What is retained?

[Opry99er]

What all is retained when you do a "RUN DSK1.xxx" from inside an XB program?

 

From what I can tell through the minor testing I have done is that character patterns are retained, but all numeric variables get set to zero and all string variables get set to null.

 

The XB manual talks about the wiping of variables prior to executing the RUN statement, but doesn't go any further than that in it's explanation. What I'm hoping to find out is whether it wipes anything else, or whether JUST the numeric and string variables are wiped.

 

I'm assuming that all the values that get cleaned out are stored in VDP (but that's just an assumption) and I'm not sure the memory locations that are reserved for XB variables.

 

Would there be a way to have all variables in DATA statements and then "READ" them (within a loop) into specific memory locations that do NOT get affected by the wipe?

 

This is more of a curiosity than anything... I am pretty sure an assembly subprogram can be written and then LINKed and LOADed from the XB program itself, and potentially a looped READ from DATA could be used to stick values and strings into non-wiped memory locations. Then again, maybe not.

 

I have some reasons for asking this, but I'm curious to see what you fellas think before I go into much detail.

 

 

Thanks in advance

 

 

 

 

 

 

 

 

 

 

 

[RobertLM78]

You could save them to disk and then reload them at the beginning of the "RUN DSK1.xxxx" program.

[Opry99er]

Yes, I actually already have the disk read/write routines written.

 

Just exploring other possibilities.

 

BTW, nice avatar, homie.

[RXB]

Well the code in GPL of the XB module are included in RXB and the code mostly unchanged except where RXB makes changes and is marked with * RXB PATCH CODE * to indicate changes.

[0655]               *********************************************************
[0656]               *            START OF BASIC INTERPETER
[0657]               *********************************************************
[0658]               * GROM Address >6372 TOPLEV
[0659] 6372 86,A3,71 TOPLEV CLR  V@LODFLG           Initialize temp area
[0660] 6375 35,00,4D        MOVE 77,V@LODFLG,V@LODFLG+1
       6378 A3,72,A3
       637B 71
[0661] 637C BE,74,05        ST   5,@KEYBD          Select full keyboard
[0662] 637F 03              SCAN
[0663] 6380 8E,74           CZ   @KEYBD
[0664] 6382 43,88           BR   G6388             99/4A Console?
[0665] 6384 BE,A3,BB        ST   >01,V@CONFLG      Select 99/4A console
       6387 01
[0666] 6388 86,74    G6388  CLR  @KEYBD
[0667] 638A BF,A3,8C        DST  NLNADD,V@BUFSRT   Initialize edit-buffer start
       638D 02,E2
[0668] 638F BF,A3,8E        DST  NLNADD,V@BUFEND   Initialize edit-buffer end
       6392 02,E2
[0669] 6394 31,00,02        MOVE 2,G@ATNZZ,@INTRIN Get address of ATNZZ
       6397 38,00,32
[0670] 639A B2,38,1F        AND  >1F,@INTRIN       Throw away the BR opcode
[0671] 639D A3,38,00        DADD >5B,@INTRIN       Address of polynomial constan
       63A0 5B
[0672] 63A1 BE,A3,71        ST   >31,V@LODFLG      indicate try auto-boot
       63A4 31
[0673]               *----------------------------------------------------------
[0674]               * Add the following line for fixing "MEMORY FULL" error
[0675]               * occurring during MERGE execution will leave the file open
[0676]               * to disk DSR bug, 5/19/81
[0677] 63A5 86,A3,9E SZNEW  CLR  V@MRGPAB          Initialize merged temporary
[0678]               *                              for PAB pointer
[0679]               *----------------------------------------------------------
[0680] 63A8 BE,73,88        ST   RSTK,@SUBSTK      Load base of subroutine stack
[0681] 63AB 06,69,17        CALL CHRTA2            Load character table
[0682] 63AE 86,45           CLR  @FLAG             Initialize flag byte
[0683] 63B0 87,46           DCLR @BUFLEV           Initialize crunch buffer leve
[0684] 63B2 06,80,12        CALL CLSALL            Close all open files
[0685] 63B5 86,34           CLR  @DATA             Initialize READ/DATA pointer
[0686] 63B7 BF,6E,09        DST  VRAMVS,@VSPTR     Initialize base of value stac
       63BA 58
[0687] 63BB BD,24,6E        DST  @VSPTR,@STVSPT    Save in permanent base
[0688] 63BE BD,A3,88        DST  @VSPTR,V@SAVEVP
       63C1 6E
[0689] 63C2 06,68,C3        CALL INITPG            Initialize program & s.t.
[0690] 63C5 06,A0,18        CALL INTRND            Initialize random number
[0691] 63C8 8E,A3,71        CZ   V@LODFLG
[0692] 63CB 63,D3           BS   TOPL02            If need auto-boot

