Inverter output square wave safe for computing

I am looking at purchasing a 2Kva inverter for my computer, screen & printer. The inverter has a square wave output. For the PC this is probably not a problem as the PC power supply converts to 5V DC. What wouldthe effect of a plain square wave have on the screen and printer though ? Should I even try this ? Doesanyonehave any experience with this?

Is there a standard that defines the shape of the wave used as input to a device? e.g. IEEE "whatever"

Most electronic devices rectify the AC from the mains and charge a capacitor to almost the peak voltage of the sinewave. But the peak voltage of a squarewave inverter is less (0.707 times less) than the peak voltage of a sinewave so that the average power into an incandescent light bulb or heater is the same.
An electronic device might not work when the voltage is too low.

A squarewave inverter is cheap so its voltage regulation might be awful then the voltage will be too high with a light load and the voltage will be too low with a heavy load. I can hear my computer drawing more current when it thinks hard because then its fans speed up. When it is idling then it draws less current and its fans slow down. I don`t want its supply voltage to go up and down.

The answer is easy for classical non-PFC SMPS. They can work well with squra wave inverters, but the voltage should be near to the peak value of the regular sine voltage, e.g. 300 V for 230 VAC or 150V for 115 VAC. SMPS have a considerable input regulation range, so the value isn't critical. Many SMPS even work with DC input voltage of the same magnitude.

Newer SMPS with PFC input stage may have problems with square wave input.

ALL depends. Most equipment works alright. Some don't. No way to tell until you try.