How are your data structured? What do you mean by "rectangular" and "card image"?
The structure of a data file defines how records, or rows of data, are related to fields, or columns of data. The most common data structures found in the DSDR holdings are:
Rectangular or Logical Record File
In a rectangular file, each physical record or line of data is the same length. This is also referred to as an LRECL (logical record length) file because the length of the logical record (all data for a given record) is equal to the length of the physical record (one line of data). In other words, the data for each case or unit of analysis are stored in a single physical record.
Card Image or Multiple Record File
In a card image file, all of the data for a particular case are contained on more than one physical record or line of data. This format is a remnant of the time when data were input on punch cards that were physically limited to 80 characters per card. Therefore, if a line of data was longer than 80 characters, it had to be entered on multiple cards. Each card, or "deck," was numbered and stored in numerical sequence. With this format multiple records have to be read to build a complete case.
Hierarchical File
A hierarchical file contains multiple units of analysis, such as a household and an individual, that are related to one another through a structural hierarchy. Each unit of analysis has its own record structure or record type. The records for each unit of analysis are not necessarily the same length. When reading multiple levels into a statistical package at one time, cases at the lowest level of the hierarchy will define the unit of analysis.
Relational File
A relational file contains multiple units of analysis that are related to one another based on a predefined structure or variable, but not necessarily a hierarchy. For example, a data collection could have different record types for households, families, persons, wages, and general income, but these record types are not related to each other by a hierarchy of membership.