Mainframe: IBM z/Architecture series using BAL Hello World Example

HELLO    CSECT               The name of this program is 'HELLO'
         USING *,12          Tell assembler what register we are using
         SAVE (14,12)        Save registers
         LR    12,15         Use Register 12 for this program  
         WTO   'Hello, world!' Write To Operator
         RETURN (14,12)      Return to calling party
         END  HELLO          This is the end of the program