Bug: 144699509

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  1. 64cab7f Upgrade bc to 6.6.1 am: 306341a225 am: cdb14c26d9 am: 9e6368af49 am: 64707ec357 am: baba618c37 by Elliott Hughes · 7 months ago main master
  2. baba618 Upgrade bc to 6.6.1 am: 306341a225 am: cdb14c26d9 am: 9e6368af49 am: 64707ec357 by Elliott Hughes · 7 months ago
  3. 64707ec Upgrade bc to 6.6.1 am: 306341a225 am: cdb14c26d9 am: 9e6368af49 by Elliott Hughes · 7 months ago
  4. 9e6368a Upgrade bc to 6.6.1 am: 306341a225 am: cdb14c26d9 by Elliott Hughes · 7 months ago
  5. cdb14c2 Upgrade bc to 6.6.1 am: 306341a225 by Elliott Hughes · 7 months ago


WARNING: New user registration for https://git.gavinhoward.com/ is disabled because of spam. If you need to report a bug with bc, email gavin at this site minus the git. part for an account, and I will create one for you. Or you can report an issue at GitHub.

WARNING: This project has moved to https://git.gavinhoward.com/ for these reasons, though GitHub will remain a mirror.

This is an implementation of the POSIX bc calculator that implements GNU bc extensions, as well as the period (.) extension for the BSD flavor of bc.

For more information, see this bc's full manual.

This bc also includes an implementation of dc in the same binary, accessible via a symbolic link, which implements all FreeBSD and GNU extensions. (If a standalone dc binary is desired, bc can be copied and renamed to dc.) The ! command is omitted; I believe this poses security concerns and that such functionality is unnecessary.

For more information, see the dc's full manual.

This bc also provides bc's math as a library with C bindings, called bcl.

For more information, see the full manual for bcl.


This bc is Free and Open Source Software (FOSS). It is offered under the BSD 2-clause License. Full license text may be found in the LICENSE.md file.


This bc only requires either:

  1. Windows 10 or later, or
  2. A C99-compatible compiler and a (mostly) POSIX 2008-compatible system with the XSI (X/Open System Interfaces) option group.

Since POSIX 2008 with XSI requires the existence of a C99 compiler as c99, any POSIX and XSI-compatible system will have everything needed.

POSIX-compatible systems that are known to work:

  • Linux
  • FreeBSD
  • OpenBSD
  • NetBSD
  • Mac OSX
  • Solaris* (as long as the Solaris version supports POSIX 2008)
  • AIX
  • HP-UX* (except for history)

In addition, there is compatibility code to make this bc work on Windows.

Please submit bug reports if this bc does not build out of the box on any system.


This bc should build unmodified on any POSIX-compliant system or on Windows starting with Windows 10 (though earlier versions may work).

For more complex build requirements than the ones below, see the build manual.


There is no guarantee that this bc will work on any version of Windows earlier than Windows 10 (I cannot test on earlier versions), but it is guaranteed to work on Windows 10 at least.

Also, if building with MSBuild, the MSBuild bundled with Visual Studio is required.

Note: Unlike the POSIX-compatible platforms, only one build configuration is supported on Windows: extra math and history enabled, NLS (locale support) disabled, with both calculators built.


To build bc, you can open the vs/bc.sln file in Visual Studio, select the configuration, and build.

You can also build using MSBuild with the following from the root directory:

msbuild -property:Configuration=<config> vs/bc.sln

where <config> is either one of Debug or Release.

On Windows, the calculators are built as vs/bin/<platform>/<config>/bc.exe and vs/bin/<Platform>/<Config>/dc.exe, where <platform> can be either Win32 or x64, and <config> can be Debug or Release.

Note: On Windows, dc.exe is just copied from bc.exe; it is not linked. Patches are welcome for a way to do that.

bcl (Library)

To build the library, you can open the vs/bcl.sln file in Visual Studio, select the configuration, and build.

You can also build using MSBuild with the following from the root directory:

msbuild -property:Configuration=<config> vs/bcl.sln

where <config> is either one of Debug, ReleaseMD, or ReleaseMT.

On Windows, the library is built as vs/lib/<platform>/<config>/bcl.lib, where <platform> can be either Win32 or x64, and <config> can be Debug, ReleaseMD, or ReleaseMT.

POSIX-Compatible Systems

On POSIX-compatible systems, bc is built as bin/bc and dc is built as bin/dc by default.


For the default build with optimization, use the following commands in the root directory:

./configure.sh -O3

One Calculator

To only build bc, use the following commands:

./configure.sh --disable-dc

To only build dc, use the following commands:

./configure.sh --disable-bc


For debug builds, use the following commands in the root directory:

./configure.sh -g


To install, use the following command:

make install

By default, bc and dc will be installed in /usr/local. For installing in other locations, use the PREFIX environment variable when running configure.sh or pass the --prefix=<prefix> option to configure.sh. See the build manual, or run ./configure.sh --help, for more details.


