How to Download and Use Census Produced ASCII Data Files

Note: Users processing these ASCII files in a Windows environment should read carefully the File Information section of this document.

These files are intended for experienced users of census data, compressed files, and spreadsheet/database software. It provides quick access to data users, such as State Data Centers and news media, who need to begin their analysis immediately upon data release. Due to the size of the files, the user should have a fast download capability.

Once uncompressed, the data are in a flat ASCII format. The geographic file is in a fixed-field format; the two data files are in comma delimited format. No software is provided. Users of the ASCII data need to unzip the compressed file after downloading, then import it into the spreadsheet/database software of their choice for data analysis and table presentation.

There are three data files reflecting the three data segments. See below for more information on the data segments.

Once uncompressed, these files are in flat ASCII format. The geographic header file (see below) contains fixed fields while the data files (File01 and File02, see below), including the geographic link fields, are in comma-delimited format. These files have been constructed in a UNIX environment. They use an ASCII linefeed, chr(10), to indicate a new record.

For successful use with many programs running in a Windows environment, these files need to be modified to use the ASCII carriage return/linefeed sequence, chr(13) + chr(10) as a record terminator. This is an easy step in the UnZIP process using any UnZIP software which offers the conversion option. We tested PKZIP for Windows, version 4.00 following the steps outlined below. This PKZIP shareware can be downloaded from www.pkware.com. After installing PKZIP, do the following:

• Select the file
• Select the Extract option on the tool bar
• Select the options button at the bottom of the Extract page
• Under the Miscellaneous section, select the "DOS - convert to CR/LF"

The resulting file will meet the ANSI MS-DOS/Windows standard used by Access 97 and other MS Windows-based programs. If the data are being processed in a UNIX environment, they can be unzipped using any standard ZIP/UnZIP package.

These ASCII data are available as compressed files at the 90% (approximately) file compression ratio. Our estimate for a download for Texas is approximately 8 hours at the 56K bps speed. If you are using a modem/telephone line link to the Internet, we do not recommend using this option.

The data in the redistricting files and other Census 2000 summary files are segmented. This is done so that individual files will not have more than 255 fields, facilitating exporting into spreadsheet or database software. In short, to get the complete data set for the redistricting files, users must download all three files.

• Geographic Header file
• File01 (Tables 1 and 2) - Total Population
• File02 (Tables 3 and 4) - Voting Age Population

It is easiest to think of the file set as a logical file. However, this logical file consists of three physical files: the geographic header file, file01, and file02. This structure is a change from previous decennial census files.

The explanation below for linking the three redistricting test files requires specific location information for the geographic header. These are located in Chapter 7 of the Technical Documentation. A unique logical record number (LOGRECNO in the geographic header) is assigned to all files for a specific geographic entity; all records for that entity can be linked together across files. Additional identifying fields are also carried over from the geographic header file to the table files. These are file identification (FILEID), state/U.S. abbreviation (STUSAB), characteristic iteration (CHARITER), characteristic iteration file sequence number (CIFSN).

The geographic header record layout is identical across all electronic data products from Census 2000. Since the redistricting data files are quite simple, some of the fields, including some geographic header fields that appear in all three files (geographic header, tables 1/2, and tables 3/4) are not used. For example, the character iteration (CHARITER) field is only used in SF2/SF4. In the redistricting data file, it is always coded as 000.

For a layout of the individual tables for each file, see the Technical Documentation. Select Chapter 6, Summary Table Outlines.

               Geo file              File 1               File 2	
          _________________    _________________    _________________
State     unzipped   zipped    unzipped   zipped    unzipped   zipped	


Texas       296M       21M       233M       10M      232.5M     9.3M