99/4 GPL-ASSEMBLER (Pass 3) correct                                   PAGE 0015 
EDIT-359
[0693]              
[0694] 63CD 86,A3,71        CLR  V@LODFLG          Won't ever need to do again
[0695] 63D0 06,64,8E G63D0  CALL AUTOLD            Attempt an auto-boot
[0696]               *     Label TOPL02 is used by auto-boot in detection of err
[0697] 63D3          ERRRDY EQU  $
[0698] 63D3 06,6A,84 TOPL02 CALL G6A84             Say READY
[0699] 63D6 00              BYTE 0               *  returns to TOPL15
[0700] 63D7 06,68,C3 TOPL05 CALL INITPG            Initialize program space
[0701] 63DA 06,68,DC TOPL10 CALL KILSYM            Kill the symbol table
[0702] 63DD B2,45,F7 TOPL15 AND  >F7,@FLAG         If error in UDF execution
[0703] 63E0 BE,74,05 G63E0  ST   5,@KEYBD          Select full keyboard
[0704] 63E3 03              SCAN
[0705] 63E4 86,74           CLR  @KEYBD
[0706] 63E6 BE,73,88 TOPL20 ST   RSTK,@SUBSTK      Initialize subroutine stack
[0707] 63E9 BF,20,02 TOPL25 DST  NLNADD,@VARW      Screen addr = lower left corn
       63EC E2
[0708] 63ED 86,80,89        CLR  @RAMFLG           Clear the RAMFLG
[0709] 63F0 86,44           CLR  @PRGFLG           Make sure not in program mode
[0710]               * Check for auto-num mode
[0711] 63F2 DA,45,01        CLOG >01,@FLAG         If auto-num on
[0712] 63F5 64,1E           BS   TOPL35
[0713] 63F7 A1,14,0E        DADD @CURINC,@CURLIN   Generate new line number
[0714] 63FA D2,14,00        CGE  0,@CURLIN         >32767?
[0715] 63FD 64,05           BS   TOPL30
[0716] 63FF B2,45,FE        AND  >FE,@FLAG         If out of range->exit auto-nu
[0717] 6402 05,64,1E        B    TOPL35            Merge in below
[0718]               * Must be a long branch!!
[0719] 6405 D5,30,32 TOPL30 DCEQ @ENLN,@STLN       Line might exist
[0720] 6408 64,12           BS   G6412
[0721] 640A BD,4A,14        DST  @CURLIN,@FAC      Ready for program search
[0722] 640D 0F,7E           XML  SPEED
[0723] 640F 03              BYTE SEETWO          * Search for existence of line
[0724] 6410 65,1D           BS   EDTZ05            COND set = line found
[0725] 6412 0F,83    G6412  XML  SCROLL            Scroll to the next line
[0726] 6414 BD,5E,14        DST  @CURLIN,@ARG2     New line #
[0727] 6417 06,6A,7C        CALL G6A7C             Display the line number
[0728] 641A 91,20           DINC @VARW             Following by a space
[0729] 641C 44,20           BR   G6420
[0730] 641E 0F,83    TOPL35 XML  SCROLL            Scroll the screen
[0731] 6420 BE,A2,E1 G6420  ST   >9E,V@NLNADD-1    Display the prompt character
       6423 9E
[0732] 6424 06,6A,76        CALL G6A76             Read in a line
[0733] 6427 06,D0,AF        CALL SAVLIN            Save input line for recall
[0734]               *    Crunch the input line
[0735] 642A 86,22           CLR  @ERRCOD           Assume no-error return
[0736] 642C BF,0A,08        DST  CRNBUF,@RAMPTR    Initialize crunch pointer
       642F 20
[0737] 6430 0F,7F           XML  CRUNCH            CRUNCH the input line
[0738] 6432 00              BYTE 0              *  Normal crunch mode
[0739] 6433 8A,23    TOPL42 CASE @ERRCOD+1
[0740] 6435 44,45           BR   TOPL45            No error detected
[0741] 6437 49,7C           BR   ERRSYN            *SYNTAX ERROR
[0742] 6439 49,90           BR   ERRBLN            *BAD LINE NUMBER
[0743] 643B 49,94           BR   ERRLTL            *LINE TOO LONG
[0744] 643D 49,86           BR   ERRNTL            *NAME TOO LONG
[0745] 643F 49,80           BR   ERRNQS            *UNMATCHED QUOTES
[0746] 6441 49,9A           BR   ERRCIP            *COMMAND ILLEGAL IN PROGRAM
[0747] 6443 49,A4           BR   ERRIVN            *UNRECOGNIZED CHARACTER
[0748] 6445 8F,4A    TOPL45 DCZ  @FAC              Line # present
[0749] 6447 64,62           BS   TOPL55
[0750] 6449 DA,45,01        CLOG >01,@FLAG         Not AUTONUM
[0751] 644C 44,5B           BR   G645B
[0752] 644E D6,75,0D        CEQ  >0D,@RKEY         Must be up or down
[0753] 6451 64,5B           BS   G645B

