Using STD_INPUT and STD_OUTPUT within ModelSim

The standard VHDL'87 TextIO package contains the following file declarations:

file input: TEXT is in "STD_INPUT";
file output: TEXT is out "STD_OUTPUT"; 

The standard VHDL'93 TextIO package contains these file declarations:

file input: TEXT open read_mode is "STD_INPUT";
file output: TEXT open write_mode is "STD_OUTPUT";  

STD_INPUT is a file_logical_name that refers to characters that are entered interactively from the keyboard, and STD_OUTPUT refers to text that is displayed on the screen.

In ModelSim, reading from the STD_INPUT file allows you to enter text into the current buffer from a prompt in the Main window. The last line written to the STD_OUTPUT file appears at the prompt.

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