variable length field
A record structure that holds fields of varying lengths. For example, PAT SMITH would take nine bytes and GEORGINA WILSON BARTHOLOMEW would take 27 plus a couple of bytes that would define the length of the field. If fixed length fields were used, at least 27 bytes would have to be reserved for both names.
More Programming Effort
There's more programming with variable length fields, because every record has to be separated into fixed length fields after it is brought into memory. Conversely, each record has to be coded into the variable length format before it is written to disk.
The Compression Alternative
The same storage savings can be achieved by compressing data stored on disk and decompressing it when retrieved. All blank spaces in fixed length fields would be filtered out. For acceptable performance, this method must be well integrated into the operating system. See real-time compression.
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| Size Matters |
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| Variable length fields eliminate the need to guess the maximum size of a fixed length field ahead of time. In the 1980s, Zzherobrouskievskieskieea, with its, count 'em 25 letters, was an actual name in the New York City phone book. Although this was a public document, the numbers have been obscured for privacy. |