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  1. I am learning some basics in computer. In that in ASCII I read if 65 is A .
  2. When we pressing key A what is happening next? Is the electric signal is passing as on & off & reaching to decimal part 65 (or) directly converted to binary?
  3. If it is reaching 65 then which location character map (or) encoding is available?

Please clarify. I have more questions in computer basics. I want to understand computer basics.

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    $\begingroup$ Hello kaviyarasu. Cs.stackexchange.com is for theoretical computer science, you question is possibly more suited under stackoverflow.com. $\endgroup$
    – Chaos
    Aug 6, 2021 at 12:59
  • $\begingroup$ oh ok . i will ask there. thank you. $\endgroup$
    – kaviyarasu
    Aug 6, 2021 at 14:42
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    $\begingroup$ I actually think that stackoverflow doesn't suit this question better. I would say this question is somewhere between CS and electrical engineering $\endgroup$
    – nir shahar
    Aug 6, 2021 at 15:04

3 Answers 3

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Your keyboard isn't going to send anything indicating the letter "a". It will send for example that the second key in the fourth row of my keyboard has been pressed.

Your keyboard is most likely connected through USB. Part of the USB standard is describing how a USB device identifies itself as a keyboard, and how a USB keyboard tells the device on the other end what keys were pressed. It will also tell the computer the physical layout of the keys.

The operating system on your computer will take multiple bits of information: What physical keyboard layout, what keyboard language the user has chosen (if the language is set to French, a different key is used for the letter a), what other keys are pressed at the same time (shift, shift-lock, control, option, command, function), what keys have been pressed before (pressing the "a" key together with the shift-key after pressing option and "u" will create a letter "Ä" on my computer).

Oh, by the way, "Ä" is not an ASCII character. And there are letters like ®†¥øπ etc.

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  • $\begingroup$ Hi, nice explanation, where can i find & read these type of topics ? so i can understand more. $\endgroup$
    – kaviyarasu
    Jan 6, 2022 at 13:05
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Everything always works in binary. ASCII, is just a way to interpret the binary into letters and numbers.

The decimal part of ascii (such as the value $65$ being equivalent to $a$) is just for the purpose of human readability, since binary isn't as natural to humans as decimal numbers

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  • $\begingroup$ thank you for clarifying . $\endgroup$
    – kaviyarasu
    Aug 6, 2021 at 15:43
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The basic element of computing machines as we know them, is an array of binary digits - a series of 0s or 1s. These binary digit arrays are the only symbols that a general purpose computer is capable of storing or processing at the hardware level.

All of us are presumably familiar with decimal numbers and with mathematical operations done in decimal. Implementing the mechanics of the decimal system using binary is relatively straightforward.

The problem is that working consistently in binary - inputting binary on keyboards, and reading binary on display screens - is not convenient for the human users of computers.

A computer is efficient at working with just two digits - 0 and 1 - in a variety of sequential configurations. Humans prefer to work with a wider variety of characters in much shorter sequences, and binary is very inefficient to process by any other means than a computer.

The question then is how you represent a wider variety of characters, such as those we use for natural language, and also decimal digits, using a computer?

The answer is that native binary symbols are assigned to represent characters on a fairly arbitrary basis.

Using the ASCII encoding, the native symbol 1000001 (which rendered as a decimal number would be 65) is assigned to represent the character A.

When you press A on the keyboard, the native symbol 1000001 is submitted to and stored by the computer. And when the computer stores 1000001 in the video memory on a text-based terminal, the display renders that native symbol back out to the screen as character A.

Similarly, for a printer like a dot-matrix or a daisy-wheel, sending the symbol 1000001 causes them to imprint the pattern, or strike the character, of A.

By being consistent at all times, end-to-end, the user never sees any native binary symbols - he simply reads and writes in the characters he is familiar with.

For graphical (non-text based) interfaces and modern printers, the actual process is somewhat more complicated, involving many more layers of translation. But the essential situation is still the same - you press A on the keyboard and that will likely find its way into main memory (or disk storage) represented natively as 1000001. And when the same symbol is displayed or printed, it's translated back into a visual representation of the character A.

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