Final answer:
The key combination [Ctrl]+[Alt]+ does not have a universal action assigned to it in Windows computers. It may perform a specific function in certain applications, such as switching focus in virtual machine software.
Step-by-step explanation:
When you press [Ctrl]+[Alt]+ on a Windows computer, typically no action is predefined for this specific key combination, and it would not display anything. It's possible you might be referring to a certain program or virtual machine that has programmed a special function for this key combination. For example, in some virtual machine software, specific key combinations can be used to change the focus between the host and the virtual machine. However, the key combination you mentioned is not universally recognized as a shortcut in Windows or most applications. In the context of the figure, you referenced about the Bulletin Board System from the 1980s, the key combination might have had a special function within that specific system or software.