# What is the proper term for the position of a digit within a number?

I am writing documentation for a code base, and I want my documentation to be as clear and unambiguous as possible. I am searching for the proper term to refer to the position of digit within a number.

Take the number, 00100000, and I want to refer to the position of the 1. So far I have come up with bit "placement"; however, this is unclear as to which direction the bit placement increases, without further explanation. I know that the leading bit is referred to as the "most significant bit", and the rightmost is referred to as the "least significant bit"; therefore, would it make sense to use the term bit "significance", or is there a mathematical term to describe this?

Example of how I plan to use the term: The placement of the 1 is 5, or the significance of the 1 is 5.

• 1st, 2nd, 3rd, 4th....digit or 1st, 2nd ... significant bit? Commented Jan 31, 2017 at 23:49
• @Chris I am looking a term that doesn't refer to specific digit, rather a term used to describe any of the digits Commented Feb 1, 2017 at 0:02
• Ordinal number - a number denoting relative position in a sequence, such as first, second, third, etc... Commented Feb 1, 2017 at 0:11
• I think you should direct this to a mathematics site. This isn't purely a English Language question but rather a mathematics or maybe computer related question. General terms will depend on the base of the number used. For example, binary (base 2) will use bit whereas octal (base 8) or hexadecimal (base 16) would use byte. All bases can use digit Commented Feb 1, 2017 at 0:17
• @Chris General terms are general: they do not depend on the base of the number used. Commented Feb 1, 2017 at 0:24

## 2 Answers

In a positional numeral system, each digit's weight is determined by its position in the numeral.

• I didn't realize position was the technical term for it. I appreciate the links to read more into it. Commented Feb 1, 2017 at 0:12

This is as much as a computer science question as an English language one. Bit positions in a numeric word have confusing aspects. We read from left to right, but bits are numbered from right to left. Plus, the lowest order bit is referred to as "bit 0", not "bit 1". So it is not innately clear to English speakers in general whether the "fifth" bit is the 5th from the right or 5th from the left. Even programmers can get confused, especially the newer "kids" who are often taught high level languages without a base knowledge of hardware or even assembly language.

Now to the question itself. I would approach it in one of two ways. If I knew the documentation should be read from start to finish, then I would include a short section at the front with a drawing of a numeric word and its bits, and explain that bit 0 is on the right, bit 1 is next to it, etc. The drawing could show all of this. Then in the rest of the document, just refer to "bit 7" or "bit 23" as if the reader would know what you mean. Another common technical form is that "bit 0" is the 1-bit, "bit 1" is the 2-bit, "bit 4" is the 16-bit, etc. So: The 1 is at bit 5.

If the document is likely to be accessed at random locations, not actually read from start to finish, then for clarity's sake, be clear. Say "the fifth bit from the right" or the "seventh bit from the left", whatever will make it easier for the reader to follow at that particular spot. So: The 1 is at the sixth bit from the right.

htmlcoderexe's comment to this answer got me doing a little more research. The term you are looking for may be bit numbering. Unfortunately this term opens a whole new can of worms - LSB Bit 0 numbering vs MSB Bit 0 numbering. My whole discussion above was based on the former, because I was thinking of a numeric word as a stand-alone number, not at how a specific piece of hardware might store that number. (If nothing else, the Wiki article contains public domain illustrations of bit positions you could use in your document.)

• While not answering the question as worded (the proper term), this is some useful insight, establishing a convention and following it would add a lot to readability of documentation. Commented Feb 1, 2017 at 0:58
• @htmlcoderexe I guess I have a bad habit of reading between the lines and answering what I think the questioner wanted to know rather replying to the exact wording. 🤠 I'm not sure there even is an accepted, clear, and unambiguous term for the position of a bit within a numeric word. // Regarding "establishing a convention", I agree, which would tend to favor my first approach, "bit 3". Commented Feb 1, 2017 at 1:31
• @htmlcoderexe Okay, I think I may have found the term and extended my answer to include it. Thank you for the polite RTFQ reminder. Commented Feb 1, 2017 at 1:44
• And is bit 0 the first bit or the zeroth bit? There's often a preference within a tradition but there isn't a universal answer. Commented Feb 1, 2017 at 13:00