero. This may be a bit too zippy for some people. Experiment with it to see what you like best. Of course, there may be reasons to make keyboard repeat less sensitive instead! That might be a good idea in programs written for small children, for example. You can adjust the keyboard equally well in either direction. Keyboard Control page 18 PowerBASIC allows you to control one of the keys which can interrupt your program, namely the Break key. There's another dangerous key which PBWiz allows you to control-- the PrtSc (PrintScreen) key. PrtSc may not seem like a hazard at first glance, but if it's pressed by accident with no printer ready, or in a graphics mode which PrtSc doesn't understand how to print, the results can be pretty messy. So, we let you turn it off or back on: CALL SetPrtSc (PrtScON%) Use 0 to turn it off or anything else to turn it back on. If you turn off PrtSc, you MUST remember to turn it back on again before your program ends! Otherwise, an interrupt vector will point into nowhere, causing probable chaos the next time PrtSc is pressed. Regardless of whether you've turned the PrtSc key off, you can print the screen yourself just as if PrtSc had been pressed: CALL PrintScreen Now here's a strange one for you. When IBM brought out the 101-key keyboard, called the "enhanced" keyboard, they did something bizarre to the BIOS. They still allowed old keyboard calls to work, but they filtered out the new key codes so no one would see them. This made sure that no one would be able to use the capabilities of the "enhanced" keyboard without rewriting their programs. So, the keyboard has been around for years, and there are still few programs that even notice when you press F11. PowerBASIC v2.1 does not support the enhanced keyboard at all. Fortunately, PBWiz -does-. You can find out if an enhanced keyboard is installed with the KbdType% function, which is in the Equipment unit. If there is an enhanced keyboard installed, you can activate it like so: CALL SetEnhKbd (Enhanced%) With enhanced keyboard support activated, all key requests that used the old services are translated to the new services. So, SetEnhKbd affects INKEY$ and other BASIC functions as well as other PBWiz keyboard routines. Note that you MUST deactivate enhanced keyboard support before ending your program. Otherwise, an interrupt vector will point into nowhere, probably causing a crash on the next keypress! Keyboard Control page 19 Speaking of INKEY$, I have a neat little function for you. It works like INKEY$, but it doesn't remove the key from the keyboard buffer: ky$ = ScanKey$ How is this handy? Well, let's suppose you're writing something that will work like the DIR or TYPE commands in DOS. It will display what may be a long listing, which you'd like to be able to pause with Ctrl-S or cancel with Ctrl-C. Trouble is, if you use INKEY$ and the user was using "type ahead" to store another command, you've just wiped out his command while looking for those control codes. With ScanKey$, you can check the key nondestructively. On the other hand, if you're about to request important input, you may not want to chance having it answered from results of the keyboard buffer-- could be that the user meant those keys for another purpose. In that case, it's a good approach to clear out the keyboard buffer just before the input: CALL ClearKbd No keyboard unit would be complete without a selection of routines to check the shift states and get or set the keyboard toggles. Let's start with the toggles, which are so called because they get toggled from one state to another: PRINT "Caps Lock : "; IF CapsOn% THEN PRINT "ON" ELSE PRINT "OFF" PRINT "Insert : "; IF InsertOn% THEN PRINT "ON" ELSE PRINT "OFF" PRINT "Num Lock : "; IF NumOn% THEN PRINT "ON" ELSE PRINT "OFF" PRINT "Scroll Lock: "; IF ScrollOn% THEN PRINT "ON" ELSE PRINT "OFF" You can also turn the toggles off or on. It's courteous to restore the original toggle states once you end your program, so you might want to save the original values for that purpose. Then again, I guess that doesn't apply if your program is designed for the specific purpose of setting the toggles! CALL SetCaps (CapsLock%) CALL SetInsert (InsertKey%) CALL SetNum (NumLock%) CALL SetScroll (ScrollLock%) Does anyone actually use ScrollLock for anything? Just wondering... Keyboard Control page 20 The shift keys are unique in many respects. They don't return codes that can be detected with INKEY$ or stuffed into the