cmd and powershell

in windows os
how to set cmd environment variable？

set fff = 1

how to set environment variable in powershell?

$env:RUST_BACKTRACE = "1"

how to output all environment variable into console in powershell?

gci Env:

how to output all environment variable into console in cmd?

set

the mothods bellow just make environment variable live in one powershell or cmd ？ when you close it. they will be destroied。