The computer keyboard is based on the typewriter invented by Christopher Latham Sholes in Milwaukee, Wisconsin. Sholes's first typewriters, patented in 1868 by Sholes, Carlos Glidden, and Samuel W. Soulé, featured a keyboard with keys arranged in alphabetical order. The machine lacked a shift key and typed only in capital letters. Although typists found the alphabetical arrangement advantageous for finding the correct keys, it had two primary disadvantages. First, the letters used most often were not easily reached. Second, when typists hit a series of neighboring keys in rapid succession, such as R-S-T, the typewriter bars would jam, requiring the typist to stop and untangle them. Sholes developed the QWERTY keyboard in 1872 to resolve both problems. It is still the standard layout because millions of typists are trained in its use.