keyboard buffer; several can be pressed at the same time; and they don't repeat. You can detect 'em with PBWiz, at any rate: IF AltPress% THEN PRINT "An ALT key is pressed." IF CtrlPress% THEN PRINT "A CTRL key is pressed." IF ShiftPress% THEN PRINT "A SHIFT key is pressed." IF LAltPress% THEN PRINT "The LEFT ALT key is pressed." IF LCtrlPress% THEN PRINT "The LEFT CTRL key is pressed." IF LShiftPress% THEN PRINT "The LEFT SHIFT key is pressed." IF RAltPress% THEN PRINT "The RIGHT ALT key is pressed." IF RCtrlPress% THEN PRINT "The RIGHT CTRL key is pressed." IF RShiftPress% THEN PRINT "The RIGHT SHIFT key is pressed." NOTE that LAltPress%, LCtrlPress%, RAltPress%, and RCtrlPress% are ONLY available for enhanced keyboards. They will not return useful results on older keyboards. Memory (EMS) page 21 This unit provides support for expanded memory. It will work with older EMS and EEMS drivers as well as the current EMS 4.0 standard, with the exception of one or two routines (as noted) which take advantage of new capabilities. Expanded memory may be present on any type of computer, from 8088 PCs to 80486 ATs. It usually comes as a hardware board with a software driver for older machines; on ATs, it may be implemented using only a software driver which converts it from extended memory. Drivers have also been written which make a hard disk function as EMS memory. This broad range of use makes EMS support invaluable to programs which need extra memory. EMS can theoretically support up to 1 gigabyte of RAM, although the documented limit as of v4.0 was only 32 megabytes. This unit is called EMS. You can access it by including this line at the top of your program: $LINK "ems.obj" Of course, the first thing you need to know is whether any EMS memory actually exists: IF EMSexists% THEN PRINT "EMS exists" The EMS version may also be retrieved: CALL EMSver (MajorV%, MinorV%) It would be a good idea to check the EMS version if you plan to use any features which are only available as of EMS 4.0, such as reallocation. Besides a mere existence and version checks, you will want to know how much EMS is available: PRINT "Total EMS installed: "; EMStotal% PRINT "Free EMS memory : "; EMSfree% If you actually tried the above two lines, you would get a pair of values which don't seem to mean much. The trick is to multiply them by 16,384 to convert them to bytes. This is because EMS memory is always accessed in pages of 16k bytes each. Any time you are dealing with a quantity of EMS memory, the quantity will be specified as a number of pages. Memory (EMS) page 22 Before we get into the mechanics of accessing EMS memory, I'd like to bring up an optional routine which can improve access speed. It should not be used if your program accesses EMS using routines other than the ones included here in PBWiz. If you only use these EMS routines, though, you will find that it makes some kinds of memory accesses faster. Use 0 for normal (slow) mode. Do not use optimization if you are using more than one EMS handle! CALL EMSopt (Fast%) Ok, let's get down to the nitty gritty. (Where did that expression come from, anyway?!) When you allocate EMS memory, you specify the number of pages you want, which must be at least 1. If the allocation is successful, you are returned a "handle" which you can use to access the allocated memory. Otherwise, you get back an error code. CALL EMSopen (Pages%, Handle%, ErrCode%) There are a limited number of handles available under some EMS drivers. The EMS spec, as of v4.0, allowed for a maximum of 255 handles, and it's not unusual for a driver to support only 20 or so. Bearing in mind that some of these handles may be used up by other applications, such as RAMdisks and caches, this really doesn't allow much leeway. Try to use as few handles as possible! You may well need to store multiple values in different areas of the memory allocated for a single handle, rather than allocating a new area of memory for each value. Suppose you find you need more memory than you first allocated? Or maybe less memory? Well, provided EMS 4.0 or later is in use, you can reallocate the block: CALL EMSresize (Handle%, Pages%, ErrCode%) There is no way to reallocate memory under older versions of EMS. About the best you could do in that case would be to allocate a new area of the desired size, copy over the relevant data from the old area, and then deallocate the original area. Of course, this assumes that there is enough memory available