I/O Format Specifiers for Readings IEEE 488.2 Binary Blocks

IEEE Binary Block Data -- %b

An array argument formatted as an IEEE definite-length binary block has a format specifier of the following form:

%[*] [array size] [$S] [b | h | l | I | z | Z] b

Modifier	Interpretation
Default Functionality	The data block received must be in IEEE 488.2 definite-length binary block form.
* (asterisk)	An asterisk acts as the assignment suppression character. The input is scanned but not assigned to any parameters and is discarded.
array size	Specifies the maximum number of elements to read from the device. If the argument is a SAFEARRAY, then the array size may be omitted. A # may be present in lieu of an integer array size modifier, in which case an extra int argument supplies the value.
$S	The argument is assumed to be a SAFEARRAY.
length modifier	If no length modifier is specified, then the argument is assumed to be an array (or SAFEARRAY if $S is used) of BYTE (8-bit) integer. b - argument is an array of BYTE (8-bit) integer. h - argument is an array of short (16-bit) integer. The array size indicates the number of 16-bit words, rather than the number of bytes. As per the 488.2 binary block standard, the data is assumed to have big-endian byte ordering. Byte-swapping is automatically performed on all elements in the array. l - argument is an array of long (32-bit) integer. The array size indicates the number of 32-bit words, rather than the number of bytes. As per the 488.2 binary block standard, the data is assumed to have big-endian byte ordering. Byte-swapping is automatically performed on all elements in the array. I - argument is an array of __int64 (64-bit) integer. The array size indicates the number of 64-bit words, rather than the number of bytes. As per the 488.2 binary block standard, the data is assumed to have big-endian byte ordering. Byte-swapping is automatically performed on all elements in the array. z - argument is an array of float (32-bit) floating-point numbers. The numbers are assumed to be in IEEE 754 format. Z - argument is an array of double (64-bit) floating-point numbers. The numbers assumed to be in IEEE 754 format.

Example -- Definite-length blocks

C++

Copy

HRESULT hr = S_OK;

short rgData[100];

// IEEE definite-length block of 100 16-bit words
hr = io.Scanf(_T("%100hb"), rgData);            

SAFEARRAY* psa = NULL;

// Definite-length block of doubles.  Argument is a SAFEARRAY.
// No field width is needed as Scanf allocates the SAFEARRAY memory
hr = io.Scanf(_T("%$Zb"), &psa);          

// ... use SAFEARRAY result

// IMPORTANT: SAFEARRAY must be destroyed
hr = ::SafeArrayDestory(psa);

Other Resources

Scanf