99/4 GPL-ASSEMBLER (Pass 3) correct                                   PAGE 0016 
EDIT-359
[0754] 6453 D6,42,01        CEQ  >01,@CHAT         Start EDIT mode
[0755] 6456 44,5B           BR   G645B
[0756] 6458 05,D0,00        B    EDTZZ0
[0757] 645B 06,66,CF G645B  CALL EDITLN            EDIT the line into the progra
[0758] 645E 63,E9           BS   TOPL25            If didn't change the line
[0759] 6460 43,DA           BR   TOPL10
[0760]               *    Jump always
[0761] 6462 D6,42,01 TOPL55 CEQ  >01,@CHAT         If blank line - ignore
[0762] 6465 63,E9           BS   TOPL25
[0763] 6467 D6,A8,20        CEQ  >EB,V@CRNBUF
       646A EB
[0764] 646B 65,C9           BS   SZSIZE
[0765] 646D C6,A8,20        CH   >08,V@CRNBUF      If imperative
       6470 08
[0766]               * GKXB Branch code for new commands DEL, COPY, and MOVE.
[0767] 6471 77,59           BS   NEWCMD            Go here to test for new
[0768]               *                              keywords
[0769] 6473 BF,2C,08        DST  CRNBUF+1,@PGMPTR  Anticipate usage of PGMCHR
       6476 21
[0770] 6477 0F,79           XML  PGMCHR            Prepare CHAT for OLD and SAVE
[0771] 6479 8A,A8,20        CASE V@CRNBUF          Select the keyword
[0772] 647C 43,A5           BR   SZNEW             NEW                 0
[0773] 647E 45,20           BR   SZCONT            CONTINUE            1
[0774] 6480 45,BE           BR   SZLIST            LIST                2
[0775] 6482 45,BA           BR   SZBYE             BYE                 3
[0776] 6484 45,60           BR   SZNUM             NUMBER              4
[0777] 6486 45,B7           BR   SZOLD             OLD                 5
[0778] 6488 46,25           BR   SZRES             RESEQUENCE          6
[0779] 648A 45,AF           BR   SZSAVE            SAVE                7
[0780] 648C 45,C6           BR   SZMERG            MERGE               8
[0781]               *    AUTO-BOOT - attempt a ---->   RUN "DSK1.LOAD"
[0782] 648E 31,00,0B AUTOLD MOVE 11,G@DSCLOD,V@CRNBUF
       6491 A8,20,63
       6494 51
[0783] 6495 BF,2C,08        DST  CRNBUF,@PGMPTR    DSK1.LOAD is in crunch buffer
       6498 20
[0784]               * RXB PATCH CODE *************
[0785]               *      BR   SZRUNL            Go to the RUN "NAME" CODE
[0786] 6499 5A,38           BR   RXBRUN            RXB MENU here that waits for a keypress for 1.5 seconds. 
[0787]               ********************************* RUN *********************
[0788] 649B D6,42,C7 SZRUN  CEQ  >C7,@CHAT        'RUN "NAME" QUOTED STRING
[0789] 649E 44,BF           BR   G64BF
[0790] 64A0 BD,58,2C SZRUNL DST  @PGMPTR,@FAC14    Save pointer to name
[0791] 64A3 0F,79           XML  PGMCHR            Get the length of the string
[0792] 64A5 BC,57,42        ST   @CHAT,@FAC13      Put it in FAC13
[0793] 64A8 86,56           CLR  @FAC12            Make it a double byte
[0794] 64AA A1,2C,56        DADD @FAC12,@PGMPTR    Skip the string
[0795] 64AD 0F,79           XML  PGMCHR            To see there is line no. ahea
[0796] 64AF 06,80,24        CALL G8024             Only RUN "NAME" ?
[0797] 64B2 49,7C           BR   ERRSYN            No - junk on end so error
[0798] 64B4 BE,42,C7        ST   STRINZ,@CHAT      Prepare for LOAD routine
[0799] 64B7 BD,2C,58        DST  @FAC14,@PGMPTR    Restore the saved PGMPTR
[0800] 64BA 06,80,26        CALL OLD1              Load the program
[0801] 64BD 44,DA           BR   SZRUN0            Go ahead from here
[0802]               *                             No RUN "NAME" : just run the
[0803]               *                             current program in memory
[0804] 64BF D6,42,C9 G64BF  CEQ  >C9,@CHAT         Is there a line # after RUN?
[0805] 64C2 44,D5           BR   G64D5             No just a RUN
[0806] 64C4 0F,79    G64C4  XML  PGMCHR            Get the line number
[0807] 64C6 BC,4A,42        ST   @CHAT,@FAC        Put it in FAC for SEETWO
[0808] 64C9 0F,79           XML  PGMCHR
[0809] 64CB BC,4B,42        ST   @CHAT,@FAC1
[0810] 64CE 0F,79           XML  PGMCHR            Should be EOS now
[0811] 64D0 06,80,24        CALL G8024             Is it?

