[#BN_num_bits]
= BN&lowbar;num&lowbar;bits
:mrdocs:

Return the size of `a` in bits (index of the highest set bit plus one)&period;

== Synopsis

Declared in `&lt;openssl&sol;bn&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
BN&lowbar;num&lowbar;bits(xref:BIGNUM.adoc[BIGNUM] const* a);
----

== Return Value

Number of significant bits in the absolute value of `a&period;`

== Parameters

[cols="1,4"]
|===
| Name| Description
| *a*
| BIGNUM to measure&semi; zero yields 0&period;
|===


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