---
name: "BN_add_word"
section: "3ssl"
platform: "linux"
package: "openssl"
version: "3.6.5-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/BN_add_word"
---

# BN\_add\_word(3ssl)

arithmetic functions on BIGNUMs with integers

## NAME

BN\_add\_word, BN\_sub\_word, BN\_mul\_word, BN\_div\_word, BN\_mod\_word - arithmetic functions on BIGNUMs with integers

## SYNOPSIS

```
 #include <openssl/bn.h>
 int BN_add_word(BIGNUM *a, BN_ULONG w);
 int BN_sub_word(BIGNUM *a, BN_ULONG w);
 int BN_mul_word(BIGNUM *a, BN_ULONG w);
 BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w);
 BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w);
```

## DESCRIPTION

These functions perform arithmetic operations on BIGNUMs with unsigned integers. They are much more efficient than the normal BIGNUM arithmetic operations.

**BN\_add\_word()** adds **w** to **a** (`"a+=w"`).

**BN\_sub\_word()** subtracts **w** from **a** (`"a-=w"`).

**BN\_mul\_word()** multiplies **a** and **w** (`"a*=w"`).

**BN\_div\_word()** divides **a** by **w** (`"a/=w"`) and returns the remainder.

**BN\_mod\_word()** returns the remainder of **a** divided by **w** (`"a%w"`).

For **BN\_div\_word()** and **BN\_mod\_word()**, **w** must not be 0.

## RETURN VALUES

**BN\_add\_word()**, **BN\_sub\_word()** and **BN\_mul\_word()** return 1 for success, 0 on error. The error codes can be obtained by **ERR\_get\_error**(3).

**BN\_mod\_word()** and **BN\_div\_word()** return **a**%**w** on success and **(BN\_ULONG)-1** if an error occurred.

## SEE ALSO

**ERR\_get\_error**(3), **BN\_add**(3)

## COPYRIGHT

Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License").  You may not use this file except in compliance with the License.  You can obtain a copy in the file LICENSE in the source distribution or at \<https://www.openssl.org/source/license.html\>.