to hold both areas, at least temporarily. When you are finished using EMS, you must be sure to return the memory you allocated to the system. It is IMPORTANT to do this before ending your program. Otherwise, the memory you allocated will be "lost" until the next time you boot the computer. Return the memory for each handle as follows: CALL EMSclose (Handle%) Memory (EMS) page 23 Hmmmm... we've covered EMS detection, status info, allocating memory, freeing memory, resizing memory... what's missing here? Ah! We haven't discussed how to actually access the memory! Accessing EMS memory is quite simple, but it involves a couple of steps. EMS is mapped into a 64k block in the low area of memory (the area under 1M, which can be directly accessed). Since a page is 16k, the EMS block can hold up to four pages at a time. To transfer data between normal memory and EMS memory, you must map the appropriate page(s) of EMS into the EMS block. This is done like so: CALL EMSmap (Handle%, PPage%, VPage%) The PPage% is the physical page, that is, the page number within the EMS block (0-3). The VPage% is the virtual page, which is the number of a page within the EMS memory associated with Handle%. Once you've mapped the desired virtual page into a physical page, it can be accessed using standard PowerBASIC memory commands, such PEEK$ and POKE$. First, set the segment: DEF SEG=EMSseg& The offset within a page may be 0-16,383. To get the appropriate offset within the EMS block, you must add the offset of the page itself. This may be calculated as follows: DataOffset& = OffsetWithinPage% + PageNumber% * 16384& One final note: for best compatibility, it would be good to avoid using physical page 3 (the last 16k of the EMS block). Some EMS drivers don't handle this page with complete accuracy, for technical reasons I'm not going to get into right now. Memory (XMS) page 24 This unit provides support for XMS extended memory. It won't work with extended memory unless an XMS driver is present. Extended memory is only present in AT-class computers. It is not available on older PCs. An XMS driver must also be used. XMS drivers are included with MS-DOS 5.0 and Windows 3.0, among other things, so this is not a major limitation. XMS can address a maximum of 64 megabytes. This unit is called XMS. You access it by including this line at the top of your program: $LINK "xms.obj" The first thing to check is whether any XMS memory exists: IF XMSexists% THEN PRINT "XMS exists" The XMS version may also be retrieved: CALL XMSver (MajorV%, MinorV%) The amount of XMS memory available may be reported in either of two different ways: total amount and largest available block. PRINT "Total XMS free : "; XMStfree& PRINT "Largest free block: "; XMSlfree& XMS memory is manipulated in terms of 1,024 byte blocks, so the amount of free memory is reported in kilobytes. Any time you are dealing with a quantity of EMS memory, the quantity will be specified as a number of 1K blocks, except as otherwise noted. Memory (XMS) page 25 When you allocate XMS memory, you specify the number of kilobytes that you want. This may be 0-65535, in theory. Dunno, I don't have 64M RAM <grin>. If the allocation is successful, you are returned a "handle" which you can use to access the allocated memory. Otherwise, you get back an error code. CALL XMSopen (KBytes&, Handle%, ErrCode%) There are a limited number of handles available, although the number can be controlled somewhat by a driver parameter. It's probably best to use as few handles as possible, to avoid running out. You may well want to store multiple values in different areas of the memory allocated for a single handle, rather than allocating a new area of memory for each value. Suppose you find you need more memory than you first allocated? Or maybe less memory? Just reallocate the block: CALL XMSresize (Handle%, KBytes&, ErrCode%) When you are finished using XMS, you must be sure to return the memory you allocated to the system. It is IMPORTANT to do this before ending your program. Otherwise, the memory you allocated will be "lost" until the next time you boot the computer. Return the memory for each handle as follows: CALL XMSclose (Handle%) To transfer data between normal memory and XMS memory, you must provide the segment and offset of the normal memory area (use the PowerBASIC functions VARSEG and VARPTR to find the address of a variable). The position within XMS memory is specified as a long-integer offset