Mazovia encoding

Mazovia encoding is a character set used under DOS to represent Polish text. The character set derives from code page 437, with specific positions modified to accommodate Polish letters. Notably, the Mazovia encoding maintains the block graphic characters from code page 437, distinguishing it from IBM's later official Central European code page 852, which failed to preserve all block graphics, leading to incorrect display in programs such as Norton Commander.

The Mazovia encoding was designed in 1984 by Jan Klimowicz of IMM. It was designed as part of a project to develop and produce a Polish IBM PC clone codenamed "Mazovia 1016". The code page was specifically optimized for the peripheral devices commonly used with the Mazovia 1016 computer, including a graphics card with dual switchable graphics, a keyboard with US English and Russian layouts, and printers with Polish fonts. The Mazovia encoding gained widespread acceptance and distribution in Poland when the Polish National Bank (NBP) adopted it as a standard in 1986. The NBP played a significant role in facilitating the production of compatible computers by Ipaco, which utilized Taiwanese components under the guidance of Zbigniew Jakubas and Krzysztof Sochacki.

Some ambiguity exists in the official code page assignment for the Mazovia encoding:

PTS-DOS and S/DOS support this encoding under code page 667 (CP667).[1] The same encoding was also called code page 991 (CP991) in some Polish software,[nb 1] however, the FreeDOS implementation of code page 991 seems not to be identical to this original encoding. The DOS code page switching file NECPINW.CPI for NEC Pinwriters supports the Mazovia encoding under both code pages 667 and 991.[1] FreeDOS has meanwhile introduced support for the original Mazovia encoding under code page 790 (CP790) as well. The Fujitsu DL6400 (Pro) / DL6600 (Pro) printers support the Mazovia encoding as well.[2] This encoding is known as code page 3843 in Star printers.