99/4 GPL-ASSEMBLER (Pass 3) correct                                   PAGE 0017 
EDIT-359
[0812] 64D3 64,EA           BS   SZRUN2            Yes - Go ahead from here
[0813]               *                              Just 'RUN'
[0814] 64D5 06,80,24 G64D5  CALL G8024             Should be EOS now
[0815] 64D8 49,7C           BR   ERRSYN            No-SYNTAX ERROR
[0816] 64DA D5,30,32 SZRUN0 DCEQ @ENLN,@STLN       Refuse without program
[0817] 64DD 64,EF           BS   ILLST
[0818] 64DF BD,A3,72        DST  @ENLN,V@START     Defualt to beginning
       64E2 32
[0819] 64E3 A7,A3,72        DSUB 3,V@START         Offset into the table
       64E6 00,03
[0820] 64E8 45,02           BR   SZRUN1            Merge in below
[0821]               *    Jump always
[0822] 64EA D5,30,32 SZRUN2 DCEQ @ENLN,@STLN       Refuse without program
[0823] 64ED 44,F9           BR   G64F9
[0824] 64EF 0F,83    ILLST  XML  SCROLL            Scroll the screen for message
[0825] 64F1 86,44           CLR  @PRGFLG           Prevent line # printing
[0826] 64F3 06,6A,82 WRNNPP CALL G6A82
[0827] 64F6 1D              BYTE 29                * NO PROGRAM PRESENT
[0828] 64F7 43,DD           BR   TOPL15
[0829]               *    Condition can never be set since line 0 is prohibited
[0830] 64F9 0F,7E    G64F9  XML  SPEED
[0831] 64FB 03              BYTE SEETWO          * Find the line in the program
[0832] 64FC 49,8C           BR   ERRLNF            * LINE NOT FOUND
[0833] 64FE BD,A3,72        DST  @EXTRAM,V@START   Program run starts here
       6501 2E
[0834]               * GKXB RUN code for color change.
[0835] 6502 57,74    SZRUN1 BR   RUNPAT            Change colors.
[0836] 6504 06,80,12 G6504  CALL CLSALL            Close any open files
[0837] 6507 92,44           DEC  @PRGFLG           Put it back in execution
[0838] 6509 BC,80,89        ST   @RAMTOP+1,@RAMFLG Set/reset RAMFLG flag -- when
       650C 80,85
[0839] 650E 87,A3,86        DCLR V@SEXTRM           in program mode & ERAM exist
[0840] 6511 87,A3,8A        DCLR V@ERRLN           Disallow CONTINUE after RUN
[0841] 6514 06,68,DC        CALL KILSYM            Reset ERR handling to defualt
[0842] 6517 BE,73,88        ST   RSTK,@SUBSTK      Set the stack empty
[0843] 651A 05,6A,70        B    G6A70
[0844] 651D 05,D0,0D EDTZ05 B    EDTZ00

