calc: 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/calc - from package: apcalc

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

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