Comparison Flags

The Comparison Flags are contained within the processor COM and OVF flags two-digit field. This field is defined as:

Information Digit Bit
Reserved 01) 3
Reserved 2
Reserved 1
Reserved 0
Reserved 1 3
Overflow Flag 2
Comparison Low (COML) flag 1
Comparison High (COMH) flag 0

The states of the Comparison Flags are:

COML COMH State
0 0 Null (Clear)
0 1 Greater or High
1 0 Less or Low
1 1 Equal

The Comparison Flags will be stored in memory and reset by the Branch Communicate (OP = 30), Enter (OP = 31), Virtual Enter (OP = 35), and Hyper Call (OP = 62) instructions. They are also stored in memory and reset by the Interrupt and Hardware Call procedures.

The Comparison Flags are unconditionally restored from memory by the Return (OP = 63) and Virtual Branch Reinstate (OP = 93) instructions and conditionally restored from memory by the Exit (OP = 32) instruction.

1) Digit 0 is used as a flag during the Exit and Return instructions to specify whether to restore the setting of the Overflow and Comparision flags