Binary Text: ASCII and Unicode

Computers are essentially giant calculators that only speak in binary (0s and 1s). To display text, we need a 'codebook' that tells the computer which number represents which letter. This is where ASCII (American Standard Code for Information Interchange) comes in. Created in the 1960s, it originally used $7$ bits to represent $128$ different characters ($2^7 = 128$). This included uppercase letters, lowercase letters, numbers, and basic punctuation. For example, the capital letter 'A' is assigned the decimal value $65$, which in $8$-bit binary is $01000001$.

While ASCII worked for English, it couldn't handle the thousands of characters in languages like Chinese, Arabic, or even modern emojis. To solve this, Unicode was developed. Instead of being limited to $128$ characters, Unicode can represent over $140,000$ characters using up to $32$ bits. The most common version, UTF-8, is backwards compatible with ASCII. This means the first $128$ characters of Unicode are identical to the ASCII table, ensuring that old files still work on new systems while allowing for a global reach.

To read a binary message, you must first group the bits into bytes (8-bit chunks). Each byte corresponds to a decimal number on the ASCII/Unicode table. This process is called decoding. If the computer misinterprets the encoding (e.g., trying to read Unicode as ASCII), you get 'mojibake'—those strange, unreadable symbols you sometimes see on broken websites.