.
            .
         CALL  IGWASYS,(RC1,RS1,CODE1,LEVEL,ATTR)   Test pre-DFSMS/MVS
         LTR   R15,R15        Test return code
         BNZ   BADSYS
         CLC   LEVEL,=F'2'      Test for MVS/XA DFP Version 2
         BE    OLDSYS
         MVC   SYSNAME,UNKNAME  Assume name is unknown
         BL    BADSYS           Branch if unknown system
         MVC   SYSNAME,=CL12'MVS/DFP'   Show we are on MVS/DFP
         CLC   LEVEL+12(4),=F'1'        See if after MVS/DFP
         BL    SHOWSYS           Branch if before DFSMS/MVS
         CALL  IGWASYS,(RC1,RS1,CODE2,LEVEL,ATTR)
         LTR   R15,R15          Branch if environment or
         BNZ   BADSYS             system error
         MVC   SYSNAME,UNKNAME      Assume unknown product name
         CLC   LEVEL+12(4),=F'1'    Test for DFSMS/MVS code
         BL    OLDSYS           Branch if unexpected code
         MVC   SYSNAME,=CL12'DFSMS/MVS'  Show product name
         BE    SHOWSYS         Branch if DFSMS/MVS
         MVC   SysName,=CL12'OS/390 DFSMS'  Set assumed new name
         CLC   LEVEL+12(4),=F'3'    Branch if
         BL    SHOWSYS                OS/390
         BH    COPYSYS              Branch if after z/OS name
         MVC   SysName,=CL12'z/OS DFSMS'  Assume early z/OS
*  On z/OS.  Test for early releases.
         CLC   Level(8),=F'1,3'     Branch if
         BL    ShowSys                before z/OS 1.3
*  On z/OS 1.3 or later.  Use the name provided by the system.
CopySys  L     R14,16               Point to CVT
         L     R15,CVTDFA-CVT(,R14) Point to DFA
         L     R14,DFAELNMP-DFA(,R15) Point to element name
         USING DFAELNM,R14
         MVI   SysName,C' '         Blank out name
         MVC   SysName+1(L'SysName-1),SysName
         LH    R15,DFAELNML         Get name length
         CH    R15,MaxLen           Skip one instruction if
         BNH   *+8                    name not too long
         LH    R15,MaxLen           Truncate to our field length
         BCTR  R15,0                Decrement for EX instruction
         EX    R15,MVCName          Copy name from DFA
         DROP  R14
ShowSys  EQU   *     Handle version, release and modification level
         .
         .
RC1      DC    F'0'    Return code
RS1      DC    F'0'    Reason code
CODE1    DC    F'1'    Ask for pre-DFSMS DFP level
CODE2    DC    F'2'    Ask for level of DFSMS, or later
LEVEL    DC    4F'0'   Version, release, Modification Level and code
ATTR     DC    4F'0'   SMS attributes
SYSNAME  DC    CL12'MVS/XA DFP'  Name of product
UNKNAME  DC    (L'SYSNAME)C'?'   Constant for unknown name
MaxLen   DC    Y(L'SysName)      Our maximum allowed length of name
MVCName  MVC   SysName(0),DFAELTXT-DFAELNM(R14)