For example, if the Customer record were modified to expand the ZIP Code field from five to nine dig...

1. Technology :: File Processing Systems
For example, if the Customer record were modified to expand the ZIP Code field from five to nine
digits, all programs that use the Customer record need to be modified, even if they do not use the
ZIP Code field.
Even the earliest business computer systems were used to process business records and produce
information. It is difficult to represent complex objects using file processing systems. There might be
twenty programs that process the CUSTOMER file. The major problem concerns data integrity. This
last weakness of file processing systems may seem a bit theoretical, but it is an important
shortcoming.
. A collection of data has integrity if the data is logically consistent. Although file processing systems
are a great improvement over manual systems, they do have the following limitations:
Data is separated and isolated.
Data is often duplicated.
Application programs are dependent on file formats.
It is difficult to represent complex objects using file processing systems. If a member were to change
his or her name or address, then all files containing that data need to be updated. The problem with
this arrangement is that changes in file formats result in program updates. A change like this one
means that a programmer needs to identify all the affected programs, then modify and retest them.
The danger lies in the risk that all files might not be updated, causing discrepancies between the
files. Although this duplicate data wastes a small amount of file space, that is not the most serious
problem with duplicate data. These systems stored groups of records in separate files, and so they
were called file processing systems. It is also very frustrating to have to modify programs that do not
even use the field whose format changed. In file processing systems, the physical formats of files and
records are entered in the application programs that process the files. In the record club example, a
member's name, address, and membership number are stored in both files. This data is then used to
produce the information. This means, in part, that duplicated data items agree with one another.

2. This is both time consuming and error-prone. They were generally faster and more accurate than
equivalent manual systems. Somehow you need to extract data from both the CUSTOMER and
ORDER files and combine it into a single file for processing. To do this, computer programmers
determine which parts of each of the files are needed. Then they determine how the files are related
to one another, and finally they coordinate the processing of the files so the correct data is
extracted. Data is separate and isolated. Application programs are dependent on file formats. Recall
that as the marketing manager you needed to relate sales data to customer data. Imagine the
problems of extracting data from ten or fifteen files instead of just two! Data is often duplicated.
Data integrity problems are serious. At least one of them will be incorrect, but who can tell which
one? When this occurs, the credibility of the stored data comes into question. In COBOL, for
example, file formats are written in the DATA DIVISION. Poor data integrity often develops in file
processing systems. A report from one application might disagree with a report from another
application. If data items differ, inconsistent results will be produced