groff: Tab Stops
5.1.4 Tab Stops
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'gtroff' translates "tabulator characters", also called "tabs" (normally
code point ASCII '0x09' or EBCDIC '0x05'), in the input into movements
to the next tabulator stop. These tab stops are initially located every
half inch across the page. Using this, simple tables can be made
easily. However, it can often be deceptive as the appearance (and
width) of the text on a terminal and the results from 'gtroff' can vary
greatly.
Also, a possible sticking point is that lines beginning with tab
characters are still filled, again producing unexpected results. For
example, the following input
1 2 3
4 5
produces
1 2 3 4 5
⇒Tabs and Fields.