Write a simple single thread CSC4420 shell , i.e., no concurrent commands, to support at least the following built-in commands:

• prompt can set to any string you input, in addition to the current history event number, i.e, %h as in csh;
• url : list the course web site
• hour : list class times
• room : list classroom location
• desp : list the description of this course
• text : list the textbook
• ref : list the reference books
• prof : list the professor's name
• pol : professor's office location
• poh : professor's office hours
• pma : professor's email address
• ta : list the TA's name
• tol : TA's office location
• toh : TA's office hours
• tma : TA's email address
• history : list history of events up to the number you set
• help : list all the available commands
• exit or quit : exit CSC4420 shell