Having covered nearly all the previous sciences, we now find ourselves faced with this one; programming! This is where we find that when you encode a letter or character or symbol into a page of text, it will place an image to the physical devices where the charge will be released based on the shape of the symbol. That means the shape of the character will be like a photograph, and, the effect on the 'tape' will be one where the image overlaps the reel to form a image of condensed energy, in form of a charge of electricity where the two meet, releasing a charge of energy equal in joules to the shape of the character. Basically, it is like playing electrician with the keyboard, encoding the message in electricity for the computer to relay over the bus to all connected devices, which are made of further circuits to enact the devices to function in various ways.
This is how computers work, historically speaking, of course.