Are you YELLING at me? Are YOU yelling at ME?
Like boldface or italics, all caps in small doses lend emphasis. They're great for book covers and road signs but considered rude in email. Selectively equating all caps with shouting long predates the Internet. (“This time he shouted it out in capital letters.” Evening Star, Feb. 28, 1856.) There’s method in the madness.
ALL CAPS go back to the ancient Romans, who used capital letters only. Early medieval scribes invented cursive and lower-case scripts for faster copying. The printing press standardized a mix of caps and lower case, with two advantages over boxy all caps. First, mixed case took less space and used less paper. Second, in long texts with high resolution, it’s easier to read. The variety of letter shapes, some dropping below the line and others rising high above it, helps the eyes distinguish whole words at a time.
Later technologies offered less choice of fonts and cases. Teletype equipment was engineered with a single all-caps keyboard; traces remain in military, naval, and weather communications. Typewriters produced upper and lower case but not bold or italics, making capitalization the way to accentuate key words in legal documents. Ever wonder what's behind the tradition of all caps for comics? Hand lettering, ink that bleeds on cheap paper, short phrases—and smaller speech bubbles because no letters drop below the line.
I'm a historian who writes novels and literary nonfiction. My home base is Madison, Wisconsin.