SHELL

upgrade composer version

composer self-update

upgrade to composer 2 windows

If going from version 1 to 2 use composer self-update --2

upgrade composer

 To update composer command just find location of composer.phar and update as:
 where composer 	#Retrieves you location of your composer.phar
 cd path_to_composer.phar #Move to directory with composer.phar
 php composer.phar self-update	#Update your composer