Information Technology Reference
In-Depth Information
4. A report program
You can do a great deal with a computer program but in general all programs do
the same thing. They read data and produce output, either another file or a listing on paper
or on a screen. In the process, sometimes files are updated. The data may be obtained
from the system somehow, from screen input or from another file. Despite this simple
breakdown, the process could get quite complicated. A program could involve reading a
dozen files to get dif ferent kinds of data and then produce a few files. A data entry
program might involve a screen to allow input, which could be quite complicated. It
really depends on the system and what kind of computer you have. Fortunately our system
will not be complex and so you may be a little upset to see more complexity when you get
to a different system.
Here are a few examples to illustrate this fact. It is discovered that someone
messed up the account file for all the begin dates. Instead of 2000 or 2001 for the y ear,
each record has 0000 or 0001 for this value. Someone writes a program to correct this
situation. The input to this program is the account file and the result will be either a new
one or an updated account file. This all depends on what type of file it is. In either case
the two files will be different, with the new one having the correct begin dates. Thus the
program will read a file and create an output file. There could be another output file,
namely a report to list the records that were changed.
The account file needs to be updated with new accounts from time to time so there
is a program to allow input into the file. Once again we have an input file in the data
being keyed and probably two output files, the updated account file as well as some kind
of report. Even though the report file is not completely necessary, it is probably a very
good idea to show the addition of the new accounts.
Our first program will read the account number file and produce a listing of the
fields on it. Specifically, we will read a file and produce output in the form of a report,
but just one record will be listed. That's very restrictive, but we'll get into reading the
entire file later.
