1. A process for extracting the source operand data for a floating point calculation from program code stored in tangible media for a computer system, comprising the steps of: invoking said program code, containing a plurality of instructions including millicoded instructions, said program code including a millicode program instruction for passing instruction text from said program code to cause a millicode entry, and entering from said millicode entry control information into a millicode routine and for setting register tags in a floating point register control unit, and executing said millicode routine and passing therein to an extract floating point register indirect (EXFDI) instruction for extracting for a floating point calculation through register indirect addressing contents of a floating point register array and for writing said contents of the floating point register array to a millicode working register.