*        String prepend - 14/04/2020
PREPEND  CSECT
         USING  PREPEND,13         base register
         B      72(15)             skip savearea
         DC     17F'0'             savearea
         SAVE   (14,12)            save previous context
         ST     13,4(15)           link backward
         ST     15,8(13)           link forward
         LR     13,15              set addressability
         MVC    C+L'B(L'A),A       c=a
         MVC    C(L'B),B           c=b+c  (prepend)
         XPRNT  C,L'C              print buffer
         L      13,4(0,13)         restore previous savearea pointer
         RETURN (14,12),RC=0       restore registers from calling sav
A        DC     C'world!'          a
B        DC     C'Hello '          b
C        DC     CL80' '            c
         END    PREPEND