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How Simple On/Off Switches Store the Digital World | Working of Computer Memory — Transcript

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0:00Have you ever wondered how computer
0:02memory actually works? Today, all the
0:04books you could read in your lifetime
0:06can fit into a single tiny memory chip.
0:09And it is not just books, your photos,
0:12music, movies, bank details, even your
0:15passport or medical records. Almost
0:17everything about you now lives in
0:19digital form. But how does this digital
0:22memory really work? We have all heard
0:24that computers use a binary language.
0:27But how can just two numbers 0 and 1
0:30represent such a wide variety of data?
0:33Back in the early days when we tried to
0:35know more about these machines, the only
0:38answers we got were confusing diagrams
0:40and technical terms like CPU, memory
0:43unit and so on. Today everyone carries a
0:46computer in their pocket in the form of
0:48a smartphone. Yet hardly anyone knows
0:51the simple secret behind it all. In this
0:54video, I will break down how computer
0:56memory really works in the simplest way
0:59possible. And by the end, you will see
1:01how the simple idea of on and off builds
1:05our entire digital world.
1:11Hi friends, welcome to a new video on
1:14science simplified for all. We often
1:16hear that computers work using the
1:18binary system. That means a computer has
1:21only two numbers to deal with 0 and one.
1:25Every book, every picture, every song,
1:28every movie stored inside a computer is
1:30represented only by these two numbers 0
1:33and 1. But how does that really happen?
1:36Let us understand this with a simple
1:37example. Imagine you are standing on a
1:40quiet road where not many vehicles pass.
1:43Someone asks you to count how many cars
1:45go by in 1 hour. You cannot just count.
1:48You must also record the number somehow,
1:51but you are not given a notebook or pen.
1:53Instead, you're given four light bulbs,
1:56each with its own switch. You can turn
1:58each bulb on or off whenever you like.
2:02At the end of 1 hour, you must use these
2:04bulbs to show exactly how many cars
2:07passed. You can do this in two ways.
2:10First method, switch on one bulb for the
2:12first car, the second bulb for the
2:14second car, and so on. This works fine,
2:17but only up to four cars. Once all four
2:20bulbs are on, you cannot record anymore.
2:23If a fifth car passes, you have no way
2:26to show it. So, there is a second
2:28method. When the first car goes by, you
2:30switch on the first bulb. When the
2:33second car comes, you switch off the
2:35first bulb and turn on the second. For
2:38the third car, you keep the second bulb
2:40on and also turn on the first again. For
2:43the fourth car, you turn off both the
2:45first and second bulbs and turn on the
2:48third bulb. For the fifth car, you keep
2:50the third bulb on and switch on the
2:53first again. If you continue like this,
2:55only when the 15th car passes will all
2:58four bulbs be on. That means with four
3:01bulbs, you can represent numbers from 0
3:04to 15. In other words, four bulbs with
3:08on and off states can create 16
3:10different combinations. These
3:12combinations are shown in this table.
3:15When all bulbs are off, that represents
3:17zero. When all are on, that represents
3:2015. Any other combination in between
3:24represents a number between 0 and 15.
3:27So, with just four bulbs, you can not
3:29only record the number, but anyone else
3:31looking at the bulbs later can also read
3:34the same number from it. This is very
3:36similar to how a computer's memory
3:38works. We often say that computers use
3:41binary and that memory is stored in
3:43zeros and ones. But in reality, there
3:46are no actual zeros and ones inside the
3:49computer. What exists are only two
3:51states on and off. We call off zero and
3:56on one. In our bulb example earlier, a
3:59glowing bulb can be called one and an
4:02unlit bulb can be called zero. In that
4:05case, this table can also be written in
4:07the form of zeros and ones as shown
4:10here. That is why we call it the binary
4:13system. But remember, at its core, there
4:16are no actual ones and zeros. It is
4:19simply on and off states. In the bulb
4:22example, to read the result, we had to
4:25look with our eyes and see which bulbs
4:27were glowing. But now imagine that
4:30instead of bulbs, we are using devices
4:32called capacitors. Some of you may
4:34already know what a capacitor is. For
4:37those who do not, you just need to
4:39remember this. A capacitor is a tiny
4:42device that can temporarily store a
4:44small amount of electric charge. You can
4:46think of it like a miniature battery.
4:48The difference is that unlike a battery,
4:51a capacitor can charge and discharge
4:53very quickly, though it cannot hold that
4:55charge for long. Now, let us replace the
4:58four bulbs with four capacitors. Instead
5:00of switching on a bulb, we charge a
5:03capacitor. Instead of switching off a
5:06bulb, we discharge it. If all four
5:08capacitors are discharged, that
5:10represents zero. If all four are
5:13charged, that represents 15. The
5:16intermediate states work exactly like
5:18they did in the bulb example. The
5:20advantage now is that we no longer need
5:22to count glowing bulbs with our eyes. We
5:25can simply connect an electrical circuit
5:27and it can detect which capacitors are
5:29charged and which are not. That means
5:32the numbers stored in these capacitors
5:34can be read directly by a circuit. In
5:37short, these capacitors can be used to
5:39store any number between 0 and 15 and we
5:43can read that number whenever needed.
