'****************************************************************************
'
'   Environment ver„ndern / Modify the environment
'   fr/for  PowerBASIC 3.0/3.2
'
'   Frei Kopierbar / Public Domain
'
'   entwickelt von / developed by   :  Thomas Gohel
'                           Fido    :  Thomas Gohel@2:2410/330.1
'                           InterNet:  author@pbsound.snafu.de
'                           Homepage:  http://www.snafu.de/~pbsound/
'
'****************************************************************************

$ERROR NUMERIC OFF

CLS
ENVIRON "PROMPT="               ' kill the old prompt
AddEnviron("PROMPT=This is a demo for a new: " + CHR$(13,10) +"[PowerBASIC-SHELL] $p$g")
SHELL                           ' demonstration
END

FUNCTION AddEnviron(Update$) public
        LOCAL PSPAdresse??, MemorySeg??, Mem16??, MemoryRest??
        Carry% = 0

        ' *** Adresse des PSP ermitteln / Find the PSP ***
        ! mov ax, &h6200
        ! int &h21
        ! mov PSPAdresse??, bx
        DEF SEG = PSPAdresse??
        DEF SEG = CVI(PEEK$(&h2c,2))

        ' *** Environment holen / Read environment ***
        FOR i% = 0 TO 1024
            IF PEEK$(i%, 2) = CHR$(0,0) THEN EXIT FOR
        NEXT i%

        ' *** Environment modifizieren / modify ***
        OldEnv$ = PEEK$(0,i%)
        NewEnv$ = OldEnv$ + CHR$(0) + Update$

        ' *** Holen des Programmnamen/pfad / Read Programname/path ***
        z% = i%
        Programmpath$ = ""
        FOR i% = z% TO 1024
            IF PEEK$(i%, 4) = CHR$(0,0,1,0) THEN EXIT FOR
        NEXT i%
        WHILE PEEK(i% + 4) <> 0
            Programmpath$ = Programmpath$ + CHR$(PEEK(i% + 4))
            INCR i%
        WEND

        ' *** Enviroment fertigstellen / Create new environment ***
        NewEnv$ = NewEnv$ + CHR$(0,0,1,0) + Programmpath$ + CHR$(0)

        ' *** DOS-Speicher anfordern / Alloc DOS-Memory ***
        Mem16?? = CEIL(LEN(NewEnv$)/16)
	x& = SETMEM(-(Mem16??*16)-16)
        ! mov ax, &h4800
        ! mov bx, Mem16??
        ! int &h21
        ! mov MemorySeg??, ax
        ! mov MemoryRest??, bx
        ! jnc MemoryOk
        Carry% = 1
        MemoryOk:
        IF Carry% = 0 THEN

            ' *** Schreiben des Environment in den DOS-Speicher ***
            DEF SEG = MemorySeg??
            POKE$ 0, NewEnv$

            ' *** Patchen des PSP / Patch the PSP ***
            DEF SEG = PSPAdresse??
            POKEI &h2c, MemorySeg??
            DEF SEG
        ELSE
            BEEP
            PRINT "Ups??? nur:"; MemoryRest??*16; "Byte verfgbar"
        END IF
END FUNCTION