In a daily computer run to update checking account balances and print basic details on any customer’s account that was overdrawn, the overdrawn account of the computer programmer was never printed. Which of the following control procedures would have been most effective in detecting this irregularity? 

a. Use of the test data approach by the auditor in testing the client’s program and verification of the subsidiary file.

b. Periodic recompiling of programs from documented source programs, and comparison with programs currently in use.

c. A program check for valid customer code.

d. Use of a running control total for the master file of checking account balances and comparison with the printout.