Visual Basic .NET 2005 Express - Programming Logic and System Architecture

This is a free tutorial to help beginning programmers get up to speed using Microsoft Visual Basic 2008 Express. To get the most from this tutorial, you might want to start at the beginning. The Complete Table of Contents for this course can be found on the first page of part 1: A "From the Ground Up" Tutorial.

To a very large degree, the miracle that is personal computing was made possible by a type of programming that's usually called, event-driven logic. Many, perhaps most of you, might not have seen anything else. But "back in the day" - the "mainframe" era of computing from the 1960's through the 1980's - programming was nearly all sequential logic. When PC's (and Visual Basic) took center stage, a whole new way of writing programs was invented.

Sequential Logic

In our review of the fundamentals, we're going to cover event-driven logic and how it's different from sequential logic. Then we'll use that understanding as a springboard to see not only how programs are written in the .NET era, but also how complete data processing system architecture fits together in the real world.

Both sequential logic and event-driven logic are used in all of the example programs we've done here, but there's a difference that you have to be completely clear about to write your own VB.NET programs. If you don't understand event-driven programming, you don't understand programming.

In the mainframe era, data was mainly processed in big "batches". Let's look at how a typical bank would process data for their accounts as an example of the way it used to work.

At the end of a day, all of the transactions for a bank (deposits, withdrawals, interest payments and so forth) would be in one file and all of the accounts for the bank would be in another file. Both files would be sorted into account number sequence and each transaction would be applied to each account. A new master account file would be created (and an inevitable error file, for all the data that didn't work for some reason) for the next day's business.

If you ever hear someone say, "Oh, we have to wait for the computer files to be updated." - It's still batch processing. But you might never run into this today because this type of processing is close to being extinct.

The central feature of sequential, batch processing is that a program is started, runs through a fixed series of steps, and then stops. In today's programs, a call to a single subroutine or function remains a sequential process. But in the mainframe era, the whole system worked that way.

The next page shows you how most computing, especially PC computing, is done today.