A computer has an input / output system called "Teletype", consisting of a keyboard and a text-only printer. Until the 1960s, the teleprinter was an important way of interacting with computers: essentially, it was like the current command line interface (of which it is the ancestor) but instead of having a monitor, still too expensive, there was the printer. Not surprisingly, in Linux the "terminals" are indicated with tty (from teletype, in fact). Teletypewriters were also used to transmit messages remotely, but this use will not be considered here. The teleprinter has the following registers: INPR: 8-bit Input Register OUTR: Output Register, 8 bit FGI: Input Flag, 1 bit FGO: Output Flag, 1 bit IEN: Interrupt Enable, 1 bit The teleprinter knows how to encode the key on the keyboard in ASCII code (8 bit), and can also decode (for printing). When a value is loaded into INPR (read from the keyboard), FGI is immediately set. When the printing of a character on the printer is completed, FGO is set. Describe how the CPU can interact with the teleprinter, using first only the first 4 registers, then also the last one. The interactions must be of the type: "read a character from the keyboard", "print a character", "read a character from the keyboard and print it at the same time". Show that, using the last flag, implementation is more efficient.

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