Data Representation: Text

Data Representation: Text

Why do computers need a code for text?

Computers store everything as binary — 1s and 0s. Numbers can be represented directly in binary, but characters (letters, punctuation, symbols) have no natural binary equivalent. For a computer to store the letter 'A', it must be agreed in advance what binary pattern represents it. Without a shared standard, a file saved on one computer might produce garbled characters when opened on another. This is why character encoding standards were developed — they create a universal agreement between all computers about which binary number maps to which character.

ASCII — the original standard

ASCII (American Standard Code for Information Interchange) was developed in the 1960s and became the dominant early standard. Original ASCII used 7 bits, providing 128 possible values (0–127). Extended ASCII added an eighth bit, doubling capacity to 256 characters (0–255). Each character is assigned a unique code number, and the computer stores that number in binary.

The 256 characters break into key ranges:

• Codes 0–31: Non-printable control characters. These don't display on screen — they send instructions to devices. Code 7 triggers a beep, code 10 is a newline, code 13 is a carriage return.
• Code 32: The space character — the first printable character.
• Codes 48–57: The digits 0–9.
• Codes 65–90: Uppercase letters A–Z.
• Codes 97–122: Lowercase letters a–z.
• Codes 33–47, 58–64, 91–96, 123–127: Punctuation marks and symbols.

A key pattern to notice: 'A' is 65 and 'a' is 97 — a difference of exactly 32. This consistent offset means software can convert between upper and lowercase by simple arithmetic, without needing a lookup table.

How text is stored in memory

When you type the word "Hi!" on a keyboard, the computer stores three separate ASCII values: 72 (H), 105 (i), 33 (!). Each takes 8 bits (1 byte) of storage. A 100-character text file therefore requires 100 bytes of storage — before any formatting. Every space, every punctuation mark, every character you can type has its own unique ASCII code. The computer never stores the letter itself — only the number that represents it.

Unicode — solving ASCII's limitations

Extended ASCII was created before computing was truly global. Its 256 character slots are sufficient for English and some Western European languages, but completely inadequate for Chinese (70,000+ characters), Arabic, Japanese, emoji, and many other scripts. Additionally, different companies assigned different characters to the 128–255 slots, creating compatibility problems between systems.

Unicode solves this by using 16 bits per character, providing 65,536 possible values — enough for every major language on Earth, plus thousands of symbols and emoji. Unicode is now the global standard; when you send a text message containing an emoji, Unicode is the encoding making that possible. Crucially, Unicode is backwards-compatible with ASCII — the first 128 Unicode values are identical to ASCII, so existing English text files need no conversion.

File size implications

Because every character is stored as 8 bits (1 byte) in ASCII, calculating the storage requirement of a text file is straightforward: number of characters × 8 bits. A 1,000-character essay would need 1,000 bytes = 8,000 bits of storage. In Unicode (16 bits per character), the same essay would need 2,000 bytes — double the storage, but with the ability to represent any character from any language on the planet. This trade-off between storage size and language coverage is a key concept in data representation.