starting at zero. CALL XMSread (Handle%, Posn&, Bytes&, DSeg%, DOfs%) CALL XMSwrite (Handle%, Posn&, Bytes&, DSeg%, DOfs%) Note that the Bytes& to transfer must be an EVEN NUMBER. It is not restricted to 64k, however, so you can transfer a great deal of data with these routines. The XMS spec guarantees a "reasonable" number of interrupt windows during a transfer; however, it is possible that you might experience some communications dropouts if you do large transfers during high-speed telecommunications. If this is expected to happen, test it carefully. Mouse Support page 26 The mouse unit provides full-featured mouse support. You can see if a mouse is available and how many buttons it has, get the cursor position (either the current position or the position at the last press or release of a specified button), set the cursor position, change the cursor, set the mouse range, get hardware information about the mouse, and so on. This unit is called MOUSE, so you access it by including the following line at the top of your program: $LINK "mouse.obj" There are two unusual mouse modes to be aware of. One is text mode, which is mapped to a 640x200 virtual display. So, to convert the results to text format, you need to divide the cursor position by eight and add one. To convert from text format, subtract one and multiply by eight. The second unusual mode is 320x200 CGA mode, which is also mapped to 640x200. To convert the coordinates to this mode, divide X by two. To convert from this mode, multiply the X coordinate by two. All other modes use the actual display coordinates instead of a bizarro virtual screen. Why the peculiar CGA and text modes? Well, evidently Microsoft never thought there'd be any video adapters besides MDA and CGA, and decided to create a single virtual screen size that worked for all modes. Not a bad idea, I guess, but rather shortsighted. Oh well. One other nuisance that you may run into is that the mouse cursor can't be directly turned on or off. A "cursor visibility" count is maintained-- if the mouse cursor was turned on twice, you'll need to turn it off twice before it will actually disappear. Before using the mouse, you must initialize it. The initialization routine also checks to make sure that a mouse is installed and tells you how many buttons it has. It's best to initialize the mouse after setting the screen mode, so the mouse driver understands what mode you're using. Not all mouse drivers support all screen modes, but you can reasonably expect any current mouse driver to support MDA, CGA, EGA, and VGA. Hercules graphics mode is rarely supported, as it must be set through direct hardware access rather than the standard techniques, so the mouse driver has little way of knowing that you've changed the mode. The mouse routines will work equally well with two-button or three-button rodents. The middle button functions will return 0 with two-button mice. Mouse Support page 27 I won't go into great detail on these routines, because they're pretty much self-explanatory. The mouse is a fairly easy device to deal with. You can initialize the mouse driver like so: Buttons% = MouseInit% This returns the number of mouse buttons available. If there is no mouse, zero will be returned. Initialize the mouse after setting the screen mode. You can make the mouse cursor visible or invisible. It will function just as well in either state. See the previous page for some quirks. CALL MouseShow ' show the cursor CALL MouseHide ' hide the cursor There are many ways to get the mouse cursor position. You can get the current position, the position at which the mouse was located when a particular button was pressed, or the position when a button was released. If you choose a past position, you can also find out how many presses or releases of the button have taken place since you last checked. X% = MouseWhereX% ' current X coordinate Y% = MouseWhereY% ' current Y coordinate CALL MouseLClick (Count%, X%, Y%) ' left presses & posn CALL MouseMClick (Count%, X%, Y%) ' middle presses & posn CALL MouseRClick (Count%, X%, Y%) ' right presses & posn CALL MouseLRelease (Count%, X%, Y%) ' left releases & posn CALL MouseMRelease (Count%, X%, Y%) ' middle releases & posn CALL MouseRRelease (Count%, X%, Y%) ' right releases & posn If you'd prefer to find out which buttons are currently pressed, no problem: Pressed% = MouseLButton% ' whether left button is pressed Pressed% = MouseMButton% ' whether middle button is pressed