How have printers and screens changed from the first computer to the computers used today?
The first computer printers were often offline electromechanical devices, the computer either punched the printout on cards or wrote it to a magnetic tape. The cards or tape were then read by the printer. Many different printer mechanisms were used (e.g. vertical sliding print bars impact line printer, spinning drum impact line printer, flying spot CRT photographic page printer [the photographs had to be developed in a darkroom], automatic electric typewriter impact character printer) often adapted from those used on the electromechanical punchcard unit record equipment of the time. A typical printer could weigh up to one ton. Printing was usually done one sided on long continuous feed fanfold tractor feed paper. The photographic page printers printed on very wide rolls of photographic film.
Modern computer printers are almost always directly connected to the computer (e.g. USB) or are shared network devices (e.g. Ethernet, Wi-Fi). The computer typically sends a Postscript file to the printer. The printer contains an embedded microcomputer to receive and queue up these files, then manage the printer mechanism to print them. Most printers today use one of two nonimpact printing mechanisms: inkjet (shoots tiny drops of colored ink onto the paper) or laser (derived from the Xerox photocopier mechanism). A typical inkjet printer can weigh as little as 10 pounds. A typical laser printer weighs from about 30 pounds to a couple hundred pounds depending on features included. Printing is usually done on individual sheets of ordinary paper and can often be done double sided.
The first computers did not usually use screens or monitors.
Computer monitors first came into common usage on the timesharing minicomputer systems of the 1960s as a replacement for teletypes (they were commonly called "glass teletypes") to save on the costs of paper. With the introduction of microprocessors in the 1970s these computer terminals became "smart terminals" that could do various display formatting operations automatically. These used heavy CRTs.
Many modern computers often have a built in screen making an external computer monitor unnecessary. The early built in screens used CRTs but as liquid crystal and LED flat panel displays were developed they replaced CRTs and have now become universal. Laptops and "all in one computers" have a screen built in, while tablet computers and smartphones are built around the screen and often look like that is all there is to the device.