A TTY (i.e. TeleTYpewriter) is a special device that lets people who are deaf, hard of hearing, or speech-impaired use the telephone to communicate, by allowing them to type text messages. A TTY is required at both ends of the conversation in order to communicate.
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TTY is terminal which is used to type text message.
Shell :the outside protective covering part of a seed i.e. kernel.
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framework or exterior structure to central or essential part of a system.
Console means the keyboard and monitor physically attachements to a computer.