QCCalculator: 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/QCCalculator - from package: topp

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

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