5:45This is in principle how computer memory
5:48stores data. Instead of bulbs, computers
5:51use capacitors. And to control the flow
5:53of charge into and out of a capacitor,
5:56they use electronic switches called
5:58transistors. Instead of the mechanical
6:01switches we used in our example, so the
6:03smallest unit of memory is made up of a
6:06single capacitor and a single
6:08transistor. Millions and millions of
6:10such units are combined to make up
6:12computer memory. In this system, a
6:15charged capacitor is called a one and a
6:18discharged capacitor is called a zero.
6:21This is what we mean when we say
6:23computers use the binary system. The
6:25smallest unit made of one capacitor and
6:28one transistor is called a bit and each
6:30bit can only exist in one of two states
6:34zero or one. If this much is clear, we
6:37can now move to the next stage. Now the
6:40next thing we need to understand is
6:42this. How do different types of data
6:45like text, images and more get stored in
6:48this simple on and off format or in
6:50other words in the binary format of 0
6:53and one. From here on in the video we
6:56will mostly use the terms 0 and one.
6:59Remember one means either a glowing bulb
7:02or a charged capacitor. Zero means
7:05either an unlit bulb or a discharged
7:08capacitor. Keep this picture in mind.
7:11Earlier we saw that with four bulbs we
7:13could form 16 different combinations.
7:16That meant we could represent numbers
7:18from 0 to 15. By the same logic if we
7:22had eight bulbs then 256 different
7:25combinations would be possible. Here is
7:28why a single bulb has two possible
7:30states on or off. With two bulbs the
7:34total combinations are 2 * 2 = 4. With
7:38three bulbs, 2 * 2 * 2 equals 8
7:42combinations. With four bulbs, 2 to the
7:45power of 4, which equals 16
7:47combinations. That is what we saw
7:50earlier. So, continuing this pattern
7:52with eight bulbs, we get 2 to the power
7:55of 8 equals 256 possible combinations.
8:00That means with eight bulbs, we can
8:02represent every number from 0 to 255.
8:06This combination shown here represents
8:09zero and this one represents 255.
8:13All the other states in between
8:15represent the numbers from 1 to 254.
8:19With these 256 combinations, we can
8:22represent everything that qualifies as
8:24text. capital and small English
8:26alphabets, numbers from 0 to 9,
8:29punctuation marks like full stop, comma,
8:31apostrophe and even special characters
8:34such as number sign or asterisk. There
8:36are standard systems for this and one of
8:38the most widely used is called ASI code.
8:42According to ASI, every text character
8:44and symbol is assigned a unique code
8:47between 0 and 255.
8:50The table that lists all these codes is
8:52called the ASKI table. For example, the
8:55capital letter A has an ASKI code of 65.
8:59If you open a word file, hold the Alt
9:02key and type 65, the letter A will
9:05appear on the screen. In this way, every
9:08character in the table can be typed
9:10using its ASI code. Each ASKI code also
9:13has a corresponding binary code. For the
9:16letter A, the ASKI code is 65 and this
9:19is its binary form. When you type A on
9:22the keyboard, what actually happens
9:24inside the computer's memory is that
9:26eight capacitors switch to a particular
9:29onoff pattern that represents this
9:31binary number. That on and off state of
9:34the capacitors is what becomes the
9:36computer's version of the letter A. So
9:38to represent a single character, eight
9:41bits are required. That is eight
9:44capacitors. This set of eight bits is
9:46what we call a bite. One character
9:49equals one bite of memory. If you create
9:51a new text file and type only the letter
9:54A, the size of that file will be one
9:56bite. If you type hello five letters,
9:59the file size will be 5 bytes. This
10:02calculation works exactly if you do it
10:04in command prompt or in older DOS
10:07systems. In Windows, however, the file
10:09size will appear larger because Windows
10:12automatically adds extra formatting
10:14information. The important point is
10:16this. Whenever we type any text, every
10:19character has a corresponding ASKI code.
10:22That code has a corresponding binary
10:24code. And in memory, the on-off states
10:27of capacitors represent that binary
10:29code. This is how all text content is
10:32stored inside a computer. Now, let us
10:35see how an image or a picture is stored
10:37in computer memory. Things change a
10:40little here because images need to
10:42represent different colors. Inside a
10:44computer, an image is created by putting
10:47together tiny dots called pixels. If you
10:50zoom into an image closely, you can see
10:52the individual pixels that make it up.
