why should i use :std::: everytime?

[mdsiaofficial]

some other codes/other websites, I found they don't use "std::". instead, some of them said that "using namespace std" after header filer is replacing this "std::".
is this a good practice to use the "std::" every time?

[Manoffsteel]

i think no

[dluffy121]

@mdsiaofficial
It's about good practice, for a simple project like this where the purpose is to just experiment its fine to use "using namespace ". But for larger projects usage of this is not recommended, as it may get confusing if the included headers files also have them.

Example:

// temp.cpp

#include <iostream>
using namespace std;

void something()
{
    cout << "something" << endl;
}

// main.cpp

#include "temp.cpp"

void cout()
{
    // to confuse
}

int main()
{
    std::cout << "doing something" << std::endl;  // will work fine as we explicitly mention the namepsace "std"
    cout << "will get confused now" << endl;  // compile error will get confused
    cout();  // compile error will get confused
    something();
    return 0;
}

Although you can avoid this by putting temp.cpp code into a namespace temp and in main cpp create a "using namepace " for it, but then the cycle may repeat for someone trying to include main.cpp