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Top Forums UNIX for Dummies Questions & Answers trying to understand rationale of unix stream i/o concept Post 302333217 by kaychau on Saturday 11th of July 2009 05:19:32 PM
Old 07-11-2009
trying to understand rationale of unix stream i/o concept

I am an entry level programmer with no formal training in computer science. I am trying to enhance my conceptual knowledge about operating systems in general.

I have been using the C programming language on Linux systems for some time and have used the traditional unix stream I/O APIs. The introductory material in books and on the web, typically introduce the unix stream I/O model as "basic unix I/O model is a stream of bytes which can be accessed sequentially or randomly". I understand this part, but I am unable to visualize how else would one access the data. Were the I/O models different before the I/O stream model came in to existence? Are there models in current computing paradigm which are different from the stream I/O. I will appreciate if some can help me visualize both the stream I/O model vs other models (if they exist or existed). Pros-Cons will be a great addition too.

In addition, I came across the following statement on the web (I/O System)

"The basic model of the UNIX I/O system is a sequence of bytes that can be accessed either randomly or sequentially. There are no access methods and no control blocks in a typical UNIX user process."

I do not understand the last statement - what are access methods and control blocks in the context of I/O?

Thanks
Kay
 

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FANN_CREATE_TRAIN_FROM_CALLBACK(3)					 1					FANN_CREATE_TRAIN_FROM_CALLBACK(3)

fann_create_train_from_callback - Creates the training data struct from a user supplied function

SYNOPSIS
resource fann_create_train_from_callback (int $num_data, int $num_input, int $num_output, collable $user_function) DESCRIPTION
Creates the training data struct from a user supplied function. As the training data are numerable (data 1, data 2...), the user must write a function that receives the number of the training data set (input, output) and returns the set. PARAMETERS
o $num_data - The number of training data o $num_input - The number of inputs per training data o $num_output - The number of ouputs per training data o $user_function - The user supplied function with following parameters: o num - The number of the training data set o num_input - The number of inputs per training data o num - The number of ouputs per training dataThe number of inputs per training data The function should return an associative array with keys input and output and two array values of input and output. RETURN VALUES
Returns a train data resource on success, or FALSE on error. EXAMPLES
Example #1 fann_create_train_from_callback example <?php function create_train_callback($num_data, $num_input, $num_output) { return array( "input" => array_fill(0, $num_input, 1), "output" => array_fill(0, $num_output, 1), ); } $num_data = 3; $num_input = 2; $num_output = 1; $train_data = fann_create_train_from_callback($num_data, $num_input, $num_output, "create_train_callback"); if ($train_data) { // Do something with $train_data } ?> SEE ALSO
fann_read_train_from_file(3), fann_train_on_data(3), fann_destroy_train(3), fann_save_train(3). PHP Documentation Group FANN_CREATE_TRAIN_FROM_CALLBACK(3)
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