10:54Suppose we have an image that is 100
10:57pixels wide and 100 pixels tall. That
11:00means the image has a total of 10,000
11:02pixels. Each of those pixels can have
11:05its own color. So when storing an image,
11:08it is not enough to save only how many
11:11pixels there are. The computer must also
11:14save the color of each pixel. For now,
11:17let us assume we are using a computer
11:19with an 8 bit color system. That means
11:21each pixel will be defined by 8 bits.
11:24Earlier, we saw that 8 bits can create
11:27256 different combinations. With these
11:31combinations, we can represent 256
11:34different colors. These are the colors
11:37shown here. The very first color
11:40corresponding to this binary code is
11:42black. The last one, the 256th color is
11:47white. All the other colors fall in
11:49between, each mapped to its own binary
11:52code. So in the 8- bit color system,
11:55each pixel is represented by 8 bits. For
11:58example, if the first pixel of our image
12:01is white, its binary code will look like
12:04this. 1 1 1 1 1.
12:07In this way, every pixel in the image
12:10has its own 8- bit binary code. Since 8
12:13bits make one bite, each pixel requires
12:16one bite of memory. That means for our
12:19example image with 10,000 pixels, the
12:21file size will be 10,000 bytes. So, the
12:25image you see on your screen with all
12:27its colors is ultimately stored in a
12:30computer as nothing more than zeros and
12:32ones. In other words, it is stored as a
12:35set of capacitors each in one of two
12:38states on or off. We have now seen how
12:41text is stored and how images are stored
12:44and the difference between them. In the
12:46same way, there are specific methods for
12:48storing music and for storing video. But
12:51in the end, no matter what type of data
12:54it is, everything in a computer is
12:56stored in the same simple way as on and
12:59off states. What we have explained so
13:02far is the most basic and simple way to
13:05understand how computer memory works. In
13:08reality, modern computers function in
13:11ways that are a little more complicated.
13:13Let me quickly mention some of those
13:15differences. Earlier, when we spoke
13:17about storing image colors, we
13:19considered an 8-bit color system. That
13:22system can only produce 256
13:25colors, but this gives only one or two
13:28shades for each main color. For example,
13:31the ASI table of 8-bit colors might show
13:34only three or four shades of yellow and
13:36red. But if we want to display a picture
13:39of a sunset, we need a smooth transition
13:41from yellow to red with many shades in
13:44between. That is not possible with only
13:478 bits. That is why today's computers
13:50use a 24bit system often called the true
13:53color system. Here 8 bits are used for
13:56red, 8 bits for green and 8 bits for
13:59blue together making 24 bits. With this
14:03system 256 * 256 * 256 = 16.7 million
14:11colors are possible. Of course, as the
14:14number of colors increases, the file
14:16size of the image also increases.
14:18Similarly, earlier we said that an image
14:21of size 100x 100 pixels or 10,000 pixels
14:25in total would need 10,000 bytes to
14:28store in memory. Saving an image like
14:31this is called the RAW format. But
14:34saving images in RAW format takes up a
14:37lot of space. That is why we often use
14:39compressed formats to reduce file size.
14:42One common format is JPEG. Using such
14:46compression, we can make image files
14:48much smaller. Now, let us return to
14:50memory itself. We said earlier that
14:53computers use capacitors and transistors
14:55to store data. This type of memory is
14:57called dynamic Ram. The smallest unit
15:01here is one capacitor and one transistor
15:04which together can store one bit. So
15:07when we say a computer has 4 GB of RAM,
15:11it means there are about 35 billion of
15:13these tiny memory units inside it. That
15:16sounds unbelievable. But remember these
15:19capacitors and transistors are not the
15:21large components we see in electronics
15:23shops. They are manufactured at the
15:25scale of nanometers. That is how
15:28billions of them can fit into a single 4
15:30GB memory chip. Modern computers use
15:34many other ways to store memory besides
15:36capacitors and transistors. For example,
15:39hard disks use magnetic discs and memory
15:42sticks use specially arranged
15:44transistors. There are many such
15:46technologies and I am not listing all of
15:49them here. But wherever it is stored,
15:52the principle remains the same. Data is
15:55ultimately stored as two states on and
15:58off. We represent these states as zero
16:01and one. the binary form. Computers are
16:04a rapidly developing field and by the
16:07time you watch this video, there may
16:09already be more advanced methods than
16:11the ones I have described. But I hope
16:13this video has given you a clear and
16:15simple understanding of how computer
16:17memory works. If you enjoyed this video,
16:20do not forget to like and share it. For
16:22more such videos, subscribe to this
16:24channel and enable the bell icon. And if
16:27you ever feel like asking yourself why
16:30should I know all this remember the
16:33reward of knowing is knowledge itself.

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