Bit# 15 14 13 12 11 10 09 08  07 06 05 04 03 02 01 00
      |  |  |  |  |  |  |  |   |  |  |  |  |  |  |  |
     X7 X6 X5 X4 X3 X2 X1 X0  CD S6 S5 S4 S3 S2 S1 S0
      |                        |  |
      +-- exit code (8bit)     |  +-- signal code (7bit)  
                               |
                               +-- core-dumped flag