When the target key-token CV is null
When you use any of the LEFT, BOTH, or RIGHT keywords, and when the control vector in the target key token is null (all B'0'), bit 3 in byte 59 will be set to B'1' to indicate this is a double-length DATA key.
When you use any of the LEFT, BOTH, or RIGHT keywords, and when the control vector in the target key token is null (all B'0'), bit 3 in byte 59 will be set to B'1' to indicate this is a double-length DATA key.