# @stdlib/constants-float64-high-word-significand-mask

> High word mask for the significand of a double-precision floating-point number.

Latest version **0.2.3** (published 2026-02-07) · Apache-2.0 license · 0 weekly downloads

## Install

```sh
npm install @stdlib/constants-float64-high-word-significand-mask
pnpm add @stdlib/constants-float64-high-word-significand-mask
yarn add @stdlib/constants-float64-high-word-significand-mask
bun add @stdlib/constants-float64-high-word-significand-mask
```

## Health

**Score 55/100 (C)** — status: stable.

Positive: has types; no vulnerabilities; high maintenance score.

Warnings: low downloads; no esm support; pre 1.0.

## Facts

| | |
|---|---|
| Version | 0.2.3 |
| Published | 2026-02-07 |
| First published | 2021-06-14 |
| Weekly downloads | 0 |
| License | Apache-2.0 |
| TypeScript types | bundled |
| Module format | CommonJS |
| Node | >=0.10.0 |
| Dependencies | 0 |
| Unpacked size | 26.7 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 1 |
| Author | The Stdlib Authors |
| Maintainers | stdlib-bot, kgryte, planeshifter, rreusser |
| Keywords | stdlib, stdmath, constant, const, mathematics, math, float, float64, 64bit, floating-point, ieee754, mask, significand, bits, high, word |

## Links

- npm: https://www.npmjs.com/package/@stdlib/constants-float64-high-word-significand-mask
- Repository: https://github.com/stdlib-js/constants-float64-high-word-significand-mask
- Homepage: https://stdlib.io
- Issues: https://github.com/stdlib-js/stdlib/issues
- Funding: https://opencollective.com/stdlib
- npm.io page: https://npm.io/package/@stdlib/constants-float64-high-word-significand-mask

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## Recent versions

- 0.2.3 (latest) — 2026-02-07
- 0.2.2 — 2024-07-27
- 0.2.1 — 2024-02-22
- 0.2.0 — 2024-02-14
- 0.1.1 — 2023-10-04
- 0.1.0 — 2023-09-23
- 0.0.8 — 2022-11-03
- 0.0.7 — 2022-02-16
- 0.0.6 — 2021-08-22
- 0.0.5 — 2021-07-06
- 0.0.4 — 2021-06-27
- 0.0.3 — 2021-06-16
- 0.0.2 — 2021-06-15
- 0.0.1 — 2021-06-14

## README

<!--

@license Apache-2.0

Copyright (c) 2018 The Stdlib Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

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  <summary>
    About stdlib...
  </summary>
  <p>We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.</p>
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</details>

# FLOAT64_HIGH_WORD_SIGNIFICAND_MASK

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> High word mask for the significand of a [double-precision floating-point number][ieee754].

<section class="installation">

## Installation

```bash
npm install @stdlib/constants-float64-high-word-significand-mask
```

</section>

<section class="usage">

## Usage

<!-- eslint-disable id-length -->

```javascript
var FLOAT64_HIGH_WORD_SIGNIFICAND_MASK = require( '@stdlib/constants-float64-high-word-significand-mask' );
```

#### FLOAT64_HIGH_WORD_SIGNIFICAND_MASK

High word mask for the significand of a [double-precision floating-point number][ieee754].

<!-- eslint-disable id-length -->

```javascript
// 0x000fffff = 1048575 => 0 00000000000 11111111111111111111
var bool = ( FLOAT64_HIGH_WORD_SIGNIFICAND_MASK === 0x000fffff );
// returns true
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   The higher order word of a [double-precision floating-point number][ieee754] is a 32-bit integer containing the more significant bits which include the exponent and sign.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint-disable id-length -->

<!-- eslint no-undef: "error" -->

```javascript
var getHighWord = require( '@stdlib/number-float64-base-get-high-word' );
var FLOAT64_HIGH_WORD_SIGNIFICAND_MASK = require( '@stdlib/constants-float64-high-word-significand-mask' );

var x = 11.5;
var hi = getHighWord( x ); // 0 10000000010 01110000000000000000
// returns 1076297728

// Mask off all bits except for the significand bits:
var out = hi & FLOAT64_HIGH_WORD_SIGNIFICAND_MASK; // 0 00000000000 01110000000000000000
// returns 458752

// Mask on the significand bits and leave other bits unchanged:
out = hi | FLOAT64_HIGH_WORD_SIGNIFICAND_MASK; // 0 10000000010 11111111111111111111
// returns 1076887551
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/constants/float64/high_word_significand_mask.h"
```

#### STDLIB_CONSTANT_FLOAT64_HIGH_WORD_SIGNIFICAND_MASK

Macro for the high word mask for the significand of a [double-precision floating-point number][ieee754].

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/constants-float64/high-word-exponent-mask`][@stdlib/constants/float64/high-word-exponent-mask]</span><span class="delimiter">: </span><span class="description">high word mask for the exponent of a double-precision floating-point number.</span>
-   <span class="package-name">[`@stdlib/constants-float64/high-word-sign-mask`][@stdlib/constants/float64/high-word-sign-mask]</span><span class="delimiter">: </span><span class="description">high word mask for the sign bit of a double-precision floating-point number.</span>
-   <span class="package-name">[`@stdlib/constants-float64/high-word-abs-mask`][@stdlib/constants/float64/high-word-abs-mask]</span><span class="delimiter">: </span><span class="description">high word mask for excluding the sign bit of a double-precision floating-point number.</span>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->


<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

<!-- /.stdlib -->

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<section class="links">

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[npm-url]: https://npmjs.org/package/@stdlib/constants-float64-high-word-significand-mask

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[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/constants-float64-high-word-significand-mask/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/constants-float64-high-word-significand-mask?branch=main

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[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules

[deno-url]: https://github.com/stdlib-js/constants-float64-high-word-significand-mask/tree/deno
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[esm-url]: https://github.com/stdlib-js/constants-float64-high-word-significand-mask/tree/esm
[esm-readme]: https://github.com/stdlib-js/constants-float64-high-word-significand-mask/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/constants-float64-high-word-significand-mask/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/constants-float64-high-word-significand-mask/main/LICENSE

[ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985

<!-- <related-links> -->

[@stdlib/constants/float64/high-word-exponent-mask]: https://www.npmjs.com/package/@stdlib/constants-float64-high-word-exponent-mask

[@stdlib/constants/float64/high-word-sign-mask]: https://www.npmjs.com/package/@stdlib/constants-float64-high-word-sign-mask

[@stdlib/constants/float64/high-word-abs-mask]: https://www.npmjs.com/package/@stdlib/constants-float64-high-word-abs-mask

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---
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