Microsoft Access 2000 uses the Unicode character-encoding scheme to represent the data in a Text, Memo, or Hyperlink field. In Unicode, each character is represented by two bytes instead a single byte.
An encoding scheme that stores each character in one byte limits you to a single code page — a numbered set containing a maximum of 256 characters. However, Unicode can support a maximum of 65,536 characters, because it represents each character as two bytes. As a result, the data in a Text, Memo, or Hyperlink field requires more storage space than it did in previous versions of Access.
You can offset this effect of Unicode character representation and ensure optimal performance by setting the Unicode Compression property of the field to Yes. This is the default when you create a new Text, Memo, or Hyperlink field. When the Unicode Compression property of a field is set to Yes, any character whose first byte is 0 is compressed when it is stored and uncompressed when it is retrieved. Because the first byte of a Latin character — a character of a Western European language such as English, Spanish, or German — is 0, Unicode character representation does not affect how much storage space is required for compressed data that consists entirely of Latin characters.
You can store in a single field any combination of characters that Unicode supports. However, if the first byte of a particular character is not 0, that character is not compressed.
Note Data in a Memo field is not compressed unless it requires 4,096 bytes or less of storage space after compression. As a result, the contents of a Memo field might be compressed in one record, but might not be compressed in another record.