about subdomain and robots

should i copy robots to all subdomains?

[webon]

hello, currently , i am setting up my server. and i would like to have 2 subdomain
names, which is mean

1. www.domainname.com

2. kw1.domainname.com

3. kw1.domainname.com

but my question here is what is different between

www.domainname.com/kw1/ and kw1.domainname.com?

the second one will take more advanatage from that?

and usually i put the robots.txt under the root directory,
but if i have the subdomain, do i need to also copy the same
robots.txt file to different root?

thanks

[jdMorgan]

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