How to copy files in /Applications/* using Terminal? # whoami
root

# pwd
/Applications/Calendar.app/Contents/MacOS

# cp Calendar Calendar.backup
cp: Calendar.backup: Operation not permitted


im curious to know why im not able to copy applications from a root terminal using the cp command?

sh-3.2# system_profiler SPSoftwareDataType 
Software:
System Software Overview:

  System Version: macOS 10.13.4 (17E199)
  Kernel Version: Darwin 17.5.0
  Boot Volume: lily
  Boot Mode: Normal
  Computer Name: lily’s MacBook Air
  User Name: System Administrator (root)
  Secure Virtual Memory: Enabled
  System Integrity Protection: Enabled
  Time since boot: 2:03
Applications that come preinstalled with macOS are protected by SIP.  The Calendar App, being preinstalled falls under this category.  Firefox, for example, wouldn't.

So, anything in 


/Applications/Calendar/..... is protected
/Applications/3rdPartyApp/.... is not



  System Integrity Protection restricts the root user account and limits the actions that the root user can perform on protected parts of the Mac operating system.