You have probably encountered terms professionally or in day to day life like "4GB RAM", "1TB hard drive" or "64GB memory". Likely you encountered these while reading about computer or phone specifications. These concepts represent information regarding data storage and memory on a computer system.

Storing information on computers requires the use of memory. It is not possible to store every and any possible data on computers, there are certainly restrictions. Machines do not have an infinite amount of memory.

To effectively store data on computers, it is important to know how the storage mechanism of computing systems takes place. To utilize computing resources effectively, data sizes are an important understanding. They are units of measurement for computers, which measure how much space your data takes up in the computer.

Memory

To understand storage systems and data sizes in computers, it is important to learn more about memory first.

Computers have two kinds of memories; volatile and non-volatile. Volatile memory is a temporary memory that loses content after a computer restarts.

1. RAM (Random Access Memory) is an example of this type of memory. All your unsaved data gets stored on RAM, which is temporary, and thus, in case of any issues, you lose all this data.

2. Non-volatile memory is permanent. ROM is an example of non-volatile memory, which stores programs related to computer boot etc.

Data stored in these memories is limited. A RAM (as of this writing) commonly has a size of around 4GB to 8GB, and a ROM ranges from 4MB to 8MB. Let's learn about what these sizes mean in the next section.

How is Data represented in Computers?

Just as you represent the length in its unit of measurement (centimeters, meters, kilometers), computers also have a unit of measurement for their data storage. These are specific to computer systems, as they are defined in binary bits. For computers, you can measure the size of memory using bytes, kilobytes, megabytes, up to petabytes (and even greater)-- with new allocation levels being created.

Bits (b)

The basic unit of all computers is bits. Bits can store two values, 0 and 1. The combination of these bits is also known as machine code. All other units of memory are defined as a combination of these bits (in machine code!). This means that all the data that is stored on a computer is a mere combination of 0s and 1s!

Byte (B)

A byte is a unit of data storage on computers, made up of 8 bits. This means that it can store 256 possible binary values, as 2⁸ = 256 (since there are 2 bits, and 8 bits make up 1 byte). A single byte can represent one character, whether it be a number, letter, or symbol. The below illustration shows how these representations are eventually translated to bit representation. Larger units of memory are now made up of bytes.

KiloByte (KB)

You would probably think that since kilo refers to 1000, 1 Kilobyte = 1000 bytes. While that is somewhat true, a more accurate value of 1 kilobyte would be 1024 bytes.

This is because computers follow a binary system that is based on the powers of 2. Therefore, we search for the power of 2 which is closest to 1000. This is 2¹⁰ = 1024. Thus, 1 KiloByte = 1024 Bytes. If we express in terms of bits, 1 kilobyte = 8 bits x 1000 bytes = 8000 bits. Here we approximate the value of 1 kilobyte as 1000 rather than 1024.

Small files (such as low-quality images or text documents) are represented in kilobytes.

Megabyte (MB)

Megabyte is greater than a kilobyte and is equal to 1 million bytes. In terms of kilobytes, 1 megabyte = 1024 kilobytes. If we want to express a megabyte in bits, again we approximate the million to 10⁶. This means the number of bits for a megabyte would be 8 x 10⁶.

An HD image, a three-minute MP3 audio file, or short, low-resolution video files are stored in megabytes.

Gigabyte (GB)

Giga refers to a billion. Similar to a megabyte, defining a gigabyte in terms of the previous memory unit will be, 1 gigabyte = 1024 megabytes. Expressing this in bits would be 8 x 10⁹. A gigabyte is huge, it can even store a full 1 - 1.5 hour HD movie!

Terabyte (TB)

After a gigabyte, the next memory unit is a terabyte. A terabyte is larger than a gigabyte and thus, 1 terabyte = 1024 gigabytes. Terabytes take enormous amount of bits for data representation, around 8 x 10¹² bits.

Modern hard disk drives or laptops have storage space of around 1 to 2TB. This gives the users a lot of storage space which lasts for a long time.

Petabyte (PB)

Even greater than a terabyte is a petabyte, and this is the last memory unit that we will define in this lesson. 1 petabyte is 1024 terabytes, which is one quadrillion. You must be wondering, when are such large storage units used?-- as we usually see units up to terabytes more commonly.

But current technologies employ the use of terribly huge databases, which require even storage capacities in petabytes. One example would be mobile phone networks which transmit over 20 petabytes of data to and from users every day, or Google's servers which process around 24 petabytes of information every day.

Summary

To understand the memory structure and performance of the system, knowledge about data sizes is necessary. The memory units discussed in this lesson with their example usages are summarized in the table below.

One Pager Cheat Sheet

• We will learn about data sizes and their importance to effectively use computing resources in this lesson.
• It is important to become familiar with volatile and non-volatile memory, typically RAM and ROM respectively, as they have limited sizes ranging from 4MB to 8GB.
• Data is stored and measured in computers using binary bits with units ranging from bytes up to petabytes and beyond.
• All data, no matter its form, is stored as combinations of 0s and 1s (in machine code) on a computer.
• A byte is a unit of data storage made up of 8 bits, allowing it to store 256 binary values, representing a single character, number, letter, or symbol.
• The word "Monday" requires 6 bytes of memory due to each character being represented by 1 byte.
• While it is commonly thought that 1 Kilobyte = 1000 bytes, computers follow a binary system which means that 1 KiloByte = 1024 Bytes, which can be further represented as 8 bits x 1000 bytes = 8000 bits.
• The size of the text document in kilobytes is equal to 10,000 words multiplied by 5 letters per word and 1 byte per letter, divided by 1024, which equals 50 KB.
• A Megabyte (MB) is equal to 1 million bytes or 1024 kilobytes, and is expressed in bits as 8 x 10⁶, with HD images, audio and short video files typically stored in megabytes.
• A gigabyte (GB) is equivalent to 1024 megabytes (MB), or 8 x 10⁹ bits and is capable of storing a full 1 - 1.5 hour long HD movie.
• A terabyte (TB) is larger than a gigabyte and provides a storage capacity of up to 8 x 10¹² bits, allowing modern hard disk drives or laptops to have storage spaces of up to 1 to 2TB.
• Today, large databases require capacities of petabytes, like mobile phone networks which transmit up to 20 petabytes of data and Google's servers which process 24 petabytes of information every day.
• 1 GB is equivalent to 1,000,000 KB or 1,024 MB, so multiplying 1.5 GB by 1,000,000 (in decimal) or 1,024 (in binary) gives us 1,500,000 KB (in decimal) or 1,572,864 KB (in binary).
• Knowledge of data sizes is necessary to understand the memory structure and performance of a system, with various units ranging from bits to petabytes used to store different elements such as machine code, characters, documents, audio and video files, movies, and hard disk drives.