Abakus is a simple calculator for KDE, based on a concept of Roberto Alsina's. Think of it as bc (the command-line calculator) with a nice GUI.

Abakus wasn't the only calculator to be developed due to Roberto's brainstorm. You may also want to try Ariya Hidayat's SpeedCrunch (maintained/improved by Johan Thelin). In fact many of Abakus's user interface niceties were donated from SpeedCrunch.

Important note: Although I actually still use abakus from time to time, it has fallen far to the back of my list of "maintained software packages". I have uploaded a version (0.92) that builds for KDE 4 based on occasional requests I receive by email, but you should consider feature development stopped for now (unless someone else picks it up). For instance, I have not updated the screenshots (not that it's substantially different now).

Latest version is 0.92, which had the following changes from 0.91:

• Better KDE 4 support, including use of the standard KDE 4 build system.
• More bugs (sorry).

Some of its features include:

• Keyboard accessible.
• User-defined functions.
• Includes an RPN mode for old-school calculator users.
• Includes a scrollable history window, which can be hidden for compactness. When the history pane is hidden, results are shown directly in the edit line.
• Previous expressions can be entered using the up and down keys.
• Built-in functions, including a full suite of trigonometric, logarithmic, and exponential functions.
• Fully supports KDE, so it supports KDE features automatically, including some automatic DCOP support.
• The calculator supports using variables (which are saved between different runs).
• Automatic parentheses closing.
• Includes predefined values of pi and the natural exponential base (e).
• The last successful answer is stored in the variable ans.
• Compiled in C++ for fast startup speed.
• Both ^ and ** are supported for exponentiation.
• Exponentiation is (correctly) right-associative. What this means is that 2 ^ 3 ^ 2 returns 512 instead of 64.
• Expressions like 3 + -2 are accepted, instead of requiring a separate sign-inversion symbol like the TI family of calculators.

abakus in compact mode entering an expression (with the Result tooltip shown):

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You can download it here: abakus-0.92.tar.bz2 (276K)

SHA256 sums:

9c873307bdcc8ab06a73de8bbc80fa933bf58ed64d3e1958f46635b61df39c5d  abakus-0.92.tar.bz2

Older versions:
abakus-0.91.tar.bz2 (372K)
abakus-0.90.tar.bz2 (367K)
abakus-0.85.tar.bz2 (322K)
abakus-0.80.2.tar.bz2 (128K)
abakus-0.76.tar.bz2 (55K)
abakus-0.75.tar.bz2 (53K)
abakus-0.70.tar.bz2 (51K)
abakus-0.61.tar.bz2 (44K)
abakus-0.60.tar.bz2 (37K)

SHA1 sums:

c08b2db5920418d38813f3947530d9f17c72bf0a  abakus-0.91.tar.bz2
cec68da3edbaa590bbdc6ac960b10c0878ce0d75  abakus-0.90.tar.bz2
d0a40c5ece3b143ad8f7e0b59a8a91fdcae0318d  abakus-0.85.tar.bz2
b6517228b85d56c50f99f56ed7178f47663c781f  abakus-0.80.2.tar.bz2
5926389cb1ca3b3959bbc526f133e8d16b28045e  abakus-0.76.tar.bz2
da7017042f2d911016597801f357f47cbbec3e56  abakus-0.75.tar.bz2
40f5413239cf04d1fa3f883510282de6149d461b  abakus-0.70.tar.bz2
1434ddb3ad6f18ef3819f0d05c84a7a756cfd285  abakus-0.61.tar.bz2
e56f7a162e9d61898d5332e8b6377b86d151bb72  abakus-0.60.tar.bz2

MD5 sums:

56eaa5d98caa96973c09d62ae7da3061  abakus-0.91.tar.bz2
7b86a467de78108840a8c37277a12f0e  abakus-0.90.tar.bz2
b66fafc26c72c0911c21674a1ec46777  abakus-0.85.tar.bz2
4edfdf6982eebea11c1c83292edd0dc7  abakus-0.80.2.tar.bz2
9524fa1eeae5063af572c22d15052a79  abakus-0.76.tar.bz2
17c23c3f33fb9a686d6753cf08128eb1  abakus-0.75.tar.bz2
c80199d153c34d3a1bbbd444c9fbacfc  abakus-0.70.tar.bz2
d2b5cc349f02570dae53ea345d3a344e  abakus-0.61.tar.bz2
bf8f174706695a367c335c04571e94f4  abakus-0.60.tar.bz2

Notes:

• You need flex and bison installed to build the program, as I've not included the generated sources with the package.
• On the other hand, although the MPFR library is (still!) supported, it is not required.