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Computer Science IGCSEPDF 5
142 pagesrevision 46930
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Chapter 1: Number Systems, Data
Representation & File Management —
Detailed Notes
1.1 Binary Systems
The binary system is the foundation of all computer operations. It is a base-2 number system
meaning it only uses two digits: 0 and 1. Each binary digit is called a bit, the smallest unit of
data. A byte is a group of 8 bits, and a nibble is 4 bits.
Why Binary?
Computers use binary because circuits can easily represent two states: ON (1) and OFF (0). All
data and instructions in a computer are represented in binary.
Units of Data
Bit (b): single binary digit (0 or 1)
Binary to Denary Conversion
Nibble: 4 bits
Byte (B): 8 bits
Kilobyte (KB): 1024 bytes (2^10)
Megabyte (MB): 1024 KB (2^20)
Gigabyte (GB): 1024 MB (2^30)
Terabyte (TB): 1024 GB (2^40)
Conversions: Multiply or divide by 1024. Example: 2048 KB ÷ 1024 = 2 MB.