Sometimes you need to enter a negated operator like ≠. If you’re a C/C++ programmer, you might think that != should map to ≠, since that’s what != means in those languages (and some others). But since in mathematics ! means factorial, this choice is a bad idea for inputting ≠ into mathematical text. You can type in \ne to get ≠, but there’s the simpler combination: /=. In the linear format used in Microsoft Office math, / is used for “stacked” fractions. But /= building up to a fraction with an empty denominator followed by an equal sign isn’t very useful. Also if you really want such a fraction, you can get it by typing /<space>.

Accordingly in Office 2010 math entry, /= builds up to ≠. This approach can be used to input many other negated operators as listed in the following table

All of these operators are in the U+2200 Unicode block (Mathematical Operators) except for the ASCII characters <, =, and >. TeX has a similar, but more verbose approach that uses the control word \not followed by the name of the operator. For example, in TeX, \not\exists produces ∄.

Note that if you don’t like an automatic translation when entering math, you can undo the translation by typing ctrl+z. This way of entering negated operators along with some other extensions to the linear format will be documented in a future version of Unicode Technical Note #28.