If I want to connect my laptop, which has a VGA output, to a monitor, I plug a VGA cable into both ends. The output being my laptop, and the input the monitor

VGA output sockets are the same as VGA input sockets however, so what if I want to use my laptop as the monitor, with the video being outputted from somewhere else?

As I said, VGA's output is the same as input, so in theory, I have the hardware in my laptop to do this. But presumably I need some software.

So can I use the VGA port on a laptop as a video input?

(And also, can this be done with HDMI?)


Question: Table heading multicolumn problem
Answer: You can use \\ &amp;&amp; A&amp;B instead of \\ A&amp;B.  The first two &amp;&amp; are to skip over the first two columns.



Notes:


As per Bernard'scmment,  the multirow package was used to vertically center the first two headers across the two rows. 
As per @AlanMunn's comment, \cline{3-4} can be used to draw lines across specified columns.




However, I would strongly recommend you have a look at the booktabs package for tables:



Code:

\documentclass{article}
\usepackage{multirow}

\begin{document}
\begin{tabular}{|c|l|c|c|}
    \hline
    \multirow{2}{*}{\bfseries First} &amp; 
    \multirow{2}{*}{\bfseries Characteristics} &amp; 
    \multicolumn{2}{|c|}{\bfseries Implemented in}\\ \cline{3-4}
    &amp;&amp; A&amp;B \\ \hline
    %------
    &amp; b &amp; c &amp; d \\
    1 &amp; 2 &amp; 3 &amp; 4\\
\end{tabular}
\end{document}


Code: booktabs

\documentclass{article}
\usepackage{booktabs}
\usepackage{multirow}

\begin{document}
\begin{tabular}{c l c c}
    \toprule
    \multirow{2}{*}{\bfseries First} &amp; 
    \multirow{2}{*}{\bfseries Characteristics} &amp; 
    \multicolumn{2}{c}{\bfseries Implemented in}\\ \cmidrule(lr){3-4}
    &amp;&amp; A&amp;B \\ \cmidrule(lr){1-4}
    %------
    &amp; b &amp; c &amp; d \\
    1 &amp; 2 &amp; 3 &amp; 4\\
    \bottomrule
\end{tabular}
\end{document}