[Tursi]

The only thing that is preserved is that character definitions and colors are not reset.

 

I /believe/ assembly language routines are preserved but I have not tested this.

 

For carrying data across, you can try CALL LOADs in unused parts of RAM, it's not wiped. A trick I actually did back in the day without memory expansion was to store data with CALL CHAR and read it back in the second program with CALL CHARPAT.

 

But it's a new "RUN", so don't count on anything in the program's state being preserved.

[+OLD CS1]

My Commodore BBS is written mostly in BASIC with a bunch of ML routines for support and tasking. The Commodore BASIC loader has some peculiar restrictions, including screwing with variables. Aside from several custom string manipulation routines, I do two things to prevent this: first, once I define the base system variables I make changes to BASIC and variable table pointers which prevent them from being wiped out, and secondly for variables which are not by this chicanery I perform a garbage collection then stash the new pointers, load the module, then restore the pointers.

 

Can that be done with XB?

[RXB]

The Lower 8K and UPPER 24K are left untouched except for memory pointers are reset.

So the best place is to use unused space in these to places instead of VDP as VDP can be unpredictable.

[+acadiel]

What all is retained when you do a "RUN DSK1.xxx" from inside an XB program?

 

From what I can tell through the minor testing I have done is that character patterns are retained, but all numeric variables get set to zero and all string variables get set to null.

 

The XB manual talks about the wiping of variables prior to executing the RUN statement, but doesn't go any further than that in it's explanation. What I'm hoping to find out is whether it wipes anything else, or whether JUST the numeric and string variables are wiped.

 

I'm assuming that all the values that get cleaned out are stored in VDP (but that's just an assumption) and I'm not sure the memory locations that are reserved for XB variables.

 

Would there be a way to have all variables in DATA statements and then "READ" them (within a loop) into specific memory locations that do NOT get affected by the wipe?

 

This is more of a curiosity than anything... I am pretty sure an assembly subprogram can be written and then LINKed and LOADed from the XB program itself, and potentially a looped READ from DATA could be used to stick values and strings into non-wiped memory locations. Then again, maybe not.

 

I have some reasons for asking this, but I'm curious to see what you fellas think before I go into much detail.

 

 

Thanks in advance

 

 

 

 

 

 

 

 

 

 

 

 

I know this isn't XB, but it'd be cool if you could sandbox XB a little bit to where you could still have an EXPMEM2 to load crap into (upper 24K).

