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Text File | 1987-12-23 | 22KB | 454 lines

New items for this release 12/23/87: Part 1 - TYPE..END TYPE Part 2 - Long Integers Part 3 - Sample program #2 ------------------------------------------------------------------------- This file contains information about bugs, quirks, and general points of interest to programmers working with compiled BASIC. It is divided into three parts: Part 1 - Description of bugs, quirks and errors Part 2 - General points of interest Part 3 - Sample programs If you want to find one of the above quickly, use your text editor to search for the text shown above. i.e., Search for "Part 1 -". This file was compiled by Mark Novisoff of MicroHelp, Inc. Much of the information was contributed by members of MicroHelp's BASIC Users Group. If you have additional information that should be added, please send it to: Mark Novisoff MicroHelp, Inc. 2220 Carlyle Drive Marietta GA 30062 (404) 973-9272 Compuserve ID 73047,3706 in MSSYS (Microsoft Systems Forum) Part 1 - Description of bugs, quirks and errors Command/Error Compilers Description -------------- --------------- -------------------------------------------- CALL (asm) QB 4 Effective with QB 4, assembly language subroutines must preserve the SI and DI registers and make sure the direction flag is cleared before returning to BASIC. CALL INIT QB 2-3 Do not name a precompiled subprogram "INIT". If you do, the compiler will go into never- never land when your user library is loaded. CALL vs GOSUB All If you have many calls to the same asm routine or subprogram, you'll use less memory if you set variables and GOSUB to a routine that performs the CALL instead of having the CALL "in line". CALL is much faster using variables than using "literals". CALLS QB 4 When CALLS (note the "S") is used and you compile with "/D" (debug), the segment of of a string element descriptor does not get passed on the stack. In other words, if you have an assembly language subroutine that uses CALLS, you should not compile with "/d". CHAIN QB 4 Unreliable when using DOS 2.x. CIRCLE QB 4 The start and end angles must be LESS than 2*pi. Previously they could be less than or equal to. CLEAR,,Size QB 3,4 If you receive an out of stack space message. The stack size is not reset between CHAIN'ing but if you CHAIN back to your original program, be sure to skip the CLEAR instruction. COMMON and QB 2-4 All statements that use COMMON or variations COMMON SHARED thereon with CHAIN must use parameter lists that match exactly. Best done with $Include. COMMON with TYPE QB 4 The TYPE statement must appear before the COMMON statement and must appear in all programs that use it. The COMMON statement must contain "AS". See sample program #1 at the end of this file. Compile to EXE QB 4 QB issues an unusual LINK command in the form of: LINK Prog+YourLib.Lib; This causes LINK to bring the entire library into your program! The solution is to exit QB, and run BC and LINK yourself. CONST QB 4 Must be included in all program modules that use the constant. Place in the file at the top, rather than inside SUB's. DATA QB 4 When a DATA statement is encountered inside a SUB...END SUB structure, QB moves it into the "mainline" portion of the code when you are in the environment. DEF FN All Functions are local to the module in which the DEF FN appears. Use QB 4's FUNCTION..END FUNCTION for global functions. DIM QB 4 Static numeric arrays are stored on the "heap" when you are inside the QB 4 environment. BC programs store them in the default DS. DIM (TYPE) QB 4 See sample program #1 for dimensioning arrays of TYPE'd variables. Division All Using integer division "\" when an integer result is desired is much faster than normal division "/". DRAW QB 2-4 Does not respect the boundaries designated by WINDOW. FRE(-1) QB 4 If a Quick Library is loaded, this value may return incorrectly. QB 4 seems to forget that the library is loaded and thinks that the space is available. But, QB 4 won't let you use the space for dynamic arrays. FRE("") QB 4 Using BRUN gives approximately 4K more than BCOM. FUNCTION QB 4 Provides global functions for all modules in a program. All that is needed is a DECLARE statement in any module that needs to use the function. In addition, this type of function can be recursive. See DEF FN. FUNCTION QB 4 Cannot be used in $Include files. IF..THEN..ELSE QB 3 More than two nestings for ELSE on a single line will not compiler properly. HEX$ QB 4 Be careful when using with non-integer values. For example, the output from the two lines shown is "FFFF8002". E&=&H8002 PRINT HEX$(E&) LINK All Use the /EXEPACK switch to condense the file. Can be used on any program except programs that are CHAIN'ed to using all compilers except QB 4. All QB 4 programs can use this switch. Syntax: LINK /EXE Progname (etc.) LINK QB 4 When building a Quick Library, be sure to specify BQLB40 in the library field. Example: LINK /QU ObjMods,Lib,,BQLB40; LOAD QB 4 If you receive an "out of memory" error, try breaking your program into logical pieces (using subprograms). Then use COMMON SHARED for all variables that you need in the entire program. The exact same COMMON SHARED declaration must appear in all the modules in the program that need access to the variables. LOAD QB 4 If you download a QB 4 program in "fast load" format, many modem transfer protocols pad the file out using