TCAT and S-TCAT instrument source code to place markers at each logical branch and call-pair. A directed graph that shows a module's control-flow structure, a call-tree that depicts an application's caller-callee relationship, and an object file are created from this instrumentation process. When TCAT and S-TCAT are used during testing, they report coverage status after tests have been executed against the instrumented source code.

T-SCOPE, on the other hand, visually demonstrates logical branches and call-pairs as they are being exercised while tests are running.

T-SCOPE links the created instrumented object file to its supplied runtime module, creating an executable. Once an executable is created, the user can choose to select modules' directed graph displays and an application's call-tree graph. Slider bars can also be selected that will show the percentage of coverage achieved for individual modules or the entire program, as each test is run.

When the necessary displays have been selected, thresholds can be set to show during test execution if a logical branch or a call-pair has been executed above or below the set threshold values.

When an application is executed, T-SCOPE updates the directed-graphs and call-tree by highlighting the exercised logical branches and call-pairs. Color annotation shows which logical branches and call-pairs have been hit less than the minimum threshold value, exercised more than the maximum threshold value, or executed between the two thresholds. This annotation clearly identifies areas that have been heavily tested or untested. Slider bars are also updated to show the percentage of coverage achieved for a module or a program after each test case is run.

T-SCOPE is especially useful for finding out why certain program parts are not covered and why certain parts are heavily exercised by the established test cases. By running test cases while using T-SCOPE, the user is better able to detect a bug or to create a new test case to exercise the un-hit code.