Pressed% = MouseRButton% ' whether right button is pressed Of course, you can also set the cursor location: CALL MouseLocate (X%, Y%) ' set the mouse cursor position The mouse cursor range can be restricted to a given area of the screen. This area is expressed by giving the upper left corner and lower right corner of the rectangular area to which to restrict the cursor. CALL MouseWindow (X1%, Y1%, X2%, Y2%) Mouse Support page 28 There are a variety of cursor shapes available for graphics mode: 0 hourglass ("please wait, program is working" symbol) 1 pointing arrow (default) 2 pointing hand 3 crosshair 4 target (box in a box) 5 grabbing hand If you have ideas for more, let me know and I'll see what I can do. Cursor shapes are not unduly difficult to define. The cursor image is set like so: CALL MouseCursorG (CursorNr%) Strings page 29 One of the true strengths of BASIC lies in its powerful string handling capability. I'd be remiss if I didn't provide extensions which improve it even further. This unit can be accessed by including this line at the top of your program: $LINK "stringa.obj" $LINK "stringb.pbu" The simplest of the PBWiz string routines may seem somewhat whimsical, but it has proven useful to me on several occasions in the past. It reverses the order of characters in a string. CALL Reverse (St$) One of the places this has come in useful is in searching a string from the end-- a reverse INSTR routine: CALL RInstr (MainSt$, SubSt$, Posn%) Rather than returning the first occurrence of a substring within a main string, it returns the last occurrence. Another handy string search allows you to search for various types of characters, rather than a specific substring: CALL TInstr (MainSt$, Types%, Posn%) The type(s) may be specified using any combination of the following. Just add them together. 1 alphabetic 2 numeric 4 symbolic 8 control 16 graphics 32 space Since you can search for any specific types, you can also readily invert the search to look for any characters that are NOT of a given type or types: Types% = NOT Types% This gives you complete control. A typical use for TInstr might be to clean up user input and make sure that it's valid. It's also good for parsing. Strings page 30 Another routine that is useful for cleaning up and parsing user input is called Crunch. It allows you to eliminate adjacent duplicates of a character or list of characters. One use for this, for instance, would be to eliminate repeated spaces, converting an input string from "*.* *.BAK /B" to a more manageable "*.* *.BAK /B". Result$ = Crunch$(St$, CharList$) There are a pair of routines that you'll find valuable if you need to check the validity of a string. These are designed to be compatible with the Xmodem and Ymodem file transfer protocols, so you can use them for error checking in telecommunications as well. Chk% = CheckSum% (St$) CALL CRC16 (St$, HiCRC%, LoCRC%) Another pair of string routines provide a simple encryption and decryption system for text. The method used is not particularly secure but are very fast and will be adequate for many purposes. As always, it helps to use a long and/or complex password. CALL Cipher (St$, Password$) CALL CipherP (St$, Password$) Both of these routines will encipher text on the first run-through and decipher on the second, so you can use the same routine either to encrypt or decrypt a message. They are different in one respect: the encrypted result of Cipher may contain control characters, so it can't be used in a plain sequential-access file. The CipherP routine does not allow use of extended ASCII characters (CHR$(128) - CHR$(255)), as it sets the high bit on each character after encrypting it. This causes the results of CipherP to be printable (and useful in sequential-access files), although they will look very strange. The strings are encrypted (or decrypted) in place. This provides a certain extra measure of security for encryption-- the original plaintext strings are not left floating around in memory where someone might see them. One function is as much a file manipulation routine as it is a string function. It allows you to compare a file name to a file pattern (which may contain wildcards) to see if they match. Only bare filespecs are supported-- you may not use drive or path specifications in the names. IF MatchFile% (Pattern$, Filename$) THEN PRINT Filename$ Strings page 31 The MatchFile function can be used in creating your own DOS-style utilities: