PTR   EQU 11B
      ORG 100B
      CLC 0        Turn off all devices
START STC PTR,C    Set I/O control bit
WAIT  SFS PTR      Skip if control bit is set
      JMP WAIT     Loop till ready
      LIA PTR      Read one char
      OTA 1        Write to S
*      HLT 0        Halt so we can see the char
      INB          Increment B as a counter
      JMP START