National Instruments 320682C

Chapter 2 Formatting and I/O Library

Real Array to Binary File, Assuming a Variable Number of Elements

void StoreArray (double x[], int count, char filename[])

{int file_handle;

file_handle = OpenFile (filename, 2, 0, 0);

FmtFile (file_handle, "%*f<%*f", count, count, x);

CloseFile (file_handle);

}

Remarks

This example shows how a function can be used to write an array of real numbers to a binary file.

The function's parameters are a real array, the number of elements to be written, and the

filename.

The FmtFile call writes the first count elements of x to a file in binary form. The two

asterisks (*) in the format string are matched to count. For instance, if count is 100, then the

format string is equivalent to %100f<100f.

A Variable Portion of a Real Array to a Binary File

void StoreSubArray (double x[], int start, int count, char filename[])

{int file_handle;

file_handle = OpenFile (filename, 2, 0, 0);

FmtFile (file_handle, "%*f<%*f[i*]", count, count, start, x);

CloseFile (file_handle)

}

Remarks

This example is an extension of the previous example. The function also writes a variable

number of elements of a real array to a file. Instead of beginning at the first element of the array,

a starting index is passed to the function.

The FmtFile call writes count elements of x, starting from x[start], to a file in binary

form. The first two asterisks (*) in the format string are matched to count. The third asterisk

is matched to start. For instance, if count is 100 and start is 30, then the format string is

equivalent to %100f<100f[i30]. Because the i modifier specifies a zero-based index into

the real array, the array elements from x[30] through x[129] are written to the file.