Data Dependency Types:

Structural Dependence: If the file-system programs are affected by change in the file structure, they exhibit structural-dependence.  For example, when we add date-of-birth field to the CUSTOMER file, the programs that access CUSTOMER will not work with the new CUSTOMER file structure. Therefore, all of the file system programs must be modified to match to the new file structure.

Data Dependence: If the file-system programs are affected by change of the data-type, they exhibit data-dependence.  For example, change in the characteristics of data (data-type), such as changing a field from integer to float, require changes in all the programs that access the file.   The practical significance of data dependence is the difference between the logical data format (how the user views the data) and the physical data format (how the computer stores the data).