reading from / writing to file : 2 dumb questions

[Richard Gaskin]

Jerry Jensen wrote:
 > On Sep 9, 2014, at 9:58 AM, jbv at souslelogo.com wrote:
 >
 >> Richmond,
 >> Thanks for your reply.
 >> Yes, I perfectly understand what happens, but my point is :
 >> why is it so ? What is the logic behind ?
 >> Is it specific to LC of is it closely related to the different OSes
 >> on which LC runs ?
 >> Why the fact of closing then reopening a file leads to overwriting
 >> its content ?
 >
 > Its held over from deep dark history. Open file meant the operator
 > should find the tape and mount it on the drive. Close file meant the
 > tape would be rewound so the operator could take it off the drive and
 > put it away.

It's more than a historical artifact, offering tremendous flexibility 
for traversing a file and reading/writing discrete parts of it.

Open for update allows this traversal gracefully, opening the door to a 
wide range of fairly sophisticated file I/O options, esp. useful for 
data too large to fit into RAM as a whole.

-- 
  Richard Gaskin
  Fourth World Systems
  Software Design and Development for the Desktop, Mobile, and the Web
  ____________________________________________________________________
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