OCR, Optical Character Recognition, software requires a scanning device. Text on a page scanned into the computer. The scanned image is at this point a 'graphic' image. The OCR software checks the images against a built in dictionary to find the closed matches to the shape of the character or letter. At a very high speed, it then assigns the matching computer code and continues until finished.
OCR is available for many languages and is even available on handheld devices connected or separate from the computer.