c44: 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 CentOS possible default full paths are:

/usr/bin/c44 - from package: djvulibre

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/c44 - from package: djvulibre-bin

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

Error in other languages:
c44: bevel nie gevind nie
c44: comandă negăsită
c44: comando não encontrado
c44: commande introuvable
c44: command not found
c44: käsku ei ole
c44: không tìm thấy lệnh
c44: komanda nerasta
c44: Kommando nicht gefunden.
c44: kommandot finns inte
c44: komut yok
c44: nie znaleziono polecenia
c44: níor aimsíodh an t-ordú
c44: no se encontró la orden
c44: no s'ha trobat l'ordre
c44: opdracht niet gevonden
c44: parancs nem található
c44: perintah tidak ditemukan
c44: príkaz nenájdený
c44: příkaz nenalezen
c44: команда не найдена
c44: командата не е открита
c44: 命令找不到
c44: コマンドが見つかりません