Tip of the month from PRC May 1996 

Numbering chapters & sections

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Tip of the month is edited by Peter Ring, PRC (Peter Ring Consultants, Denmark)
- consultants on how to write user friendly manuals 

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New edition: 17 March 1997

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Why do we number chapters and sections hierarchically?

Exceptions from the general rules: New!

• A (specified) numbering system is demanded by law or a standard. Justified or not in the individual case - you have got to follow it!
• In electronic documents, all internal references can and should be made with hyperlinks, and this reduces the need for numbering significantly. In general, numbers in electronic documents are justified only if the text is ...
• the electronic version of a paper document with numbers.
• there is a law or a standard to be followed demanding numbers.
• there is a need for external non-electronic cross-references to/from the document.

Disadvantages of numbering chapters and sections hierarchically

For the users:

• It is more difficult to find a section number than a page number. The reason is that all pages have the same thickness, chapters and sections don't! To compensate for that, you must have page numbers anyway - and what does the user then need the section numbers for?
• Chapter and section numbers makes the product and the manual look more complicated and technical, especially to non-technicians. This reduces the use of the manual, which most often means, that the user use less of the features of the product.
• In some manuals, especially short manuals, it is an unnecessary noise.

• The numbers takes up space on the always too short heading lines.
• Many users are irritated because they find it easier to find page 234 than to find section 2.3.4. This irritation may be transferred to their general satisfaction with the product.

Advantages of numbering chapters and sections hierarchically - and when to do it

For the users:

• In case a large manual is expected to be updated regularly, e.g. in a ring binder, it is a lot easier to use numbered chapters + chapter related page numbers. This is especially the case if the user writes personal notes in the manual, and consequently want to keep most pages intact. (Thanks to John Bell, Cornerstone Technologies, Inc., for this point). Only in this case the page numbering should preferably be "chapter-number - chapter-page" instead of consecutive page numbers. (Thanks to Joe Sokohl, Campbell Software, Inc. for this point).
• In case one user works with many manuals with identical chapter and section numbers, it is easier to find a specific subject. You then know, e.g., that the generators are always described in section 2.4. That is mainly the case with big, very technical service manuals for "much alike" products, e.g., service manuals for car engines or airplane jet engines. But the user of a video machine doesn't benefit the same way!
• In case there are many sections on a page, the reference to a low level section number is more precise than a page number. On the other hand, this tempts the writer to use a high number of levels, and that is generally bad, see " rules and tips " below.
• It makes it easier for the user to see which level in the hierarchy the heading is. True, especially in the past where manuals were typewritten. Today there are so many other ways like font size, underling, boxes, etc., so that's not a valid reason any longer. On the contrary, it tempts the writer to use the same font for all headings, and that's bad!

For the techwriters:

• In case a large manual is expected to be updated regularly, e.g. in a ring binder, it is easier to keep track of the updates. Fortunately there is a user interest here, too, see above.
• If section numbers are demanded by the customer or an authority like the FDA, then you have got to do it.
• In case the product is tailor made from more or less standardized parts, it is a convenience for the editor of the manual to be able to choose between different versions of section 1.2.3, 1.2.4, etc., and in that way make sure it is all there. But in may cases you can easily do without it (e.g., with numbered file names only), and unless the user belongs to one of the two first user advantages above, (s)he doesn't care. But it is acceptable if you need to number Figures and/or Tables relative to the section because the section structure is variable.
• It is easier to make references if the page numbers can differ from version to version. But with today's "bookmark" reference system, that's no problem anymore!

Rules and tips for numbering of chapters and sections

• Number chapters and sections only if ...
• The individual user typically works with many manuals with identical chapter and section numbers.
• You need to number Figures or Tables relative to the chapter because the section structure is variable. This is not either wanted or unwanted by the users, but it is often very practical for the editor.
• There are many sections on a page AND many references to the lowest level sections.
• Chapter and section numbers are demanded by the customer or an authority like the FDA.
• Never use more than 2 to 3 levels. Have you ever tried to look for section 4.12.6.1.13? Cover the number withy a finger and tell where that section is placed relative to section 4.12.7.6.9? It is simply too many digits to have in the head combined with all these decimal points. The U.S. Army recommends not more than 2 levels (but at least 6 levels has been seen!).
• Use numbers only, not letters or mixtures like 6.G.e. You don't win anything except the extra character above 9 (J instead of 10, etc.). But most people find it much easier to look for a number in a numbered list than to look for a letter in an alphabetic list. They have to think if G is before or after H.
• Tip: Use TAB instead of space between the number and the text. That makes it easier to automatically generate a nice looking list of contents.
• Tip: Do not use a point after the last digit. Then you will never run into problems like "see section 1.2. Fig. 12 ...". Or that half the sections has points after and the other half of them has not! No point after the last digit is the recommendation of ISO 2145.

If you disagree with these ideas - or have more relevant points +/-, please e-mail me !
(Ideas for "Tip of the month" subjects are welcome, too!)

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