 

If it were a TI BASIC program, I wonder if you really wanted to preload some stuff if you could open EXPMEM2 (with Mini Memory) and if that would get wiped if you preloaded your data into it, and then tried to access (OPEN) it from inside the program for data access. Been a while since I used EXPMEM2, though.

 

Man, I'm getting rusty. Not messing with stuff for over a year will do that to oneself

[+acadiel]

Another thing I just thought of... if you make one of Ksarul's Supercarts, you could write a loader to load the data 8K at a time into the SuperCart banks (32K max). Then (if possible) compile your XB program to run from the E/A 5 part of the Supercart. (I've never used the compiler, so I don't know its limitations). Just simply prod the user to move the switches on the Supercart to Bank 0, 1, 2, or 3 to get to certain data. You could make the whole thing stand alone almost, with just bootstrapping the program from somewhere (disk drive, CF7, HDX, HxC Floppy, etc.)

[+InsaneMultitasker]

I pass information between XB programs using CALL LOAD and CALL PEEK quite often. If you are using the lower 8K for assembly routines and have no memory to spare, the next best place is the 24K area starting at 0xA000 (-24576). The lowest area of 0xA000-0xFFFF is untouched unless you exhaust the entire 24K during run-time. Extended BASIC does not wipe the contents when running one program from another.

 

CALL LOAD(-24576,A,B,C,D) !save values into memory starting at -24576, from variables A,B,C,D

CALL PEEK(-24576,Q,R,S,T) !read the values from memory into variables Q,R,S,T

 

CALL LOAD and CALL PEEK operate on single byte (8-bit) integer values. You cannot save floating point values however, a value larger than 255 can be stored across multiple 8-bit values with some simple math.

 

You can also save and load strings if you pick them apart byte by byte (hopefully I did not make any mistakes:)

 

10 A$="TEST STRING"
20 b=LEN(A$)
30 CALL LOAD(-24576,B)  !save length of string
40 FOR A=1 to B
50 CALL LOAD(-24576+A,ASC(SEG$(A$,A,1))) !Save each character value
60 NEXT A

1 !READ 
10 CALL PEEK(-24576,A) !grab length
20 FOR B=1 to A   
30 CALL PEEK(-24576+B,C)  !read value of the string
40 A$=A$&CHR$(C)
50 NEXT B
60 PRINT A$

A000 is represented as a negative number in decimal. This means A001 is represented by -24575, A002 by -24574, etc. This is good to keep in mind if you only want a single byte out of multiple bytes you saved/loaded.

 

It is much faster to save/load strings with an assembly language link, especially if you want multiple variables. It really depends on your needs and how much info you are trying to pass. As always, there are many ways to perform a similar operation.

[Opry99er]

Precisely the info I was looking for, THANKS GUYS!!!

[RXB]

RXB has a much more easy way to do this.

10 ! SAVE
20 A$="TEST STRING"
30 CALL LOAD(-24576,LEN(A$)) ! LENGTH BYTE
40 CALL MOVES("$R",LEN(A$),A$,-24577) ! MOVES LENGTH, FROM A$ TO RAM ADDRESS



10 ! READ
20 CALL PEEK(-24576,L) ! GET LENGTH BYTE
30 CALL MOVES("R$",L,-24577,A$) ! MOVES LENGTH, FROM RAM ADDRESS TO A$

Edited April 5, 2015 by RXB

[+InsaneMultitasker]

RXB has a much more easy way to do this.

10 ! SAVE
20 A$="TEST STRING"
30 CALL LOAD(-24576,LEN(A$)) ! LENGTH BYTE
40 CALL MOVES("$R",LEN(A$),A$,-24577) ! MOVES LENGTH, FROM A$ TO RAM ADDRESS

10 ! READ
20 CALL PEEK(-24576,L) ! GET LENGTH BYTE
30 CALL MOVES("R$",L,-24577,A$) ! MOVES LENGTH, FROM RAM ADDRESS TO A$

 

Yep, that's nice and simple for those using RXB. One small change: -24577 should be -24575. We could throw more strings after the first by computing the next memory location which in this case would be: -24576+1+LEN(A$)

[RXB]

Something else RXB can do that would be much tougher than normal XB is this one:

100 ! SAVE
110 A$="TEST STRING"
120 B$="ANOTHER TEST STRING"
130 C$="LAST TEST STRING"
140 L=LEN(A$&B$&C$)
150 CALL LOAD(-24576,L)
160 CALL MOVES("$R",L,A$&B$&C$,-24577)

This would be useful for embedding a Assembly program in strings then into Upper 24K.

