Miscellaneous - Data Units, Binary, and Character Encoding

🧠 Data Units, Binary, and Character Encoding

A structured guide to CPU data units, binary representation, and character encoding,
focused on how computers actually store and process data.

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1️⃣ Word — CPU Processing Unit

What is a Word?

A word is the natural data size a CPU can process in one operation.

It is tied to:

• Register width
• ALU operation size
• CPU architecture (16-bit, 32-bit, 64-bit)

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Common Data Units

Unit	Meaning	Typical Size
Half Word	Half of a word	16 bits
Word	CPU-native size	32 or 64 bits
Double Word (DWORD)	Twice a word	64 bits
Quad Word (QWORD)	Twice a double word	128 bits (SIMD)

📌 On modern systems, word = 64 bits.

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Why Word Size Matters

• Determines integer & pointer size
• Affects memory alignment
• Impacts CPU performance

Misaligned memory access can slow execution.

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2️⃣ Binary vs Decimal — Number Representation

Binary (Base-2)

• Uses 0 and 1
• Native format for hardware logic

Example:

Binary: 10000₂
Decimal: 16₁₀

Decimal (Base-10)

• Human-friendly system
• Converted to binary internally

📌 CPUs always operate on binary.

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3️⃣ Signed vs Unsigned Integers

Type	Range (8-bit Example)
Unsigned	0 to 255
Signed (Two’s Complement)	-128 to 127

Two’s complement allows efficient negative number arithmetic.

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4️⃣ Character Sets — Mapping Characters to Numbers

A character set maps text characters to numeric code points.

Example:

'A' → 65

It defines:

• Supported characters
• Numeric values assigned to them

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5️⃣ Encoding vs Decoding

Encoding

Characters → Bytes

Decoding

Bytes → Characters

Text → Encode → Bytes → Decode → Text

Encoding mismatch causes mojibake (broken text).

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6️⃣ ASCII — The First Standard

• 7-bit code points (0–127)
• Supports English letters, digits, symbols

Structure

• 7 bits = character
• 1 bit = optional parity bit

Example:

'A' = 65 = 1000001₂

Limitations: ❌ No multilingual support

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7️⃣ Unicode — Universal Character Set

Unicode assigns a unique code point to every character worldwide.

Examples:

'A' → U+0041
'한' → U+D55C
'😀' → U+1F600

Unicode defines characters, not storage format.

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8️⃣ Unicode Encodings — UTF-8, UTF-16, UTF-32

Unicode must be encoded into bytes.

UTF-8

• 1–4 bytes
• ASCII compatible
• Web & Linux standard

UTF-16

• 2–4 bytes
• Efficient for East Asian text
• Used in Windows, Java

UTF-32

• 4 bytes fixed
• Simple indexing
• Memory heavy

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Encoding Comparison

Encoding	Byte Size	Pros	Cons
UTF-8	1–4	Efficient, standard	Variable length
UTF-16	2–4	Good for CJK	Surrogate pairs
UTF-32	4	Simple	High memory use

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9️⃣ How CPUs See Text

CPUs do not understand characters — only binary numbers.

Processing flow:

Characters → Code Points → Encoded Bytes → Binary → CPU

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🔟 Endianness — Byte Order

Type	Order
Little Endian	Least significant byte first
Big Endian	Most significant byte first

Important for networking & file formats.

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🎯 Developer Takeaways

✔ Word size impacts memory & speed
✔ Binary is the CPU’s native format
✔ Unicode is required for global text
✔ UTF-8 is the modern default
✔ Encoding mismatch breaks text
✔ Endianness matters in low-level programming