If you are working in real world application then you may frequently face scenarios where you have to Compare data e.g. you get two lists of values and you want to know which values are common between two lists, which values only exists in the first list and which values only exists in the second list. If the list contains just 5 to 10 values you can do it easily with your eyes but what is fun if a programmer doing the task manually. You should be able to leverage all the tools available to you to do this comparison reliably. One of such ubiquitous and omnipresent tool is Microsoft Excel which is much more powerful then you can think of. It's like your brain, most of us just use 5% of Excel and a good knowledge of Excel's little bit advanced functionality e.g. VLOOKUP can be very helpful while comparing the list of values and reconciling data between different worksheet.