Like RXB used this for that game I wrote called IN THE DARK and without using a CALL LINK but instead used CALL EXECUTE(address)

CALL LINK requires you to load excess stuff not needed. So I created EXECUTE to fix that issue.

 

And I see your point about the strings, I was just thinking large sections to be saved larger than a string. (255 Characters)

[+Vorticon]

I pass information between XB programs using CALL LOAD and CALL PEEK quite often. If you are using the lower 8K for assembly routines and have no memory to spare, the next best place is the 24K area starting at 0xA000 (-24576). The lowest area of 0xA000-0xFFFF is untouched unless you exhaust the entire 24K during run-time. Extended BASIC does not wipe the contents when running one program from another.

 

CALL LOAD(-24576,A,B,C,D) !save values into memory starting at -24576, from variables A,B,C,D

CALL PEEK(-24576,Q,R,S,T) !read the values from memory into variables Q,R,S,T

 

CALL LOAD and CALL PEEK operate on single byte (8-bit) integer values. You cannot save floating point values however, a value larger than 255 can be stored across multiple 8-bit values with some simple math.

 

You can also save and load strings if you pick them apart byte by byte (hopefully I did not make any mistakes:)

 

10 A$="TEST STRING"
20 b=LEN(A$)
30 CALL LOAD(-24576,B)  !save length of string
40 FOR A=1 to B
50 CALL LOAD(-24576+A,ASC(SEG$(A$,A,1))) !Save each character value
60 NEXT A

1 !READ 
10 CALL PEEK(-24576,A) !grab length
20 FOR B=1 to A   
30 CALL PEEK(-24576+B,C)  !read value of the string
40 A$=A$&CHR$(C)
50 NEXT B
60 PRINT A$

A000 is represented as a negative number in decimal. This means A001 is represented by -24575, A002 by -24574, etc. This is good to keep in mind if you only want a single byte out of multiple bytes you saved/loaded.

 

It is much faster to save/load strings with an assembly language link, especially if you want multiple variables. It really depends on your needs and how much info you are trying to pass. As always, there are many ways to perform a similar operation.

 

 

Well nuts... I wish I knew about this before... When I coded Close Action which has 4 chained programs, I saved the entire state of each program to disk before loading the next and then loaded them back in, which probably slowed down the process... This is really nifty!

[Opry99er]

^^My predicament.

[JamesD]

FWIW, the TRS-80 version of Temple of Apshai was written in BASIC and reserved an area of memory for variables and then appeared to PEEK and POKE to access them with it's different modules.
I think games like Silvern Castle on the Apple have the same issue.
Why more BASICs didn't support the CHAIN command I'll never know.

I think one approach on other BASICs (Microsoft derived at least) was to mess with BASIC's memory pointers.
They tell where variable areas start and where the top of memory is.
By lowering the top of RAM pointer and pointer to variables a program can hide the memory used for variables so it isn't cleared before loading the next BASIC module.
Then the first line of the next module restores the proper addresses and BASIC suddenly sees it all again.
That's a bit of a simplification of what goes on but you get the idea.
I don't know that TI BASIC has equivalents of those pointers though.

[RXB]

FWIW, the TRS-80 version of Temple of Apshai was written in BASIC and reserved an area of memory for variables and then appeared to PEEK and POKE to access them with it's different modules.

I think games like Silvern Castle on the Apple have the same issue.

Why more BASICs didn't support the CHAIN command I'll never know.

 

I think one approach on other BASICs (Microsoft derived at least) was to mess with BASIC's memory pointers.

