1.3 Data Storage & File Compression
Data Storage
Memory size is actually measured in terms of powers of 2, it's a system which is more accurate has been adopted by the IEC (International Electrotechnical Commission). Internal memories such as RAM & ROM use this.
Nibble
4 bits
Byte
8 bits
1 KB (kilobyte)
1000 bytes
1 MB (megabyte)
1000 KB
1 GB (gigabyte)
1000 MB
1 TB (terabyte)
1000 GB
1 PB (petabyte)
1000 TB
1 KiB (kibibyte)
1024 bytes (2¹º)
1 MiB (mebibyte)
1048576 bytes (2²º)
1 GiB (gibibyte)
1073741824 bytes (2³⁰)
Data Compression
Compressing data is useful as it saves storage space, reduces costs by using less bandwidth, and reduces the time taken to stream or transfer the file. There are two types of data compression:
Lossy
Lossless
Lossy
Upon compression, the unnecessary data is deleted
Original file cannot be reconstructed
Some loss of detail (lower quality in images & sound files)
Smaller file size
Sample answer:
Compression algorithm is used Original file cannot be restored Deletes unnecessary data from the file Removes sounds that cannot be heard by the human ear Reduces the sample rate & resolution
Lossless
Compresses a file by reducing the size of repeated areas (via RLE & Huffman)
RLE (run-length encoding) is used to replace sequences of repeated characters with a code
Huffman encoding replaces frequently used characters with shorter codes and the opposite
All the data from the original file can be reconstructed
No detail is lost
Larger file size
Sample answer:
Compression algorithm is used Original file can be restored RLE & Huffman encoding is used Repeated patterns are identified & indexed
Exam Questions
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