In a standard-conforming procedure the floating-point registers are used as shown in Table 2-2.
Table 2-2 Floating-Point Register Usage
| Register | Usage |
| F0 | Floating-point function value register. In a standard call that returns a floating-point result in a register, this register is used to return the real part of the result. In a standard call, this register may be modified by the called procedure without being saved and restored. |
| F1 | Floating-point function value register. In a standard call that returns a complex floating-point result in registers, this register is used to return the imaginary part of the result. In a standard call, this register may be modified by the called procedure without being saved and restored. |
| F2..F9 | Conventional saved registers. If a standard-conforming procedure modifies one of these registers, it must save and restore it. |
| F10..F15 | Conventional scratch registers. In a standard call, may be modified by the called procedure without being saved and restored. |
| F16..F21 | Argument registers. In a standard call, up to six floating-point arguments may be passed by value in these registers. In a standard call, these registers may be modified by the called procedure without being saved and restored. |
| F22..F30 | Conventional scratch registers. In a standard call, these registers may be modified by the called procedure without being saved and restored. |
| F31 | ReadAsZero/Sink. Hardware defined: binary zero as a source operand, sink (no effect) as a result operand. |