Anybody familiars with the old DOS-apps?

[AbsolutFDM]

Hi everyone,

I just came across an old DOS-apps program written in C. Screenshot of the program is attached.
Anyway, It has two so-called textboxes, which will take 2 string inputs (one for username, and the other one for password). Each input is at most 8 characters, so when you enter the first textbox with 8 chars already, the cursor will sit still and the program does not response to additional keyboard input, except for backspace (delete the character) and enter (go to the second textbox).
The second textbox behaves the same, except when you click enter, it will try to match username and password you have just filled.

I'm just curious how to draw all the graphics, and do the "limiting input" to only 8 characters.

Thanks ppl!

[CornedBee]

The drawing could probably be done with good usage of colored text. The other thing could be done with a keyboard interrupt handler (a function that gets called every time a key is pressed)