DIR, COPY, and so forth. Besides the usual "accept file if it matches" approach, it can also be used to implement the opposite: "exclude file if it matches." This gives you more flexibility than DOS itself supplies. The PowerBASIC compiler provides a very nice function called Extract$. This allows you to retrieve a substring running from the left side of a main string to a specified character delimiter. Not bad, but it might be handy to be able to grab a numbered substring from any part of a main string, and to be able to use a substring delimiter. For instance, you might load a record from a database which contains an address, where each line is delimited by a carriage return and linefeed. Rather than mucking around with Extract$, which really wasn't designed with that sort of thing in mind, you'd do better to use the PBWiz function called DelimExtract$: SubSt$ = DelimExtract$(St$, Delimiter$, Index%) The index starts at 1 with the first substring. If you choose the index of a substring which doesn't actually exist, a null string will be returned. Text-mode Video page 32 Routines in this unit may be accessed if you include these lines at the top of your program: $LINK "videoa.obj" $LINK "videob.pbu" The graphical interface has become a "sexy" thing to have these days, but there are still many good reasons to work in text mode. It's relatively fast, it works on all monitors, and it's often the most appropriate choice. Graphics is overkill for many applications. Besides, you can't redirect graphics to a file or to the printer. Come to think of it, text displayed by the PRINT statement can't be redirected either. Fortunately, we can fix that. All it takes is sending the output through DOS: CALL DOSPrint (St$) ' print to the current output device A nice thing about DOS output is that ANSI display codes will work if you have an ANSI driver (such as ANSI.SYS) installed. If you're working with existing text, such as captured output from a BBS or from an ANSI art program like TheDraw, you can just use the DOSPrint routine to handle it. If you're looking to do your own ANSI output, though, there's an easier way than looking up the individual codes and sending 'em out one at a time. The following routines send the appropriate ANSI codes to the current DOS output device: CALL DOSCls ' clear the screen CALL DOSColor (Fore%, Back%) ' set the screen colors CALL DOSLocate (Row%, Column%) ' set the cursor position The primary advantage of DOS output is that it can be intercepted. It normally goes to the screen, but you can redirect it to a file, printer, or comm port, among other things. You can also be sure that DOS output will work reasonably in a multitasking environment like DESQview or Windows, instead of messing up the screen. The disadvantage is that DOS output is fairly slow. It's great for command line utilities, but not if you plan to do any fancy screen work. For that, you probably want direct-access techniques. The direct screen access provided by PBWiz is rude, crude... and faster than a greased euphemism. It can't be redirected, doesn't handle control codes, and won't even update the cursor position. In return for this lack of amenities, it gives you two very valuable things: complete control and raw speed. Text-mode Video page 33 The direct-access replacement for PRINT works like so: CALL XQPrint (St$, Row%, Column%, Attr%) Now, you might guess that St$ is the text to print, and Row% and Column% are where to print it. The Attr% may seem a bit more opaque. The Attr% is the color to use-- actually, both the foreground and background colors. These are combined into a single value because that's the way the display controller wants to see it. Remember, the emphasis here is on speed, not necessarily convenience! So how do you calculate an attribute given the foreground and background colors? Attr% = CalcAttr% (Fore%, Back%) An Attr% value is never less than 0 or greater than 255-- it will fit into a single byte. That may be useful to know for storage purposes. In any event, keep the Attr% in mind, because we'll be seeing more of it in the future. By the way, you can unpack an attribute into foreground and background colors too, if need be: CALL UnCalcAttr (Attr%, Fore%, Back%) The direct-access routines allow for one, and only one, option which might slow them down. Way back in the dawn of time, when IBM brought out the CGA, they knew that software was cheap and hardware expensive. Besides, no one would be so rash