To build the math library, pass the -a or --library options to configure.sh:

./configure.sh -a

When building the library, the executables are not built. For more information, see the build manual.

The library API can be found in manuals/bcl.3.md or man bcl once the library is installed.

Package and Distro Maintainers

This section is for package and distro maintainers.

Out-of-Source Builds

Out-of-source builds are supported; just call configure.sh from the directory where the actual build will happen.

For example, if the source is in bc, the build should happen in build, then call configure.sh and make like so:


WARNING: The path to configure.sh from the build directory must not have spaces because make does not support target names with spaces.

Recommended Compiler

When I ran benchmarks with my bc compiled under clang, it performed much better than when compiled under gcc. I recommend compiling this bc with clang.

I also recommend building this bc with C11 if you can because bc will detect a C11 compiler and add _Noreturn to any relevant function(s).

Recommended Optimizations

I wrote this bc with Separation of Concerns, which means that there are many small functions that could be inlined. However, they are often called across file boundaries, and the default optimizer can only look at the current file, which means that they are not inlined.

Thus, because of the way this bc is built, it will automatically be slower than other bc implementations when running scripts with no math. (My bc's math is much faster, so any non-trivial script should run faster in my bc.)

Some, or all, of the difference can be made up with the right optimizations. The optimizations I recommend are:

  1. -O3
  2. -flto (link-time optimization)

in that order.

Link-time optimization, in particular, speeds up the bc a lot. This is because when link-time optimization is turned on, the optimizer can look across files and inline much more heavily.

However, I recommend NOT using -march=native. Doing so will reduce this bc's performance, at least when building with link-time optimization. See the benchmarks for more details.

Stripping Binaries

By default, non-debug binaries are stripped, but stripping can be disabled with the -T option to configure.sh.

Using This bc as an Alternative

If this bc is packaged as an alternative to an already existing bc package, it is possible to rename it in the build to prevent name collision. To prepend to the name, just run the following:

EXECPREFIX=<some_prefix> ./configure.sh

To append to the name, just run the following:

EXECSUFFIX=<some_suffix> ./configure.sh

If a package maintainer wishes to add both a prefix and a suffix, that is allowed.

Note: The suggested name (and package name) when bc is not available is bc-gh.

Karatsuba Number

Package and distro maintainers have one tool at their disposal to build this bc in the optimal configuration: scripts/karatsuba.py.

This script is not a compile-time or runtime prerequisite; it is for package and distro maintainers to run once when a package is being created. It finds the optimal Karatsuba number (see the algorithms manual for more information) for the machine that it is running on.

The easiest way to run this script is with make karatsuba.

If desired, maintainers can also skip running this script because there is a sane default for the Karatsuba number.


This bc is robust.

It is well-tested, fuzzed, and fully standards-compliant (though not certified) with POSIX bc. The math has been tested with 40+ million random problems, so it is as correct as I can make it.

This bc can be used as a drop-in replacement for any existing bc. This bc is also compatible with MinGW toolchains.

In addition, this bc is considered complete; i.e., there will be no more releases with additional features. However, it is actively maintained, so if any bugs are found, they will be fixed in new releases. Also, additional translations will also be added as they are provided.


If I (Gavin D. Howard) get hit by a bus and future programmers need to handle work themselves, the best place to start is the Development manual.

Vim Syntax

I have developed (using other people's code to start) vim syntax files for this bc and dc, including the extensions.

bc Libs

I have gathered some excellent bc and dc libraries. These libraries may prove useful to any serious users.

Comparison to GNU bc

This bc compares favorably to GNU bc.

  • This bc builds natively on Windows.
  • It has more extensions, which make this bc more useful for scripting. (See Extensions.)
  • This bc is a bit more POSIX compliant.
  • It has a much less buggy parser. The GNU bc will give parse errors for what is actually valid bc code, or should be. For example, putting an else on a new line after a brace can cause GNU bc to give a parse error.
  • This bc has fewer crashes.
  • GNU bc calculates the wrong number of significant digits for length(x).
  • GNU bc will sometimes print numbers incorrectly. For example, when running it on the file tests/bc/power.txt in this repo, GNU bc gets all the right answers, but it fails to wrap the numbers at the proper place when outputting to a file.
  • This bc is faster. (See Performance.)


Because this bc packs more than 1 decimal digit per hardware integer, this bc is faster than GNU bc and can be much faster. Full benchmarks can be found at manuals/benchmarks.md.

There is one instance where this bc is slower: if scripts are light on math. This is because this bc's intepreter is slightly slower than GNU bc, but that is because it is more robust. See the benchmarks.


