Definition of keyboard for English Language Learners. : 1  a row or set of keys that are pushed to play a musical instrument (such as a piano) : 2  a musical instrument that is played by means of a keyboard like that of a piano and that produces sounds electronically. : 3  the set of keys that are used for a computer or typewriter.
Classless Inter-Domain Routing (CIDR, pronunciation: /ËsaÉªdÉr/ or /ËsÉªdÉr/) is a method for allocating IP addresses and IP routing. The Internet Engineering Task Force introduced CIDR in 1993 to replace the previous addressing architecture of classful network design in the Internet.
CIDR is a new addressing scheme for the Internet which allows for more efficient allocation of IP addresses than the old Class A, B, and C address scheme. With a new network being connected to the Internet every 30 minutes the Internet was faced with two critical problems: Running out of IP addresses.