The kind of company may be a factor in whether you find it in a given directory.
If you do not find a large company in a directory, it may be private; many directories include only public companies. Another possibility is that the company you are looking for is a subsidiary, or smaller branch, of a larger company. A to Z Databases indicates ownership structure in a business description under Corp. Family Tree.
In this Guide, you will be using business directories. These directories use a system of number codes, in systems called SIC and NAICS, to arrange businesses by type, so the user can find, for example, all the manufacturers of communications equipment.
These numbers are explained in this short video:
Many business directories have a look-up feature or cheat sheet that lets you find a code that will represent the type of business you're looking for. Here are some other places to search by key words to find an appropriate code: