The structure NxCategoryField is defined in NxCoreAPI.h as:

struct NxCategoryField {
    const char*   FieldName;
    const char*   FieldInfo;
    unsigned char Set;
    unsigned char FieldType;
    unsigned char alignment[6];

    union { // field is ONE of the following depending on 'FieldType' member.
        __int64         i64Bit;          // FieldType == NxCFT_64BIT      (1)
        int             i32Bit;          // FieldType == NxCFT_32BIT      (2)
        const char*     StringZ;         // FieldType == NxCFT_STRINGZ    (3)
        double          Double;          // FieldType == NxCFT_DOUBLE     (4)
        NxPrice         nxPrice;         // FieldType == NxCFT_PRICE      (5)
        NxDate          nxDate;          // FieldType == NxCFT_DATE       (6)
        NxTime          nxTime;          // FieldType == NxCFT_TIME       (7)
        NxString*       pnxString;       // FieldType == NxCFT_NxSTRING   (8)
        StringTableItem stringTableItem; // FieldType == NxCFT_STRING_IDX (9) or NxCFT_STRING_MAP (10)
    } data;


A null-terminated ASCII string for the name of the field.


Contains any comments about the field, may be empty


Has the value 1 if the field has valid data. The value 0 means the data member is not present.

It is important to note that some categories come through more than once per day. These categories might not contain data in every field, so it is imperative to check the "Set" flag to prevent clearing/modifying data unneccessarily.

For more information on the "Set" flag, review the NxMSG_CATEGORY documentation.


Indicates which union member to use to interpret the data. Each field will be one of the following types:

# Field #define Type Name Comment
1 NxCFT_64BIT __int64 i64Bit Used mostly for Total Volume and fields that may exceed 32 bits
2 NxCFT_32BIT int i32Bit Very common. Used for most numbers that are not prices.
3 NxCFT_STRINGZ const char* StringZ null-terminated ASCII string. Used for Company Names, etc.
4 NxCFT_DOUBLE double Double Currently, not used for any field in any category.
5 NxCFT_PRICE NxPrice nxPrice A simple structure containing a 32 bit price with the decimal place indicated by PriceType.
6 NxCFT_DATE NxDate nxDate The structure NxDate used for expiration dates, dividend/split dates, etc.
7 NxCFT_TIME NxTime nxTime The structure NxTime used for last trade time, quote times, etc.
8 NxCFT_NxSTRING NxString* pnxString A pointer to an NxString. Used mostly by Options for a direct link to the underlying.
9 NxCFT_STRING_IDX StringTableItem stringTableItem The structure StringTableItem which indicates the table, and index for a defined string.
10 NxCFT_STRING_MAP StringTableItem stringTableItem Same as NxCFT_STRING_IDX, but index is a series of 32 bits, one for each string in a defined table.


Union of all possible values, selected by FieldType.


For example of category usage see here