a number of CHR$(0)'s. This will cause QB 4 to crash when you attempt to load the program. Use DEBUG to view the file, then write the program to disk after changing the CX register to shorten the length of the file so that the trailing CHR$(0)'s are not included. The other solution is to download this type of file using an ARC program that restores the original length of the file. ON ERROR QB 2-4 Error handler routines must be located outside SUB...END SUB structures. You can RESUME to a line number/label that is outside SUB...END SUB structures (using /E) or to code inside the sub using plain RESUME or RESUME NEXT (/X). Much better is to $Include subroutines that perform error trapping instead of having them in subprograms. This allows the use of RESUME line number/ label and avoids the /X. OPEN All With Novell NetWare, using OPEN on a file that does not exist does not always create the file. Novell has acknowledged the problem but no solution is available as of 12/19/87. Overflow All BASIC uses integer types for all calculations and processes the right side of the equal sign before the left side. To force BASIC to use a different numeric type, place a type identifier on the right of the equal sign. Example: A=Peek(2)+256!*Peek(3) RESUME All If you always use RESUME <linenumber> or RESUME <label> you can use the "/e" switch instead of "/x". Makes programs smaller! This is not practical for subprograms, so error trapping is better handled in mainline code. See ON ERROR. RESUME QB 4 If you compile to an EXE from inside the environment, a "/X" is generated by QB even though it's not needed. Be sure to recompile with "/E" outside of the environment if your program doesn't need "/X". SADD QB 4 When using SADD-188 for Btrieve, be sure to make this calculation EACH TIME you are going to CALL Btrieve. This is because QB 4 can move the FIELD'ed strings around in memory. SAVE QB 4 If you edit a new program and save it, QB defaults to "fast load" format. The file cannot be handled by a text editor. Fix by using "save as". SELECT CASE QB 4 Doesn't allow periods in variable names that are "plain" variables. If using a TYPE'd record element (which does indeed use periods), QB 4 will accept that with no problem. SIGNAL QB 4 Keyword reserved for future use. SLEEP QB 4 Keyword reserved for future use. SOUND QB 3/87 Generates error 6 in all forms when the emulator is used on non-87 machines. STATIC QB 4 When used with a subprogram, makes the subprogram faster, since local variables are not initialized on each call. String Space QB 4 Drops you out to DOS without saving Corrupt your program. The solution is to save often! STRING$ All A$=String$(5,65) takes less code than A$=String$(5,"A") and both are smaller than A$="AAAAA". SUB...END SUB QB 4 Cannot be used in $Include files. Cannot have the same name as a variable (regardless of the variable type). TYPE..END TYPE QB 4 There has been an unverified problem reported in QB when the record length is an odd number. A "FAR HEAP CORRUPT" error is generated. The problem reportedly occurs when the record length is an odd number of bytes. It does not seem to appear in BC, only QB. If you have an unusual, otherwise unexplained problem, try changing the record length to an even number. TYPE..END TYPE (with COMMON) QB 4 See COMMON (with TYPE) and sample program #1. VAL QB 4 Generates an error (rather than value of 0) when "%" is the first character in the string. WINDOW QB 2-4 Does not affect DRAW statements. ---------------------------------------------------------------------------- Part 2 - General points of interest ---------------------------------------------------------------------------- Long integers with QB 4 When you have a long integer array with two dimensions, BC does not handle the zeroth elements correctly, but QB works with it OK. The fix is not to use the zeroth elements. Secondly, if you dimension the same two-dimensional array using a variable name instead of a numeric constant, BC cannot handle your array at all! The fix is to use only constant numbers in dimensioning the array. Another fix that DOES work with dynamic arrays, is to use the /R switch when compiling. ---------------------------------------------------------------------------- More on long integers If you pass a long integer array to a subprogram, QB will work OK, but BC does not. See Sample Program #2. ---------------------------------------------------------------------------- LIB environment variable If you set the LIB environment variable, you will find that QB, BC, BUILDLIB and LINK will all search the specified path whenever a User Lib, Quick Lib or LINK lib is needed. The syntax is similar to the DOS Path syntax: SET LIB=C:\Libs;C:\DOS;C:\QB ---------------------------------------------------------------------------- Undocumented switches in QuickBASIC 3 QB ProgramName/F compiles the specified program to an EXE file without starting up the QB editor. QB ProgramName/Z tells QB to load and execute ProgramName and exit to DOS when the program ends. ---------------------------------------------------------------------------- Response files BUILDLIB and LINK both accept input from response files. This is exactly the same as redirection of input, but the programs will continue running when the end of the file is reached prematurely. Example: Response file contains: Prog1+Prog2+Prog3+ Prog4+Prog5+Prog6 Rem Don't include