UNIT NAME:  SYSTEM

      REMARKS:  The System unit is Turbo Pascal's run-time library.  It
                implements lowlevel routines for features such as I/O,
                String handling, overlay management, 8087 emulation, and
                other functions not handled by other units.

    CONSTANTS:

       Const
          OvrCodeLst  : Word = 0;        (* Overlay code segment list   *)
          OvrHeapSize : Word = 0;        (* Initial overlay buffer size *)
          OvrDebugPtr : Pointer = nil;   (* Overlay dubugger hook       *)
          OvrHeapOrg  : Word = 0;        (* Overlay buffer origin       *)
          OvrHeapPtr  : Word = 0;        (* Overlay buffer pointer      *)
          OvrHeapEnd  : Word = 0;        (* Overlay buffer end          *)
          OvrLoadList : Word = 0;        (* Loaded overlays list        *)
          OvrDosHandle: Word = 0;        (* Overlay DOS handle          *)
          OvrEmsHandle: Word = 0;        (* Overlay EMS handle          *)
          HeapOrg     : Pointer = nil;   (* Heap origin                 *)
          HeapPtr     : Pointer = nil;   (* Heap pointer                *)
          FreePtr     : Pointer = nil;   (* Free list pointer           *)
          FreeMin     : Word = 0;        (* Minimum free list size      *)
          HeapError   : Pointer = nil;   (* Heap error function         *)
          ExitProc    : Pointer = nil;   (* Exit procedure              *)
          ExitCode    : Integer = 0;     (* Exit code                   *)
          ErrorAddr   : Pointer = nil;   (* Run-time error address      *)
          PrefixSeg   : Word = 0;        (* Program segment prefix      *)
          StackLimit  : Word = 0;        (* Stack pointer low limit     *)
          InOutRes    : Integer = 0;     (* I/O result buffer           *)
          RandSeed    : LongInt = 0;     (* Random seed                 *)
          FileMode    : Byte = 2;        (* File open mode              *)
          Test8087    : Byte = 0;        (* 8087 test result            *)


         VARS:

       Var
          Input     : Text;              (* Input standard file  *)
          Output    : Text;              (* Output standard file *)
          SaveInt00 : Text;              (* Saved Interrupt $00  *)
          SaveInt02 : Text;              (* Saved Interrupt $02  *)
          SaveInt1B : Text;              (* Saved Interrupt $1B  *)
          SaveInt23 : Text;              (* Saved Interrupt $23  *)
          SaveInt24 : Text;              (* Saved Interrupt $24  *)
          SaveInt34 : Text;              (* Saved Interrupt $34  *)
          SaveInt35 : Text;              (* Saved Interrupt $35  *)
          SaveInt36 : Text;              (* Saved Interrupt $36  *)
          SaveInt37 : Text;              (* Saved Interrupt $37  *)
          SaveInt38 : Text;              (* Saved Interrupt $38  *)
          SaveInt39 : Text;              (* Saved Interrupt $39  *)
          SaveInt3A : Text;              (* Saved Interrupt $3A  *)
          SaveInt3B : Text;              (* Saved Interrupt $3B  *)
          SaveInt3C : Text;              (* Saved Interrupt $3C  *)
          SaveInt3D : Text;              (* Saved Interrupt $3D  *)
          SaveInt3E : Text;              (* Saved Interrupt $3E  *)
          SaveInt3F : Text;              (* Saved Interrupt $3F  *)
          SaveInt75 : Text;              (* Saved Interrupt $75  *)