Editing Intel 8085 (section)

====Undocumented instructions====
A number of undocumented instructions and flags were discovered by two software engineers, Wolfgang Dehnhardt and Villy M. Sorensen in the process of developing an 8085 assembler. These instructions use 16-bit operands and include indirect loading and storing of a word, a subtraction, a shift, a rotate, and offset operations.<ref>{{cite journal
 | first1 = Wolfgang
 | last1 = Dehnhardt
 | first2 = Villy
 | last2 = M. Sorensen
 | title = Unspecified 8085 op codes enhance programming
 | journal = Electronics
 | publisher = McGraw-Hill
 | date = January 1979
 | pages = 144–145
 | issn = 0013-5070
 | url = http://www.club100.org/memfiles/index.php?action=downloadfile&filename=UnDoc85.pdf&directory=Steve%20Adolph/undocumented_8085_opcodes
}}</ref>

By the time 8085 was designed but not yet announced, many designers found it to be inferior to the competing products already on the market. The next generation 16-bit 8086 CPU was already in development. Intel made a last minute decision to leave 10 out of 12 new 8085 instructions undocumented to speed up and simplify the design of the upcoming 8086 CPU.<ref>
{{cite journal
 | first1 = Stanley
 | last1 = Mazor
 | title = Intel's 8086
 | journal = IEEE Annals of the History of Computing
 | publisher = IEEE Computer Society
 | date = January–March 2010
 | volume = 32
 | pages = 75–79
 | doi = 10.1109/MAHC.2010.22
 | issn = 1058-6180
 | url = https://ieeexplore.ieee.org/document/5430762
}}
</ref>