MATLAB: Can anybody help in understanding fopen and fread

Question

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.

Answer 1

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.