RK: Cell Value, RK Number (7Eh)

Microsoft Excel uses an internal number type, called an RK number, to save memory and disk space.

Record Data

Offset	Name	Size	Contents

4	rw	2	Row number
6	col	2	Column number
8	ixfe	2	Index to the XF record that contains the cell format
10	rk	4	RK number (see the following description)

An RK number is either a 30-bit integer or the most significant 30 bits of an IEEE number. The two LSBs of the 32-bit rk field are always reserved for RK type encoding; this is why the RK numbers are 30 bits, not the full 32. See the following diagram.

There are four different RK number types, as described in the following table.

RK type	Encode priority	Number (decimal)	RK number (hex)	Description of 30-bit encoding

0	1	1	3F F0 00 00	IEEE number
1	3	1.23	40 5E C0 01	IEEE number x 100
2	2	12345678	02 F1 85 3A	Integer
3	4	123456.78	02 F1 85 3B	Integer x 100

Microsoft Excel always attempts to store a number as an RK number instead of an IEEE number. There is also a specific priority of RK number encoding that the program uses. The following flowchart is a simplified version of the encoding algorithm. The algorithm always begins with an IEEE (full 64-bit) number.

You can use the following C code to demonstrate how to decode RK numbers:

double NumFromRk(long rk)
    {
    double num;
    if(rk & 0x02)
        {
        // int
        num = (double) (rk >> 2);
        }

    else
        {
        // hi words of IEEE num
        *((long *)&num+1) = rk & 0xfffffffc;
        *((long *)&num) = 0;
        }
    if(rk & 0x01)
        // divide by 100
        num /= 100;
    return num;
    }
main()
    {
    printf("%f\n", NumFromRk (0x02f1853b));
    }

If you write a NUMBER record to a BIFF file, Microsoft Excel may convert the number to an RK number when it reads the file.