They tell where variable areas start and where the top of memory is.

By lowering the top of RAM pointer and pointer to variables a program can hide the memory used for variables so it isn't cleared before loading the next BASIC module.

Then the first line of the next module restores the proper addresses and BASIC suddenly sees it all again.

That's a bit of a simplification of what goes on but you get the idea.

I don't know that TI BASIC has equivalents of those pointers though.

TI BASIC ONLY uses VDP memory so all the pointers are in VDP ONLY.

There is not a single RAM pointer in TI BASIC.

(Unless EA module is used but that is for loading and saving RAM and there are no pointers really.)

 

On the other hand XB uses VDP and RAM and has pointers for both to modify and use.

Edited April 6, 2015 by RXB

[JamesD]

TI BASIC ONLY uses VDP memory so all the pointers are in VDP ONLY.

There is not a single RAM pointer in TI BASIC.

(Unless EA module is used but that is for loading and saving RAM and there are no pointers really.)

 

On the other hand XB uses VDP and RAM and has pointers for both to modify and use.

Even VDP RAM would need some sort of allocation scheme. You probably have no mechanism to reserve memory at the top of available RAM though so that would be a problem.

[Tursi]

You do, but only BEFORE a program is loaded, you can't do it (non-trivally) inside of a BASIC program. You could probably write a little assembly stub to set it up and chain. A secondary issue (not affecting most projects today) is that an unexpanded console can't PEEK and POKE at all, and normal XB can't PEEK or POKE to VDP memory. Again, as long as you have 32k, a little assembly stub can help with that.

[JamesD]

You do, but only BEFORE a program is loaded, you can't do it (non-trivally) inside of a BASIC program. You could probably write a little assembly stub to set it up and chain. A secondary issue (not affecting most projects today) is that an unexpanded console can't PEEK and POKE at all, and normal XB can't PEEK or POKE to VDP memory. Again, as long as you have 32k, a little assembly stub can help with that.

Yeah, you would need to be able to PEEK and POKE to modify the values. I guess VPEEK and VPOKE might be the better way to put it.

 

[+Lee Stewart]

Yeah, you would need to be able to PEEK and POKE to modify the values. I guess VPEEK and VPOKE might be the better way to put it.

 

 

FYI—In XB, we only have PEEK and LOAD (“POKE”). As @Tursi said, we need 32KiB expansion to do it in TI Basic. Actually, with the E/A cartridge (or equivalent ALC loaded by TI Basic) we have PEEKV and POKEV for VRAM in addition to PEEK and LOAD.

 

...lee

[Tursi]

 

FYI—In XB, we only have PEEK and LOAD (“POKE”). As @Tursi said, we need 32KiB expansion to do it in TI Basic. Actually, with the E/A cartridge (or equivalent ALC loaded by TI Basic) we have PEEKV and POKEV for VRAM in addition to PEEK and LOAD.

 

...lee

 

You need 32k expansion to do it in XB. TI BASIC can't PEEK and POKE without Editor/Assembler or MIniMemory (and possibly other carts) /and/ 32k. (But yes, E/A adds POKEV and PEEKV, and XB doesn't have VDP access built in either way.)

[RXB]

RXB and other updated XB's have POKEV and PEEKV and POKEG and PEEKG but RXB also has CALL MOVES(any memory type, # of Bytes,FROM ADDRESS, TO ADDRESS)

 

XB3 has CALL MOVE but can not move from or into strings like RXB can do. CALL MOVES(any memory type,# Bytes,FROM ADDRESS, to String Variable)

 

RXB also has CALL POKER(value,VDP Register) and CALL IO(CRU byte,CRU ADDRESS) and CALL EXECUTE(CPU ASSEMBlY ADDRESS)

Edited April 8, 2015 by RXB

[JamesD]

Well, whatever version of BASIC is required... you need to figure out what addresses to modify to reserve memory to store the data at or how to temporarily hide/un-hide the variable data.
If the start address of where variables is stored is fixed in ROM/GROM and can't be modified in RAM, then you may be out of luck.