\documentclass{standalone}

\usepackage{tikz}
\usetikzlibrary{calc}
\begin{document}
   \begin{tikzpicture}[scale=4]
       \coordinate (O) at (0,0);
       \coordinate (i) at (1,0);
       \coordinate (j) at (0,1);
       
       \draw[-latex] (O) -- (i);
       \draw[-latex] (O) -- (j);
       
       \node[right] at (i) {$\underline{i}$};       
       \node[above] at (j) {$\underline{j}$};
       
       \node[anchor=north east] at (O) {$O$};
       \filldraw (O) circle(1pt);
       
   \end{tikzpicture}
\end{document}