9 - File I/O – Files and Records and Fields, Oh My!

Summary

VB Quip

On two occasions I have been asked (by members of Parliament), “Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?” I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.

–Charles Babbage

By now you've come to realize that the real bottlenecks of your programs are input and output. Some of that is because users can only type and click so much and some of it is because input is repetitive. You've created useful output but have been unable to hang on to it. So far, every program run has meant starting from scratch with your data, entering it as needed, calculating the results, and then losing all of that work with a click of the Exit Button. No more. File input and output gives you the ability to store data and retrieve it as needed. File input takes data stored in a file and puts it into your program. File output stores the results in a file so you can use the data at a later date. This chapter covers the details of opening a data file, reading the data, processing the data, displaying the output, and writing the results to a file.

The Basics of File Input and Output

A data file, for our purposes, is a text file. Each line in the file is a record. A record consists for one or more fields.