A screenplay goes, often in a standardized format, which boils down to something very simple: one page = 1 minute.
A script page contains: numbers, title and details of scenes, stage directions (directions of what is happening), and dialogues. The presentation is traditionally very light, and the time of reading is approximately one minute.
So, playing time = movie time. So, reading the script, we “feel” the rhythm of the film.
Even the presentation, layout, meets the criteria very standardized. One could rightly criticize the standardization and qualify brake creativity. But really, I do not think, I think this is just a technical framework. Just as a film to be seen, regardless of its originality, must always be on a standard medium projection scenario follows the same logic. This is a technical document supporting a film project.
So often, the scenario is not sufficient to describe and prepare the film. There is only one element among others, and an element whose main purpose is dramatic.
So, before the existence of screenwriting software, we used Word, spending a lot of time to make nice indentation, margins, fat and other characters, so the scenario is the “head” of this standardization. We lost a lot of time. For example, if you wanted to add or remove a scene, it was necessary, manually change all the numbers in the following scenes.
So, use a scriptwriting software saves valuable time for the formatting of the technical document. This is his main interest. Second, some programs allow to go further, to work the “dramatic arc” of the movie, build the characters, to prepare the work plan, etc.. These are additional features, which then can lend more easily to criticism.
A scenario is divided into three “styles” of characters and key paragraphs :
Previously, it was necessary element by element, manually reset the margins, fat, etc.. at each location of the scenario. Now you can use the “styles” in computer science: like piece of text “Dialogues” on calls, and it can be done using a single key, and automatically adjust the margins. If, at some point, we find that the margins of the dialogues are to change, simply change their definition, and everything will change automatically in the document.
The principle styles, ie a semantic approach to text portions, is the basis, inter alia, screenwriting software.
The earlier, seems to me, is Final Draft. Software purely technical shaping the final document.
Then, in the late 90s, Michel Loulergue (writer of “Box Negroes Street”), developed with his company Creative Valley, Scenario Pro software, based on the method of teaching scenario. This is a series of questions posed to the author, to be answered, and that takes, gradually building the structure of the story and characters. An interesting approach to teaching, but has not found its audience, despite partnerships with schools like Esra.
Today, the rule is rather to advice from experts in software, a kind of improved traditional help file.
It is not intended to be exhaustive, but to provide useful tools.