A feature of specialized texts is that often occur in them duplication of fragments. It can be single words, phrases and even whole sentences. When repetition happens, a natural course of action is to copy the earlier translation in a new place. You can do this manually, but it is better to automate this process. That is the purpose of programs supporting translation, i.e. CAT-s (computer assisted translation). These tools record text typed by the translator and associate it with the source text. In this way, a database containing pairs of translation units is created (mostly whole sentences) in two languages. When in a text appear a sentence that was once translated, such program insert it automatically saving the translator's work.
There are many CAT programs. All work more or less according to the principles described above, but of course may differ in detail and offered functions. For example some programs, such as Wordfast, are called overlays for Microsoft Word editor, while others, such as Trados, may work as overlay, but also offer self-editors (eg. TagEditor). The most popular CAT tools include SDL Trados, Wordfast (previously free), Déjà Vu and OmegaT (free). Obviously this is not an exhaustive list.
The general principles of these programs will be presented on the example of OmegaT software.
Before starting work, we have to realize that CAT programs do not perform translations, but only substitute longer passages of text previously translated by an interpreter. Therefore, this activities should not be referred to as machine translation, because in fact a man does the translation and these programs serve only as a support tool, like a word processor or a computer dictionary.