text: // System call numbers
  #define SYS_fork    1
  #define SYS_exit    SYS_fork+1
  #define SYS_wait    SYS_exit+1
  #define SYS_pipe    SYS_wait+1
  #define SYS_read    SYS_pipe+1
  #define SYS_kill    SYS_read+1
  #define SYS_exec    SYS_kill+1
  #define SYS_fstat   SYS_exec+1
  #define SYS_chdir   SYS_fstat+1
  #define SYS_dup     SYS_chdir+1
  #define SYS_getpid  SYS_dup+1
  #define SYS_sbrk    SYS_getpid+1
  #define SYS_sleep   SYS_sbrk+1
  #define SYS_uptime  SYS_sleep+1
  #define SYS_open    SYS_uptime+1
  #define SYS_write   SYS_open+1
  #define SYS_mknod   SYS_write+1
  #define SYS_unlink  SYS_mknod+1
  #define SYS_link    SYS_unlink+1
  #define SYS_mkdir   SYS_link+1
  #define SYS_close   SYS_mkdir+1
  #define SYS_halt    SYS_close+1
  // student system calls begin here. Follow the existing pattern.
  // p1-06
  #define SYS_date    SYS_halt+1
  // p2-04
  #define SYS_getuid    SYS_date+1
  #define SYS_getgid    SYS_getuid+1
  #define SYS_getppid   SYS_getgid+1
  
  #define SYS_setuid    SYS_getppid+1
  #define SYS_setgid    SYS_setuid+1
  //p2-21
  #define SYS_getprocs  SYS_setgid+1
  
  // p4
  #define SYS_getPriority SYS_getprocs+1
  #define SYS_setPriority SYS_getPriority+1 
  
  // p5
  #define SYS_chmod SYS_setPriority+1 
  #define SYS_chown SYS_chmod+1 
  #define SYS_chgrp SYS_chown+1
  
   
  