ANY additional blank lines Buildlib batch file contains: Buildlib @Response.Fil,MyLib.Exe; Buildlib will take its input from the response file because the "@" sign tells it to! ---------------------------------------------------------------------------- BUILDLIB and "too many segments" error Where "nnnn" is a number from 1 to 1024, use: BUILDLIB /SEG:nnnn That increases (or decreases) the number of allowable segments. Default=255. ---------------------------------------------------------------------------- Patching QB 4 menu and help colors. This color table in this file was uploaded by Dave Engfer to the MicroHelp Basic Users Group BBS. If you don't like the colors that QB 4.0 uses, you can patch it to show the colors you want. In order to effect your patches, do the following: Make a backup copy of QB.EXE. REN QB.EXE QB <Enter> DEBUG QB <Enter> R <Enter> At this point, debug will show you the current register settings and the current instruction. Something like this: -r AX=0000 BX=0003 CX=82A0 etc. DS=xxxx ES=xxxx SS=xxxx etc. xxxx:0100 RD DEC BP The "xxxx" is the current code segment. On my machine, the value is 2A28. The color table that QB uses is located near the end of the QB program, specifically 3 full segments higher than "xxxx". That means you will need to add 3000 hex to the number of the segment shown. In my case, I would patch segment 5A28. Note that adding 3 to the first of the four hex numbers does the trick. Now, with the higher segment address in mind, display the existing color table. Remember, the segment on your machine is most likely different from mine, but the offset "5B6F" should be the same. On my system: d 5A28:5B6F <Enter> gives the following table (on my system, "xxxx" is 5A28): xxxx:5B60 34 xxxx:5B70 30 4F 34 30 38 4F 47 34-38 70 71 74 07 47 0A 30 xxxx:5B80 3F 17 4A 00 07 70 70 0F-7F 70 78 0F 07 7F 70 70 etc. Below you'll find a table of the colors and what Dave thinks they represent. Note that some are marked "unknown". Dave suspects they may be related to rodents. You can change your copy of QB to display the various colors by changing the values in the table. The formula for determining color is the same as in Mach 2: Attribute=Background*16+Foreground. As an example, suppose you want to change the "top line highlight" to red on green (XMAS is only a month away!). The color attribute we want (in HEX for debug) is 2*16+4 or 36 decimal or 24 HEX. So, to patch that color: -e xxxx:5B71 24 <Enter> -w <Enter> -q <Enter> REN QB QB.EXE Now, when you hold the Alt key (without pressing anything else), "File" appears in red on green. Original Color Addr Byte Effect --------------------------------------------------------------------- Red on Cyan 5B6F 34 The outline for the pulldown boxes Black on Cyan 5B70 30 The Color for the top line Bright White on Red 5B71 4F Top line Highlight (e.i. press 'Atl' and the option will highlight) Red on Cyan 5B72 34 Top line first letter highlight Black on Cyan 5B73 30 *Pulldown box text and background - 1 Bright Black on Cyan 5B74 38 *Pulldown box text and background - 2 Bright White on Red 5B75 4F *Pulldown box highlight line - 1 White on Red 5B76 47 *Pulldown box highlight line - 2 Red on Cyan 5B77 34 *Pulldown box first letters - 1 Bright Black on Cyan 5B78 38 *Pulldown box first letters - 2 Black on White 5B79 70 Frame around the Help box- Shft F1 Blue on white 5B7A 71 Help box selection area- Shft F1 Red on White 5B7B 74 Help box first letter highlight- F1 5B7C 07 Unknown 5B7D 47 Unknown 5B7E 0A Unknown Black on Cyan 5B7F 30 Bottom line prompt text Bright White on Cyan 5B80 3F Microsoft Copyright Notice Notes- * - Microsoft uses two different color bytes for the pulldown boxes. 1 - This byte seems to be used for options with a highlight letter. 2 - This byte seens to be used for options without a highlight letter. ---------------------------------------------------------------------------- Part 3 - Sample programs ---------------------------------------------------------------------------- Sample program #1. How to use COMMON with TYPE'd variables. ' Prog1.bas TYPE Namerec LastName AS STRING * 20 FirstName AS STRING *15 END TYPE COMMON Filename() AS Namerec DIM Filename(5) AS Namerec Filename(1).LastName="Novisoff" Filename(1).FirstName="Mark" CHAIN "Prog2" ' Prog2.bas TYPE Namerec LastName AS STRING * 20 FirstName AS STRING * 15 END TYPE COMMON Filename() AS Namerec PRINT Filename(1).LastName, Filename(1).FirstName ---------------------------------------------------------------------------- Sample program #2. Demonstrates problem with long integers in subprograms. DECLARE SUB TestLong (LongArray&()) 'Demonstration to show difference between return values of long int ' 'Returns desired value if compiled in the env but not if compiled by BC ' 'This fault only appears if the code is in a subprogram and compiled with BC REM $Dynamic DIM LongArray&(10) DIM MainArray%(10) CLS LongArray&(1) = 100 MainArray%(1) = 10 FOR x% = 1 TO 2 LongArray&(1) = MainArray%(1) + LongArray&(1) NEXT PRINT "TestLong should = 120" PRINT "Long Array from MAIN = "; LongArray&(1) PRINT : PRINT "Same code in a subprogram" PRINT CALL TestLong(LongArray&()) PRINT "TestLong should return 120" PRINT "Long Array from TestLong sub = "; LongArray&(1) SUB TestLong (LongArray&()) DIM IntArray%(10) LongArray&(1) = 100 IntArray%(1) = 10 FOR x% = 1 TO 2 LongArray&(1) = IntArray%(1) + LongArray&(1) NEXT END SUB