concalc: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/concalc - from package: concalc

You may install the required package with command apt-get install {package}

Error in other languages:
concalc: bevel nie gevind nie
concalc: comandă negăsită
concalc: comando não encontrado
concalc: commande introuvable
concalc: command not found
concalc: käsku ei ole
concalc: không tìm thấy lệnh
concalc: komanda nerasta
concalc: Kommando nicht gefunden.
concalc: kommandot finns inte
concalc: komut yok
concalc: nie znaleziono polecenia
concalc: níor aimsíodh an t-ordú
concalc: no se encontró la orden
concalc: no s'ha trobat l'ordre
concalc: opdracht niet gevonden
concalc: parancs nem található
concalc: perintah tidak ditemukan
concalc: príkaz nenájdený
concalc: příkaz nenalezen
concalc: команда не найдена
concalc: командата не е открита
concalc: 命令找不到
concalc: コマンドが見つかりません