Proposed Additions to the PDP-11 Instruction Set: PI Punch Invalid POPI Punch Operator Immediately PVLC Punch Variable Length Card RASC Read And Shred Card RPM Read Programmers Mind RSSC reduce speed, step carefully (for improved accuracy) RTAB Rewind tape and break RWDSK rewind disk RWOC Read Writing On Card SCRBL scribble to disk - faster than a write SLC Search for Lost Chord SPSW Scramble Program Status Word SRSD Seek Record and Scar Disk STROM Store in Read Only Memory TDB Transfer and Drop Bit WBT Water Binary Tree