IBM and Remington Rand electric typewriters were the leading models until IBM introduced the IBM Selectric typewriter in 1961, which replaced the typebars with a spherical element (or typeball) slightly larger than a golf ball, with reverse-image letters molded into its surface. The Selectric used a system of latches, metal tapes, and pulleys driven by an electric motor to rotate the ball into the correct position and then strike it against the ribbon and platen. The typeball moved laterally in front of the paper instead of the former platen-carrying carriage moving the paper across a stationary print position. IBM Selectric II (dual Latin/Hebrew typeball and keyboard)
Selectric II dual Latin/Hebrew Hadar typeball

Replaceable IBM typeballs with clip, 2 Euro coin for scale

The typeball design had many advantages, especially the elimination of "jams" (when more than one key was struck at once and the typebars became entangled) and in the ability to change the typeball, allowing multiple fonts to be used in a single document. Selectric mechanisms were widely incorporated into computer terminals in the 1960s, as they possessed obvious advantages:

The mechanism was reasonably fast and jam-free
It could produce high quality output compared to competitors such as Teletype machines
It could be initiated by a short, low-force mechanical action
It did not require the movement of a heavy "type basket" to shift between lower- and upper-case
It did not require the platen roller assembly to move from side to side (a problem with continuous-feed paper)

The IBM 2741 terminal was a popular example of a Selectric-based computer terminal, and similar mechanisms were employed as the console devices for many IBM System/360 computers. These mechanisms used "ruggedized" designs compared to those in standard commercial typewriters.

IBM also gained an advantage by marketing more heavily to schools than did Remington, with the idea that students who learned to type on an IBM Electric would later choose IBM typewriters over the competition in the workplace as businesses replaced their old manual models.[citation needed]

Later models of IBM Executives and Selectrics replaced inked fabric ribbons with "carbon film" ribbons that had a dry black or colored powder on a clear plastic tape. These could be used only once, but later models used a cartridge that was simple to replace. A side effect of this technology was that the text typed on the machine could be easily read from the used ribbon, raising issues where the machines were used for preparing classified documents (ribbons had to be accounted for to ensure that typists didn't carry them from the facility).[8] Composer output showing Roman, Bold and Italic fonts available by changing the type ball

A variation known as "Correcting Selectrics" introduced a correction feature, where a sticky tape in front of the carbon film ribbon could remove the black-powdered image of a typed character, eliminating the need for little bottles of white dab-on correction fluid and for hard erasers that could tear the paper. These machines also introduced selectable "pitch" so that the typewriter could be switched between pica type(10 characters per inch) and elite type (12 per inch), even within one document. Even so, all Selectrics were monospaced-each character and letterspace was allotted the same width on the page, from a capital "W" to a period. Although IBM had produced a successful typebar-based machine with three levels of proportional spacing, called the IBM Executive, no proportionally spaced Selectric office typewriter was ever introduced. There were, however, two other machines with fully proportional spacing: the expensive Selectric Composer, which was capable of right-margin justification and was considered a typesetting machine rather than a typewriter, and the more reasonably-priced IBM Electronic Typewriter 50, which was capable of proportional spacing but not right-justifying. By 1970, as offset printing began to replace letterpress printing, the Composer would be adapted as the output unit for a typesetting system. The system included a computer-driven input station to capture the key strokes on magnetic tape and insert the operator's format commands, and a Composer unit to read the tape and produce the formatted text for photo reproduction.

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