Screenwriting

According to BARRY PEARSON, A WRITER/PRODUCER IN THE FILM AND TELEVISION INDUSTRY, in a nutshell:

The NOVEL. Its CONDUIT is the written word.
Its DOMINANT STORYTELLING MODE is the printed page.
Its MOST POWERFUL CREATOR is the author
The STAGE PLAY.Its CONDUIT is the live theater production.
Its DOMINANT STORYTELLING MODE is the spoken word.
Its MOST POWERFUL CREATOR is the playwright.
The SCREENPLAY.Its CONDUIT is the movie production.
Its DOMINANT STORYTELLING MODE is directions and actor dialogue.
Its MOST POWERFUL CREATOR (Screenwriter is not the creator of the finished work. He or she is the creator of the plan for the other creators).
The MOVIE.Its CONDUIT is the movie theater screen.
Its DOMINANT STORYTELLING MODE is the projected image.
Its MOST POWERFUL CREATOR is the director.

Screenwriting in Context

A screenplay is the script or the blueprint exclusive for producing visual arts as film and television. Screenwriting is the process of writing a screenplay.
Screenplays are dominated by images. Screenwriting divides the story into scenes while playwright breaks it down into acts.
Script writing is the process of writing dialogue which can be used in talk shows, news programs, sports broadcasts and infotainment(magazine style) programs. Script writing doesn't involve discussing the visuals of a TV show or a movie. This is a more specific type of script writing which is called screenwriting.
Screenwriting is also a process of writing a script, but this is only used for filmmaking.Screenwriting provides the visuals that complement what the characters are doing and saying. 

Writting your Screenplay

Keep in mind that a screenplay is visual and your characters' actions move the story forward from scene to scene. Actions show the audience what it needs to know. Seeing a character do something is far more powerful than having him or her talk about it.
A scene is a unit of action. In each scene, define who (character or characters), what (situation), when (time of day), where (place of action), and why (purpose of the action).

Scene Headings: Each time your characters move to a different setting, a new scene heading is required.

Scene headings are typed on one line with some words abbreviated and all words capitalized.

Example: A scene set inside a hospital emergency room at night would have the following heading:

INT. HOSPITAL EMERGENCY ROOM - NIGHT

Interior is always abbreviated INT. and exterior is abbreviated EXT. A small dash (hyphen on your keyboard) separates the location of the scene from the time of day. Leave a two-line space following the scene heading before writing your scene description. Names of characters are displayed in all capital letters the first time they are used in a description, and these names always use all capital letters in a dialogue heading. Example: CATHY sits at the end of the first row of plastic chairs. Her head is bent over, and she stares intently at the floor. The names of characters who have no dialogue are not capitalized when mentioned in scene descriptions. Example: A man moans softly as he presses a bloody gauze pad against his forehead. A woman cradles a listless infant in her arms. Sounds the audience will hear are capitalized (eg: STORM ROAR or CAR WHISTLE). Sounds made by characters are not considered sound cues and do not require capitalization." Dialogue is centered on the page under the character's name, which is always in all capital letters when used as a dialogue heading. If you describe the way a character looks or speaks before the dialogue begins or as it begins, this is typed below the character's name in parentheses. Example: DOCTOR (apologetically) We did everything possible.

Here is an example of a complete scene in the screenplay format:

INT. HOSPITAL EMERGENCY ROOM - NIGHT

A crowded hospital emergency waiting room. Clean but cheerless.

Sick and injured people sit in plastic chairs lined up in rows. A TV mounted near the ceiling BLARES a sitcom. No one is watching.

A man moans softly as he presses a bloody gauze pad against his forehead. A woman cradles a listless infant in her arms.

CATHY sits at the end of the first row of plastic chairs. Her head is bent over, and she stares intently at the floor.

She raises her head slowly, brushes her long, silky hair away from her face.

We see fear in her eyes as they focus on a clock that hangs above the front desk. She twists a tissue between her fingers and is unaware that bits of it are falling on the floor.

The door to the emergency treatment room opens, and a middle-aged DOCTOR dressed in hospital green walks through the door toward Cathy, who bolts out of the chair and hurries toward him.

DOCTOR (apologetically) We did everything possible.

CATHY (gasps) What are you saying?

DOCTOR I'm sorry…

CATHY (screaming) No!

All eyes in the waiting room are riveted on Cathy and the Doctor. Cathy lunges at the Doctor, beating her fists against his chest.

CATHY (CONT'D) (shouting) You killed him!

Our scene ends here with Cathy's last words, but it could continue with more dialogue and action. Note that (CONT'D), the abbreviation for continued, is added in parentheses next to Cathy's name above. CONT'D is added here because Cathy has just spoken and is continuing to speak. Her dialogue was interrupted by a description of other actions, not by another character's dialogue.