Using Unix 'desk calculator'

dc (also known as /usr/bin/dc or as the Unix desk calculator) is definitely the most useful command you can find on a Unix system. I can't imagine a single working day without using dc (especially with one dollar being (roughly) 6.2931236763 French Francs).

How desesperate I was when I discovered that dc doesn't work correctly on SunOS 5.6!

Just try a simple division like, say, 1083221002471 / 999927. On a SunOS 5.6 workstation, I obtain 1083301. On a SunOS 4 machine or a linux machine, I obtain 1083300, which is the correct answer. I have other examples of incorrect divisions, but this is the smallest one (!). Don't ask me how I found it...

Another problem with dc is that it sometimes refuses to write ASCII codes greater than 99 with the P command, especially on SunOS systems (including SunOS 4). I don't know if it is a bug (since I don't know exactly what the P command is supposed to do), but I think 99 is a pretty strange limit... In any case, it prints those characters correctly on a Silicon Graphics computer (free ad) and on my linux machine (another free ad).

To test your version of dc, try to type in:

  dc

  3808936911278909389359514998203616329962227439192148[d256%P256/d0<.]ds.x

  970313512859254401102697436301630872058487784302540104[d256%P256/d0<.]ds.x

If your dc is able to print ASCII characters over 99, you can try this one. Be sure to type a single line (here is a file with that line; you can download it and try "dc < file" instead):

  22208085721160815839326341402121883690522320029255552164456082082121507399131784888796775404393238740752073581292176033192975608648980579511790754074629932624904826033926771561352802702304711849306991432140783663141097741410673769879986682209343466281135283290275369909264160273176470124389744289584917009576579173596679560702849116170806711176042540325188738564140628164804618257135693047847192850818282310363304691273054958318318136191456275934310979155326791959077883445003166261104834773132040707456928546349673980840313948708349674193786434159922651000968311352206702569130007195445654084933953345626389764219705628257612293204376976748352217929337471880882231223685405877498688770919610871973453341673913923792234893241993439245115105190893660465508673064373840268054184063151225377582060655786260788736204677135397194609418373902725670020397378638535454535982247377168952102335040177207305844444366209308523996849245976720417612176719067483022960817121007244452665449784273243174997760034496193814960150784537785113589011725985900508524882770853637523676303240173952011467376200157457202234158542518689678707600958087139914974630505378072055818423497887022672894966264722482896163204923500950712750800537457664585469095374214293974296229117403664516032413259929513310658563843081832487569416683206341446732898062734501513714984552459725473478529038715898310732843126214088302700527765333188909878114118156328607905954179948741014531467629112351746391357169021505149742077359053197219166630939696390194435167157513452231104227665811363415438461304936968404285629177347016678518931947203796484167545101613670772251307345495413035233907657705241691280430994746768012380728375146653630623831838222282318165089162386341671976737726353273451886027886364291170031129520721957416004799824490011955162466021287535364309928388542132049900161052116530089934228815775998215778916104959359698408064987438386886161480778575982275751968826631954742887974749292068020577501261842082809483702986629865701617200056158514119921272726266484084142349717069035717802916618873448175705514451223911583066310022020808646584937752763866798004057371097500872885733222570967153949159920525516838117787583988167897342360101235912871520761154734770678309671549603175730098764310659277164535040418340982101759825495735066065501823775306294622701628580346350888711132078451931296748345416719473558304071712[d256%P256/d0<.]ds.x

And that's how dc can recite poetry...

Can you guess what this dc program is doing? (There should be an International Obfuscated DC Code Contest...)

  2p3p[dl!d2+s!%0=@l!l^!<#]s#[s/0ds^]s@[p]s&[ddvs^3s!l#x0<&2+l.x]ds.x

But dc can also be useful. For instance:

  echo "$1[p]s2[lip/dli%0=1dvsr]s12sid2%0=13sidvsr[dli%0=1lrli2+dsi!>.]ds.xd1<2" | dc

Michel Charpentier <>