Below is a non-comprehensive list of extensions that this bc and dc have that all others do not.

  • An extended math library. (See here for more information.)
  • A command-line prompt.
  • Turning on and off digit clamping. (Digit clamping is about how to treat “invalid” digits for a particular base. GNU bc uses it, and the BSD bc does not. Mine does both.)
  • A pseudo-random number generator. This includes the ability to set the seed and get reproducible streams of random numbers.
  • The ability to use stacks for the globals scale, ibase, and obase instead of needing to restore them in every function.
  • The ability to not use non-standard keywords. For example, abs is a keyword (a built-in function), but if some script actually defines a function called that, it's possible to tell my bc to not treat it as a keyword, which will make the script parses correctly.
  • The ability to turn on and off printing leading zeroes on numbers greater than -1 and less than 1.
  • Outputting in scientific and engineering notation.
  • Accepting input in scientific and engineering notation.
  • Passing strings and arrays to the length() built-in function. (In dc, the Y command will do this for arrays, and the Z command will do this for both numbers and strings.)
  • The abs() built-in function. (This is the b command in dc.)
  • The is_number() and is_string() built-in functions. (These tell whether a variable is holding a string or a number, for runtime type checking. The commands are u and t in dc.)
  • For bc only, the divmod() built-in function for computing a quotient and remainder at the same time.
  • For bc only, the asciify() built-in function for converting an array to a string.
  • The $ truncation operator. (It's the same in bc and dc.)
  • The @ “set scale” operator. (It's the same in bc and dc.)
  • The decimal shift operators. (<< and >> in bc, H and h in dc.)
  • Built-in functions or commands to get the max of scale, ibase, and obase.
  • The ability to put strings into variables in bc. (This always existed in dc.)
  • The ' command in dc for the depth of the execution stack.
  • The y command in dc for the depth of register stacks.
  • Built-in functions or commands to get the value of certain environment variables that might affect execution.
  • The stream keyword to do the same thing as the P command in dc.
  • Defined order of evaluation.
  • Defined exit statuses.
  • All environment variables other than POSIXLY_CORRECT, BC_ENV_ARGS, and BC_LINE_LENGTH.
  • The ability for users to define their own defaults for various options during build. (See here for more information.)


To see what algorithms this bc uses, see the algorithms manual.


Currently, there is no locale support on Windows.

Additionally, this bc only has support for English (and US English), French, German, Portuguese, Dutch, Polish, Russian, Japanese, and Chinese locales. Patches are welcome for translations; use the existing *.msg files in locales/ as a starting point.

In addition, patches for improvements are welcome; the last two messages in Portuguese were made with Google Translate, and the Dutch, Polish, Russian, Japanese, and Chinese locales were all generated with DeepL.

The message files provided assume that locales apply to all regions where a language is used, but this might not be true for, e.g., fr_CA and fr_CH. Any corrections or a confirmation that the current texts are acceptable for those regions would be appreciated, too.

Other Projects

Other projects based on this bc are:

  • busybox bc. The busybox maintainers have made their own changes, so any bugs in the busybox bc should be reported to them.
  • toybox bc. The maintainer has also made his own changes, so bugs in the toybox bc should be reported there.
  • FreeBSD bc. While the bc in FreeBSD is kept up-to-date, it is better to report bugs there, as well as submit patches, and the maintainers of the package will contact me if necessary.
  • Mac OSX bc. Any bugs in that bc should be reported to me, but do expect bugs because the version is old.
  • Android Open Source bc. Any bugs in that bc can be reported here.

This is a non-comprehensive list of Linux distros that use this bc as the system bc:

Other Linux distros package it as a second-class alternative, usually as bc-gh or howard-bc.


This bc is written in pure ISO C99, using POSIX 2008 APIs with custom Windows compatibility code.

Commit Messages

This bc uses the commit message guidelines laid out in this blog post.

Semantic Versioning

This bc uses semantic versioning.


This repository is 100% AI-Free code.


Items labeled with (maintainer use only) are not included in release source tarballs.


.gitignore           The git ignore file (maintainer use only).
.gitattributes       The git attributes file (maintainer use only).
bcl.pc.in            A template pkg-config file for bcl.
configure            A symlink to configure.sh to make packaging easier.
configure.sh         The configure script.
LICENSE.md           A Markdown form of the BSD 2-clause License.
Makefile.in          The Makefile template.
NEWS.md              The changelog.
NOTICE.md            List of contributors and copyright owners.


benchmarks  A folder of benchmarks for various aspects of bc performance.
gen         The bc math library, help texts, and code to generate C source.
include     All header files.
locales     Locale files, in .msg format. Patches welcome for translations.
manuals     Manuals for both programs.
src         All source code.
scripts     A bunch of shell scripts to help with development and building.
tests       All tests.
vs          Files needed for the build on Windows.