I've always wondered how Opening Titles and End Credits in the movies were created before Computers existed?
Usually, if we talk about credits without any movie scene in the background, it was done by using a long sheet of paper or plastic or other material they want with credits written on it. Artists used different type of fonts and texts as required. Then this sheet is rolled in front of a camera where it is recorded and added into the movie.
They also used various types of fonts and color themes to convey the genre and/or subject of the movie in the title cards.
If we talk about the credits with some movie scene running in the background, it was done using an Optical Printer. This is also used in layering for special effects in old era.
An optical printer is a device consisting of one or more film projectors mechanically linked to a movie camera. It allows filmmakers to re-photograph one or more strips of film. The optical printer is used for making special effects for motion pictures, or for copying and restoring old film material.
Common optical effects include fade outs and fade ins, dissolves, slow motion, fast motion, and matte work. More complicated work can involve dozens of elements, all combined into a single scene.
From this Canva article,
film titles – the graphic image or sequence at the opening of a movie – were simply hand-illustrated cards photographed and inserted into a film. Today, they are much like a mini-movie showcases the art of graphic design with filmmaking.
Adding to A J's very good answer:
Multiple exposure of the film can do the trick without using anything digital.
Double exposure of the negative
In the first step, the motion picture is taken. Then the masked text, or text annimation, os taken as a second exposure resulting in overexposed (bright white) letters and properly exposed scene behind.
Double exposure of the positive
In the first step the motion picture is taken and developped. After the photocopy of the negative the film is exposed again through masked text (animation) resulting in overexposed (black) letters and properly developped scene behind.