Data File Structure / Content

This documentation provides a complete description of all data files included within the system.  These files are provided in the industry standard .DBF format, and are readable by other software programs.

CAUTION:   Although other programs can read .DBF files naturally, it is vital that you never modify the data directly.  Many programs that can "edit" .DBF files may, in fact, corrupt the data.  Consequently it is important to always work with a copy of a file rather than the one used by the system.

What is a data file ?

A data file contains all of the information entered into the computer by the operator(s).  Any program will usually contain many data files.  Sometimes these are all contained in one large file, called a database, and divided into smaller groups named tables.  In the case of The Auto Shop Writer, all data is maintained in independent files.  Each has a name that ends with .DBF.  These are often refered to dBase files because they were originally created in a format using the dBase program.  However, these files actually are 32bit data files, and use what are known as FoxPro compatible memo ( text ) fields and indexes.  Programs that cannot properly process DBF/.FPT/.CDX files will damage the data stored within these databases and may completely lose your information.

These files have the following elements:

Header

The first section of a file contains "Header" information, which describes the structure of the content of the file.  It includes the names, types, and size, of each field, plus the count of records in the file.  The program reads the header, and then uses the information provided to determine where records are located, and how to interpret the data.

Records

Data files are divided into individual records.  However, all of the information is written in "one continuous stream" on the hard disk, and divided into the individual records based on the information contained in the header.

A record contains the information specific to one "data entry", ie. one part in inventory, or one client in the customer file.  Each data file may contain a single record, or may contain thousands of records.

Fields

Each piece of information is stored in a "field", and there are numerous fields in a record.  Each field is defined with a type, and a length.  When looking at a field on a data entry screen, the type and size is not specified, but in the actual file definition it is very clear.  There are several data types used in The Auto Shop Writer:

•Character - Character fields contain letters and numbers, and are usually of a fixed length.  They contain names, addresses, descriptions, and other useful information.

•Numeric -  A numeric field contains only numbers, and may be used for calculations

•Logical - A logical field may be either True or False, Yes or No.  It is like a toggle, and contains no data.

•Date - A date field holds a date which can be used to match against other dates, or to perform calculations, ie. elapsed time.

•Memo - A memo field contains Character data, but is of variable length.  It is used to contain longer sections of text.  Because it is variable length, one record may take up a little, or no, space, while another record may have a very long entry.

Each field also has a specified length, except for the memo field.  Date fields are always a size of 8, while logical fields are always 1.  All other fields may vary in size.  The Memo fields have a reference length of 10, and numeric fields specify the overall length, and the number of digits to the right of the decimal place.

Possible supplemental uses of ASW data files

Merge Data

Information from data files can be copied to other files which can then be read by a word processor and used to merge the information into documents.  This is typically used for sending out mail information, but may be used to build custom reports, or to build custom worksheets.

Spreadsheets

Spreadsheets are used to look at the data in table form ( rows and columns ).  Also, if the data in the spreadsheet is built with special files created as a "subset" of The Auto Shop Writer databases, then the user may elect to manipulate some of the numbers to "project" various scenarios, ie. what would happen if part prices were increased by 3%.  Spreadsheets are very useful analysis tools, and the ability to extract data from the management system and plug it in directly eliminates the need for repetitive data entry.

Graphics

Many times custom graphs can be created from a commercially available spreadsheet program.  Once the data is extracted from the data files, and presented in tabular form, a graph can be designed.

Custom Reports

There are programs available that permit the creation of custom reports.  One of the best known is Crystal Reports which can be obtained at most software stores.  Full instructions for creating special reports would be included within the product itself.