Retro1.org codex

ATTN                                                     CP Privilege Class:  G

Use the ATTN command to make an attention interruption pending at your virtual
console.  The format of the ATTN command is:
+----------+------------------------------------------------------------------+
| ATTN     |                                                                  |
+----------+------------------------------------------------------------------+


Usage notes:

1.  The REQUEST command performs the same function as ATTN; the two commands
    can be used interchangeably.

2.  The BEGIN command is not required after you issue ATTN.

3.  CP ignores the ATTN and REQUEST commands if an I/O operation is in progress
    at the console or if other interrupts are pending for your virtual machine.
    This condition may result if you issue the ATTN or REQUEST command from a
    program by means of DIAGNOSE X'8'.