text: // System call numbers
  #define SYS_fork          1
  #define SYS_exit          2
  #define SYS_wait          3
  #define SYS_pipe          4
  #define SYS_sem_alloc     5
  #define SYS_read          6 
  #define SYS_kill          7 
  #define SYS_exec          8 
  #define SYS_fstat         9 
  #define SYS_chdir        10 
  #define SYS_dup          11 
  #define SYS_getpid       12 
  #define SYS_sbrk         13 
  #define SYS_sleep        14 
  #define SYS_uptime       15
                          
  #define SYS_sem_init     16 
  #define SYS_sem_destroy  17 
  #define SYS_sem_wait     18 
  #define SYS_sem_post     19  
                         
  #define SYS_open         20 
  #define SYS_write        21 
  #define SYS_mknod        22 
  #define SYS_unlink       23 
  #define SYS_link         24 
  #define SYS_mkdir        25 
  #define SYS_close        26
  