File Names and Attributes

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Every file you create on the flash disk has a file name and attributes. Both share a single text string that can be up to 56 characters long. The attributes (if any) are separated from the file name by a space. In other words, everything up to the first space is the file name, and everything else — attributes.

The file names are case-sensitive and can include any characters, except, obviously, the space. This includes "/" and "\". The flash disk does not support subdirectories, but it is possible to emulate them by including "/" or "\" characters in the file name. The "." character can be used too, so you can have any extensions you like. The attributes portion of the string may contain any characters whatsoever, including spaces.

It is quite common for file systems to define attributes for the files. Typically, however, these attributes are preset. That is, you have a fixed list of things you can define about the file, such as the creating time, read-only flag, etc.

The fd. object uses a different approach. In a system that only runs a single application at any given time, it makes no sense to have, say, a fixed read-only flag. There is only one application running, after all. This application probably knows what files not to touch anyway! Or how about the date and time of the file creation? Does it make sense to keep this on a system without a real-time clock? Quite obviously, no.

For the above reasons, the fd. object allows you to store any attribute data and interpret it in any way you want. There is an attribute string and you can fill it with any data of your choosing and in accordance with the needs of your application. And yes, you can implement the read-only flag and record the creation date and time — but only if you need to.

Here is an example where we create a file and set its attributes too:

 

...

fd.create("File1.dat R 25-JUL-2008") ' <File1.dat> is the file name, <R 25-JUL-2008> -- attributes, it is up to our program how to interpret this!

 

 

For more info on file attributes see Reading and Writing File Attributes.