Is a Computer Just a Calculator? Understanding How It Works (Documents, Images, Music, Movies, Chat, Photos…)

 

1. A Computer Is an Electrically Powered Calculator

In the previous post, I mentioned that “a computer is essentially a calculator that runs on electricity.” Of course, we don’t use computers just for arithmetic. We write documents, draw pictures, listen to music, watch movies, chat online, and edit photos.

So how can a “calculator” do all these different things?
The secret is simple: everything can be turned into numbers.

2. The Basic Principle

  • First, convert all kinds of information into numbers.

  • Next, process those numbers using a set procedure (an algorithm).

  • Finally, convert the results back into something humans can sense (a monitor, printer, speaker, etc.).

For example, when you press A on your keyboard, what really goes into the computer isn’t the shape of the letter, but the number 65, the ASCII code for “A.”

👉 I even made a small ASCII Code Lookup Tool where you can type a character and see its code.


  • Uppercase A = decimal 65, hex 41.

  • Hangul (Korean) characters follow a similar principle, built from combinations of basic symbols mapped to numbers

3. Everything Becomes Numbers



  • Text: Each character is stored as a numeric code (like ASCII).

  • Images: Think of your screen as a grid of tiny squares (pixels). Each pixel is just three numbers—red, green, and blue brightness, each ranging from 0 to 255. For example, a resolution of 1920 × 1080 means your screen has 2,073,600 pixels (Full HD).

  • Sound: Recorded as rapid samples of air vibrations, stored as a long list of numbers.

  • Video: Simply a sequence of images (frames) shown in rapid order, combined with sound numbers.

Once text, images, audio, and video are expressed as numbers, a computer can process them all by calculation.

4. Why Computers Are Calculators

“Calculation” isn’t something mystical. It’s just repeating small, simple operations extremely fast and accurately:
addition, subtraction, multiplication, division, comparison, copying, branching, and so on.

  • Photo editing: “Increase brightness by 20%” = multiply each pixel’s RGB values by 1.2, capped at 255.

  • Word processing: Spell-check underlines = split words, compare with a dictionary, then draw red pixels under missing words.

  • Video playback: Decode compressed numbers into frames and sync them with sound numbers.

5. Example: Typing “A” on the Keyboard

  1. The keyboard sends a signal when a key is pressed.

  2. The computer interprets it as “this is A” and converts it to the number 65.

  3. That number goes to the current input box (like Notepad).

  4. The font system finds the shape for “A” and maps it to pixels.

  5. The system calculates the color of each pixel and displays it on the screen.

All of this happens in less than 1/60 of a second—so fast that it feels instantaneous.

6. Programs Make the Difference

Since letters, pictures, sound, and video are all just numbers, the same hardware can perform completely different tasks depending on the program:

  • A photo editor repeatedly adjusts pixel numbers.

  • A music app calculates and outputs sound numbers.

  • A spreadsheet rapidly adds, compares, and rearranges table numbers.

This is why a “calculator” can become a word processor, a movie player, or even an AI chatbot—simply by running different instructions on the same underlying machine.

Wrapping Up

Now you know why a computer is often described as a calculator at its core. By turning the world into numbers and processing them at incredible speed, it can take on an endless variety of roles.

Thanks for reading, and I’ll see you again in the next post!


You can view the original Korean blog post at the link below

View in Korean

Location: 대한민국 서울특별시

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