Looks like what he really wants is to use Ada which has had much better support for low-level programming than C.
Example:
Word : constant := 4; -- storage element is byte, 4 bytes per word
type State is (A,M,W,P); type Mode is (Fix, Dec, Exp, Signif);
type Byte_Mask is array (0..7) of Boolean; type State_Mask is array (State) of Boolean; type Mode_Mask is array (Mode) of Boolean;
type Program_Status_Word is record System_Mask : Byte_Mask;
Protection_Key : Integer range 0 .. 3;
Machine_State : State_Mask;
Interrupt_Cause : Interruption_Code;
Ilc : Integer range 0 .. 3;
Cc : Integer range 0 .. 3;
Program_Mask : Mode_Mask;
Inst_Address : Address;
end record;
for Program_Status_Word use
record
System_Mask at 0*Word range 0 .. 7;
Protection_Key at 0*Word range 10 .. 11; -- bits 8,9 unused
Machine_State at 0*Word range 12 .. 15;
Interrupt_Cause at 0*Word range 16 .. 31;
Ilc at 1*Word range 0 .. 1; -- second word
Cc at 1*Word range 2 .. 3;
Program_Mask at 1*Word range 4 .. 7;
Inst_Address at 1*Word range 8 .. 31;
end record;
for Program_Status_Word'Size use 8*System.Storage_Unit;
for Program_Status_Word'Alignment use 8;