84. OCR A Level (H046-H446) SLR13 - 1.4 Character sets

Summary

This video explains how character sets like ASCII and Unicode are used to represent text in computer systems. It starts by describing how binary code (0s and 1s) is used to store data and how different characters must be assigned unique binary codes. The video covers the evolution from 7-bit ASCII, which could represent 128 characters, to Unicode, which now supports thousands of symbols, including emojis, across languages. It also touches on storage efficiency, comparing the byte size differences between ASCII and Unicode encoding.

Takeaways

• 💻 Computers store all data, including text, as binary (zeros and ones).
• 🔤 Each character, such as letters and emojis, must have its own unique binary code to be stored.
• 🔢 Using one binary digit (bit) can represent only two characters (e.g., A and B), while more bits can represent more characters.
• 🔡 To store the alphabet (26 letters), at least 5 bits are needed, as 2^5 = 32 possible characters.
• 🔠 Character sets are standardized systems where each character is assigned a specific binary number, recognized by all computers.
• 📜 ASCII (American Standard Code for Information Interchange) is a 7-bit character set, representing 128 characters.
• 🇨🇳 Extended ASCII uses 8 bits, allowing up to 256 characters and supporting foreign languages and symbols.
• 🌍 Unicode is a universal character set that allows the representation of characters from all languages and modern symbols like emojis.
• 🔄 Unicode can be stored using 8, 16, or 32 bits, which means it takes up more space than ASCII for certain characters.
• 📝 Although ASCII is a subset of Unicode, ASCII is still used in some cases to save storage space as it uses fewer bits.

Q & A

How does a computer store characters such as letters and symbols?

A computer stores characters by converting them into binary codes, which are strings of 0s and 1s. Each character is represented by a unique binary sequence that the computer recognizes.

Why can't we represent all characters with just one binary digit?

One binary digit can only represent two possible values, 0 or 1. Since there are more characters than just two, we need more bits to represent additional characters.

How many bits are needed to represent the 26 letters of the alphabet in binary?

At least 5 bits are needed to represent the 26 letters of the alphabet. This allows for up to 32 unique binary combinations.

What is a character set and why is it important?

A character set is a defined list of characters, where each character is represented by a unique number or binary code. It's important because computers need to use the same binary code to represent the same character consistently across different systems.

What is ASCII and how many characters does it represent?

ASCII, the American Standard Code for Information Interchange, is a 7-bit character set that represents 128 unique characters. It was later extended to 8 bits, allowing for 256 characters.

Why was ASCII extended to an 8-bit code?

ASCII was extended to 8 bits to include additional characters, such as those from foreign languages and graphical symbols, expanding the set to 256 characters.

What is Unicode and why was it created?

Unicode is a universal character set designed to include all the characters from every written language, historical scripts, and modern symbols, such as emojis. It was created to support a fully international and multilingual character set.

How does Unicode differ from ASCII?

Unicode supports many more characters than ASCII and uses 8, 16, or 32 bits per character, while ASCII is limited to 8 bits. Unicode is designed to accommodate all possible characters across languages and scripts, whereas ASCII is limited to a subset of characters.

Why don't we use Unicode for all text storage instead of ASCII?

While Unicode can store all possible characters, it takes up more space compared to ASCII. ASCII is still used in cases where space efficiency is important and where its limited set of characters is sufficient.

How are characters like emojis stored in computer systems?

Emojis are stored using Unicode, which allows for a wide range of characters beyond letters and symbols. Unicode assigns a unique binary code to each emoji, ensuring it is recognized across systems.