Description
Return low boundaries of one-bit runs.
Bit positions are usually counted from the least-significant bit, while a displayed binary string has its own left-to-right indexing convention. Masks, fields and parity predicates describe a selected region or pattern; local agreement does not validate a complete encoded record.
Return low boundaries of one-bit runs.
When to use this tool
Use Bitmask Run Start Boundary Mask when checking the stated mask, field, parity or bit-index convention.
How to use the tool and how it works
- Enter word, width. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read mask. Use the output convention below.
Return low boundaries of one-bit runs. Require width 1..128 and bounded word; output mask = word AND NOT(word shifted left one), truncated to width.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| word | Word | Required. Text; maximum UTF-16 length 8192. Integer syntax: optional + or - and 1-128 decimal digits; leading zeros accepted. Apply the sign restriction above. |
| width | Width under the stated bit, interval or geometry convention; apply the field-specific units and bounds. | Required. Safe integer; minimum 1; maximum 128. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| mask | Mask | Required. Text; maximum UTF-16 length 8192. |
{
"input": {
"word": "28",
"width": 8
},
"output": {
"mask": "4"
}
}Limitations and assumptions
- Set bits mark each run's least-significant end; no textual left/right convention or byte order is inferred.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Choose an explicit bit order, word width and missing-position policy; use the complete record format and appropriate parsing or checksum methods for full validation.
References
Similar or alternative tools
- Bitmask Run End Boundary Mask
Return high boundaries of one-bit runs.
- Bitmask Trailing Run Fill
Fill low bits through the least-significant set bit.