Fast Track 2.3

Writing to a data file

WRITE #3, USING “N 8, C 50”: cusnum, email$ 

Writes the customer number and email to file #3, which we just opened. (File numbers can be replaced with labels to make your programs clearer). The N 8 means that the cusnum variable can be up to 8 digits long, while the C 50 means that the email$ variable can be up to 50 characters. These form descriptions can be put into a FORM statement and referenced by a line label, as you'll see in the READ example coming up.

Closing a data file

Closing a file is the easiest step:

CLOSE #3:

Reading a data file, and then using that information to print

Later, if we want to print out the list of names and email addresses (or use them to send out statements!) we open the file again.

OPEN #EMAIL_FILE: “Name=customerlist, recl=58”, INTERNAL, INPUT ERROR errorhandling

Reading and making changes to that information using GRID and LIST

READ #EMAIL_FILE, USING “N 8, C 50”: cusnum, email$ 

This will read the first record in the file and store it under the variable names cusnum and email$. But this is a whole list and so we will have to repeat the READ command and store the information into MAT cusnum and MAT email$. Using a For Next statement.

Emailform: form N 8, C 50
While N=1 
READ #EMAIL_FILE, USING emailform: cusnum, email$ EOF lastrecord
Loop
lastrecord: ! Read is done.

CLOSE #EMAIL_FILE: