Thanx you all. I'm beginning to understand a bit....

These are the first 20 lines of the binary-block in the file:
------------------------------------------------------------------------

 1
mogoo mih m o
  1
_ll P/:1 [:,681 ^ 336>1<: ^ \VL ]*63;:- _nk ^ \VL mogqoo QK _mk H:; ^ /- mo mmeogemi monn
  1
n fqfffffffffffffffj:rooh n:rono
  1
>,27:>;:- {rn rn _nm mnmqoqoqjgmm |
  1
=0;& {m rn {rn {l {rn {rn |
  1
-:9@)+r:&:r>++-6= {rn rn {rn {rn {n {k {j |
  1
3*2/ {i rn {rn {rn {h {n |
  1
:&:@-:961:2:1+ {rn rn _j 8-6;  n _l +-6 n _k ,*-9 o _l >;5 o _k 8->; o _f /0,+<7:<4 o _k ,+03 oqoohilhjnjnfgklfljfh _k 1+03 lo _k ;,63 o _g 93>+1:,, o _h /6'>-:> o _k 72>' o _i 8-6;>- o _j 28-6; looo _j *8-6; o _j )8-6; o _no :1;@96:3;, |
  1
):-+:'@+:2/3>+: {rn rn l o n g |
  1
-:9@)+r:&:r>++-6= {rn rn {rn {rn {l {k {j |

-------------------------------------------------------------------------It consists of pairs of lines: the first is a code (always 1), the second is the data. I think that the latter is wrote according to the SAT format (well to the SAB format, it's binary....).

ACIS supports two kinds of save files, SAT and SAB, which stand for °»Standard ACIS Text°…
and °»Standard ACIS Binary°…, respectively. Although one isASCII text and the other is binary
data, the model data information stored in the two formats is identical

A SAB file has a .sab file extension. A SAB file uses delimiters
between elements and binary tags, without additional formatting.
The binary formats supported are:
int . . . . . . . . . . 4--byte 2s complement (as long)
long . . . . . . . . . 4--byte 2s complement
double . . . . . . . 8--byte IEEE
char . . . . . . . . . 1--byte ASCII
where °»byte°… is eight bits, and files are considered to be byte strings. For multi--byte data
items, byte order normally just matches that of the processor being used, but a specific order
may be imposed by compiling with the preprocessor macro BIG_ENDIAN or
LITTLE_ENDIAN defined.