tcalc: 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/tcalc - from package: tcalc

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

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