The sector device is a device for 

The correct answer is Increasing the capacity of an array with the aid of an empty digit.

Key Points

• Sectorising Digits/Device:
  • ​This is an effective device to accommodate a subject at a proper place in an array even if no vacant place is there.
  • For this Ranganathan invented an ingenious method of empty digits, now also called Sectorising Digits.
  • To increase the capacity of an array, CC has introduced what is called an empty digit. An empty digit has no semantic value, but it retains the ordinal value.
  • Ranganathan sets aside 0,9,z, and Z as empty digits.
  • These digits are never used alone but are used as repeater digits to extend an array.

Additional Information

• Digits T, V, and X are set aside as emptying digits as these empty a preceding digit of its meaning but allow it to retain its ordinal value.
• To make further rather almost unlimited interpolation in the Colon Classification U, W
  and Y have been postulated as Empty-Empty digits. 
• The four major devices used in CC are:
  • Chronological device
  • Geographical device
  • Subject device
  • Alphabetical device