Data-in-virtual sample program code (continued)

For both the set and display requests, the program displays the character at the specified location. For an invalid request, the program displays an error message. For all requests, the program then goes to process another statement.

When requested to terminate, the program saves any changes in the linear data set, terminates its use of the object (using UNIDENTIFY), and returns to the operating system.

LGOODINP EQU   *
         MVC   M1A,VCARDA          Address changed/displayed
         MVC   M1B,VCARDV          Storage value
         CLI   M1B,X'00'           If X'00' (untouched),
         BNE   LGOODIN1            * change to "?".
         MVI   M1B,C'?'            *
LGOODIN1 LA    R2,M1               R2 -> message to print
         B     LTELL               Go tell user status
LINVFUNC LA    R2,M2               Unknown function
         B     LTELL               Go tell user status
LINVADDV LA    R2,M3               Invalid address
         B     LTELL               Go tell user status
LINVADDR LA    R2,M4               Address out of range
LTELL    EQU   *                   R2 -> message to print
         LA    R4,L31B03           Return to L31B03 in 31-bit mode
         LA    R1,L24B03           Go to L24B03 in 24-bit mode
         BSM   R4,R1               R4 = A(X'80000000'+L31B03)
L24B03   PUT   VSYSPRT,(R2)        Print the message
         BSM   0,R4                Return to 31-bit mode at next instr
L31B03   B     LREAD               Continue
* End-of-file on SYSIN, or "E" function requested.
* Save any changes (DIV SAVE). Then issue UNIDENTIFY, which internally
* issues UNMAP and UNIDENTIFY.
LCLOSE   EQU   *
         CLI   VSWUPDT,0           Any updates outstanding ?
         BE    LCLOSE1             * No -- skip SAVE
         DIV   SAVE,ID=VTOKEN      Save any changes
         LA    R2,5                Error code from SAVE
         LTR   R15,R15             SAVE ok ?
         BNZ   LERROR              * No -- quit
LCLOSE1  DIV   UNIDENTIFY,ID=VTOKEN All done with object
         LA    R2,6                Error code from UNIDENTIFY
         LTR   R15,R15             UNIDENTIFY ok ?
         BNZ   LERROR              * No -- quit
         L     R13,4(,R13)         Unchain save areas and return
         LM    R14,R12,12(R13)     *
         SR    R15,R15             *
         BR    R14                 *
LERROR   ABEND (R2),DUMP           Take a dump