In the early days of computer optical character recognition

Optical character recognition

Optical character recognition, usually abbreviated to OCR, is the mechanical or electronic translation of scanned images of handwritten, typewritten or printed text into machine-encoded text. It is widely used to convert books and documents into electronic files, to computerize a record-keeping...

, there was a need for a font that
could be recognized by the computers of that day, and by
humans. The resulting compromise
was the OCR-A font, which used simple, thick strokes to form recognizable
characters.
The font

Font

In typography, a font is traditionally defined as a quantity of sorts composing a complete character set of a single size and style of a particular typeface...

 is
monospaced (fixed-width), with the printer required to place glyphs  cm ( inch) apart, and the reader
required to accept any spacing between  cm ( inch) and  cm ( inch).
The OCR-A font was standardized by the American National Standards Institute

American National Standards Institute

The American National Standards Institute is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organization also coordinates U.S. standards with international...

 (ANSI)
as X3.4-1977.