as to bypass the BIOS and DOS routines provided by IBM, so who would notice? Well... of course, it didn't work out that way. The BIOS and DOS display routines are far too slow and cumbersome for many purposes. However, the damage was done-- the IBM CGA, and many (though not all) CGAs since then, flickers horribly if you access its display memory directly. There is a software fix, but it slows the display down tremendously. Still, if your program is run on such a CGA, you'll want to stop the flickering. This may be done so: CALL AntiSnow (Slow%) ' any nonzero value to stop flicker You should provide a command-line switch or configuration option to force anti-flicker support. Don't do it by default, as the slowdown is very noticeable. The "menu" approach has become the standard way of allowing a user to choose between various program options. There are many ways of designing a menu, but they almost always require a "highlight" to show the current choice. This highlight is generally handled by changing the color of the chosen item: CALL ReColorArea (TopRow%, LftCol%, BotRow%, RtCol%, Attr%) Text-mode Video page 34 Pop-up windows have become ubiquitous. Naturally, PBWiz supports them too: CALL PopWindow (TRow%, LCol%, BRow%, RCol%, Frame%, Attr%, Grow%, Shade%, TFore%, Title$) ' use one line! The first four parameters specify the upper left corner and lower right corner of the window. The window frame, if any, is created just outside these coordinates. If you choose a shadow for a 3D effect, that will extend further outside the window. Keep this in mind if you want to save the part of the screen under the window... but we'll get to that! Let's see what options are available for the frame type: 0 no frame 1 single lines 2 double lines 3 single horizontal, double vertical lines 4 double horizontal, single vertical lines 5 block graphic lines These are the available shadows: -3 transparent shadow on the right -2 transparent shadow on the left -1 solid black shadow on the left 0 no shadow 1+ shadow attribute (use CalcAttr) for a colored shadow Options for growing windows are as follows: -1 grow as fast as possible 0 pop onto the screen 1+ grow with a specified delay in milliseconds (15 works well for me) The TFore% parameter is the foreground color to use for the title (Title$), if any (use "" for no title). It is worth noting that the "milliseconds" value is only rather approximate. The delay is based on the video card, and is fairly similar on any computer system, but there will be a noticeable difference between (say) an XT with a CGA and a 486 with a VGA. Still, it's a useful delay-- if not really precise, it's at least fairly accurate, and it has a fine resolution. You can access this delay yourself: CALL DelayV (MilliSeconds%) Text-mode Video page 35 I mentioned screen saves a bit earlier. With PBWiz, you can save any part of a screen, and restore it later to the same place or an entirely different area. This also offers the possibility of creating a screen image, storing it in a file, and reading it into your program, among other things. It works like this: Scr$ = ScreenSave$ (TopRow%, LftCol%, BotRow%, RtCol%) CALL ScreenRestore (Scr$, TopRow%, LftCol%) It takes about 4K to store a full 80x25 text screen. The exact calculation is Bytes = Rows * Columns * 2 + 2, if you care to figure it out yourself. You can also take advantage of a PBWiz routine to handle it: Bytes% = CalcSize% (TopRow%, LftCol%, BotRow%, RtCol%) + 2 Finally, we are left with a series of routines which let you scroll (or clear) any part of the screen: CALL ScrollDown (TRow%, LCol%, BRow%, RCol%, Times%, Attr%) CALL ScrollLeft (TRow%, LCol%, BRow%, RCol%, Times%, Attr%) CALL ScrollRight (TRow%, LCol%, BRow%, RCol%, Times%, Attr%) CALL ScrollUp (TRow%, LCol%, BRow%, RCol%, Times%, Attr%) If you attempt to scroll zero times, or more times than there are rows (or columns, depending on which way you scroll), the specified area of the screen will be cleared. The Attr% gives the color to use on the cleared area of the screen. Credits page 36 I'd like to thank Dave Navarro for letting me in on the world of PowerBASIC. His assistance has been most valuable to me in many respects. Without him, this library would have taken much longer to get off the ground or would perhaps not even exist. I would also like to thank Spectra, publishers of PowerBASIC, for sending me the evaluation copy of PowerBASIC which led to my decision to write this library.