member('BACKER')
drvfree function(drive)  ! returns a real

irg group,pre(in)
al    byte
ah    byte
bl    byte
bh    byte
cl    byte
ch    byte
dl    byte
dh    byte
si    ushort
di    ushort
cflg  ushort
flag  ushort
  .

org group,pre(out)
ax    ushort
bx    ushort
cx    ushort
dx    ushort
si    ushort
di    ushort
cflg  ushort
flag  ushort
  .

srg  group,pre(s)
es   ushort
cs   ushort
ss   ushort
ds   ushort
      .

intnum  short
ret  short
frees  real

drivelet  string(1)
drivenum  byte

RootPath    CSTRING(4)
Sectors     ULONG
Bytes    ULONG
FreeClusters    ULONG
TotalClusters   ULONG

    code
    OMIT('***',_WIDTH32_)
    drivelet = upper(drive)
    drivenum = val(drivelet) - 64
    if drivenum > 26 then return(0).

    intnum = 021h
    in:ah = 036h
    in:dl = drivenum
    ret = int86x(intnum,irg,org,srg)
    frees = out:ax * out:bx * out:cx
***
    COMPILE('***',_WIDTH32_)
    drivelet = upper(drive)
    RootPath=drivelet & ':\'
    GetDiskFreeSpaceA(RootPath,Sectors,Bytes,FreeClusters,TotalClusters)
    frees=Sectors * FreeClusters * Bytes

***
    return(frees)