Muz wrote on 2020-01-01, 20:29:

When the computer was invented, how did the computer recognize letters from the input of keyboard and display it into the monitor?

It didn't.

That's a very broad question and makes some presumptions about what a computer is 😀

To simplify an answer, it'll need to be split it into smaller parts:

How did the computer recognize letters from the input of the keyboard

This was a merge of several technologies: first programmable computers needed to take input in some form, and other mechanical and electro-mechanical devices generally took input in the form of punch cards or punch tapes, so it made sense to use it for computers as well. The idea of using punchcards for computer input dates back to XIX century and Babbage's Analytical Engine (punchcards themselves date back to XVIII century). Also in XIX century (only a few years later) telegraph messages were encoded (using keyboards) to punch-tapes. This way of transferring text into computers (keyboard to punch card/tape, then card/tape to the machine) persisted in one way or another into ~1960s-70s.

I'm not sure which proto-computer first used keyboard for direct input - it might've been German Zuse Z3 in 1941 (English Colossus Mk1 from 1943 was "programmed" via plugs, not a keyboard).

From a machine perspective, "a letter" is nothing but a number in some pre-agreed encoding.

… and display it into the monitor?

Various forms of monitor-like output started to appear in 1940s-1950s - at first, usually as outputs for analog (non-digital) computers, often in the form of oscilloscopes, later in the form of vector outputs (displays capable of showing graphics via drawing lines) - as opposed to modern displays, which are almost exclusively raster outputs (draw raws of pixels).

Around 1960s-1970s computers grew powerful enough to support multi-user operating systems (Unix was the first really successful one) - initially in the form of "dumb terminals" consisting of teletypes (basically electro-mechanical typewriters, writing to paper), later as keyboard from teletypes with output printed to the CRT display - so this was the time when something resembling modern keyboard input and output capable of displaying text appeared.

Why punch cards were used? Was the card some sort of paper to recognize the output?

Homework Assignment?

I remember there used to be special OCR fonts that were machine-readable. You couldn't just put any piece of text into the computer.

There was also a special font for magnetic (not optical) text readers. You normally saw this on checks and credit cards.

Muz wrote on 2020-01-01, 23:18:

Why punch cards were used? Was the card some sort of paper to recognize the output?

Because it is really simple technology. Literally just a paper card/tape with holes in it - it's easy to build a machine to write to such tape (keyboard punching holes in the paper) and easy to transform into an electrical signal (a hole in the paper - connection can be formed, meaning '1'; no hole - no connection, '0'). It was originally invented in XVIII century France to control textile machinery.

By the stamps on the back of the envelopes.

PCBONEZ wrote on 2020-01-02, 00:06:

Homework Assignment?

Lolz it wouldn't be the first time Muz needed help with his homework.

So, the CPU was invented after the monitor?

Computers don't have monitors. They reach directly into your brain and make you think they do.