The data contained in the files shown in Figure 9.9 provide evidence that may either
corroborate or refute audit objectives. Most of the tests described in the following section
involve using ACL to access and extract data from these files. For a detailed explanation
of ACL commands, review the instruction manual that accompanies the ACL software
and consult ACL’s online Help feature.
As a preliminary step in using ACL, each file needs to be defined in terms of its
physical location and its structure. Through a series of easy-to-use pop-up menus,
ACL’s Data Definition Wizard allows the auditor to specify the name of the file, specify
its location (on the mainframe or PC) and define the file’s structure in terms of the length of each field and the data type contained in each field (i.e., numeric, character,
or date). When the file definition is completed, it is saved under a unique name
assigned by the auditor. All future file access is accomplished by simply selecting the
file definition from an ACL menu. ACL automatically locates the file and presents it on
screen, where the auditor can review and manipulate its contents.
Sometimes the actual contents of a data field are different from what they are
supposed to be. For example, a numeric field in one or more records may contain alphabetic
data because of a program error or a clerical mistake. Also, a field may contain
corrupted data because of an error in the file-flattening process. Whatever the cause,
prior to performing any substantive tests on a new file, it is important to validate its contents.
Invalid data will distort the test results and may cause a system failure. ACL’s
Verify command analyzes the data fields in the selected file to ensure that their contents
are consistent with the field type in the file definition. Any validity errors detected by
ACL need to be traced to their source and resolved. The auditor may also find batch
control totals to be an effective means of verifying data integrity. For purposes of discussion,
we will assume that the files used in all tests described hereafter have been properly
defined and verified