Hi i am new to qt but i have programing experience in c++ in dev - c++
after i moved to qt i thought i could start like this if i press a button it should output hello world it is just showing me 1 error system was not declared in the scope

>> error system was not declared in the scope

If the code involves a call to system(), then you need to #include <cstdlib> .

You probably don't need system if it's a GUI application, as clicking the button to display hello world shouldn't close the window unless you explicitly tell it to.