The existence of shells is linked to the very existence of IT. At the time, all coders agreed that communicating with a computer using aligned 1/0 switches was seriously irritating. It was only logical that they came up with the idea to communicate with a computer using interactive lines of commands in a language somewhat close to english.

make

• echo with option -n
• cd with only a relative or absolute path
• pwd with no options
• export with no options
• unset with no options
• env with no options or arguments
• exit with no options
• ’ inhibit all interpretation of a sequence of characters.
• " inhibit all interpretation of a sequence of characters except for $.
• '<' redirect input.
• '>' redirect output
• '>>' redirect output with append mode.
• Pipes | The output of each command in the pipeline is connected via a pipe to the input of the next command.
• Environment variables ($ followed by characters) expand to their values
• $? expand to the exit status of the most recently executed foreground pipeline.
• ctrl-C ctrl-D ctrl-\ work like in bash.
• Historic of commands implemented with termcaps
• Search and launch the right executable (based on the PATH variable or by using relative or absolute path)