IBM 1401 assembly code to print a Christmas card

card.s

               job  card.s
               ctl  6641
               org  087
     X1        dcw  000  * Index 1, pointer to text
               dc   00
               org  333
     start     sw   1
               sbr  x1, buf+80
     rloop     r                   * Read cards into page buffer
               bce  rhs, 1, -
               mcw  80, 0&x1       * Copy card image to page buffer
               bce  write, 1, $    * Stop reading when $ card reached, start printing
               sbr  x1, 132&x1     * Advance x1
               b    rloop          * Read next card
     rhs       cs   1
               sw   1
               mcw  80, 66&x1      * Move card image to right half of page buffer
               sbr  x1, 132&x1
               b    rloop
     write     sbr  x1, buf        *   Print buffer
               sw   201
     wloop     mcw  132&x1, 332    * Load card into 201 to 332
               bce  done, 201, $
               w
               sbr  x1, 132&x1
               b    wloop          * Loop
     done      cc   1              * eject page
               h                   * Halt: print again if start pushed
               b    write
     
     buf       equ  1000
               end  start