can anybody help in understanding fopen and fread?

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subha
subha 2014-6-20
评论： subha 2014-6-30
As per my understanding, fopen open the file in a mode which we want. For example, if we say r,then it opens in read mode. fread, read the open file and returns the no of elements.
Based on above line, i tried below code.
f= fopen('train-images-idx3-ubyte', 'r')
Ans:
f =
56
Here what 56 represents? I understand it is file identifier. How it is generated?
[a, count]= fread(f,4,'int 32')
a =
1.0e+09 *
0.0509
1.6259
0.4698
0.4698
count =
4
Could anybody help me to understand the above result.

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采纳的回答

Image Analyst
Image Analyst 2014-6-20
f is some identification number of the file. Don't worry about what it's actual value is or how it's generated - it doesn't matter (as long as it's not -1 which indicates an error). It's simply used to tell fread() or fprintf() what file to talk to.
The fread line read four 4-byte integers from the binary file. You store them into variable "a". It should be 'int32' rather than 'int 32' though.
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Marta Salas
Marta Salas 2014-6-20
The file identifier is a integer greater than 3. Identifier -1 means fopen can not open the file, and MATLAB reserves file identifiers 0, 1, and 2 for standard input, standard output (the screen), and standard error, respectively.
[a, count]= fread(f,4,'int 32')
This line is reading 4 values in the file f such that the source data is class uint32. Then the 4 values are stored in a and the number of values read from the file is stored in count

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