A program called PerfectIt is an "MS Word add-in that helps professionals to proofread faster".
[3] Some plaintext editors, such as Emacs and vi, originally relied on double-spacing to recognize sentence boundaries.
By default, Emacs will not break a line at a single space preceded by a period, but this behavior is configurable (with the option sentence-end-double-space).
[5] This convention originally comes from the underlying SGML standard, which collapses multiple spaces because of the clear division between content and layout information.
To specify and allow multiple spaces to be rendered without collapsing in a web browser, the HTML
tag or CSS white-space property can be employed.ASCII and similar early character encodings provide only a single space, which is breaking and fixed-width (the particular width specified by the respective font).
Non-browser applications that use HTML encoding will not necessarily behave this way at display-time, e.g., later versions of Microsoft Word.