I remember walking around a trade show in the early 80's and doing something similar. It was a "HP Microwave Symposium" and aside from lots of good talks and papers, the exhibit hall had lots of high dollar HP (later Agilent/Keysight) RF test equipment. One of the items on display was a HP8566 spectrum analyzer which had a (primitive by today's standards, but) "smart" display capable of drawing vector graphics, time-linear graphs, and text. After using one on my own for a while, I had become curious about the display so I had learned everything that I could about it. So down on the exhibit hall floor, I walked up to the instrument while the sales guy was proclaiming how great it was (which was true) and I entered eight lines of code (about 30 keystrokes). Then I pressed the button to view trace C (which most people still don't know about) and up popped a rolling blinking text display of my name. Most of the people nearby were impressed, but since the instrument was no longer displaying the RF spectrum that the sales guy was talking about, he said; "I know how to fix that." Then he walked over and pressed the green "Instrument Preset" button, which the HP documentation said would always restore the instrument to a known starting point. When the display did not change, the sales guy yelled at me; "WHAT DID YOU DO?!?!?" (My program was in Trace C of display memory, which is not initialized by the Instrument Preset function.) So after watching him panic for a moment, I walked over and swapped traces B&C (shift-key followed by the swap A&B button). Now my program was in trace B (and blanked) so the screen returned to normal. Everyone was relieved! So just before walking away, I swapped my program back into trace C, viewed trace C, and hit the green preset button again. As I walked to the next exhibit, I saw him cycle the AC power to the instrument in frustration.