FAQ: What are the item definitions available for ArcInfo GRID format?
What are the item definitions available for ArcInfo GRID format?
The ArcInfo GRID format uses the INFO data file format for its records.
The specification of the format for each record in an INFO file is referred to as the Item Definition. Each record can be up to 4,096 characters, or bytes, long. Any number of items can be defined for the data file. Items are defined by their name, data type, number of characters (or bytes) used to store values, a display width, and (for decimal numbers) the number of decimals that are to be displayed.
The fields of the INFO format have the following properties:
- any name with up to 16 alphanumeric characters.
- number of spaces (or bytes) used to store item values.
- number of spaces used to display the item values.
- the data type of the item.
No. of Decimals
- the number of digits to the right of the decimal place for item types which hold decimal numbers.
Supported item types
The following item types are supported in ARC/INFO:
- whole numbers stored as binary integers, with a width of either 2 or 4.
- For a width of 2, the maximum value is 32,767 and the minimum is -32,768.
- For a width of 4, the maximum value is 2,147,483,647 (2^31 - 1) and the minimum is -2,147,483,648 (-2^31).
- character (text).
- width is limited to 320 alphanumeric characters.
- dates in the form DD/MM/YY or DD/MM/YYYY.
- item width is fixed at 8 and stored internally as YYYYMMDD.
- decimal numbers stored in internal floating-point representation, with a width of 4 or 8 bytes only.
- A 4-byte width is single-precision real (approximately 7 digits of precision), and 8 bytes is double precision (approximately 15 digits of precision)
- integer stored as 1 byte per digit, width from 1 to 16.
- the range of integer values is has a maximum of 2,147,483,647 (2^31 - 1) and a minimum is -2,147,483,648 (-2^31).
While the width of 16 may imply a range with a maximum value of 9,999,999,999,999,998 (1exp16 - 2) and a minimum of -9,999,999,999,999,999 (-1exp16 + 1), the actual range is constrained by what can be represented with 32bit software.
- decimal numbers stored as 1 byte per digit (width from 1 to 16).
The information on item definitions is available in the online help at the following location:
Working with tables / Managing tabular data / managing attribute tables / Item definitions