This approach is not a simple environment but a standard minted environment nested in you own float environment. Not exactly the asked but:
☑ Each line in a src code block is numbered (optionally)
☑ The font used for a src code block is monospaced (and syntax highlited)
☑ A border is drawn around a code code block, much like \fbox does (with top caption inside using \stdcaption, for a botom caption outside the box use \caption*)
☑ Each code block "floats" to a position (concretely to top of a new page) so that it will fit all on one page.

\documentclass[a6paper]{article} \usepackage[margin=1cm, paperheight=5in,paperwidth=5in]{geometry} \pagestyle{empty} \usepackage{lipsum} \let\stdcaption\caption \setcounter{totalnumber}{1} \usepackage{minted} \usepackage{float} \floatstyle{boxed} \newfloat{fancycode}{t}{loa} \floatname{fancycode}{LaTeX code} \begin{document} \begin{fancycode} \stdcaption[Basic Structure]{The basic structure of a \LaTeX\ document.} \begin{minted}[linenos,bgcolor=orange!05]{latex} \documentclass{article} \begin{document} \end{document} \end{minted} \end{fancycode} \begin{fancycode} \stdcaption[Preamble]{The \LaTeX\ preamble to do a \texttt{fancycode}.} \begin{minted}[linenos,bgcolor=cyan!10]{latex} \usepackage{minted} \usepackage{float} \floatstyle{boxed} \newfloat{fancycode}{t}{loa} \floatname{fancycode}{LaTeX code} \end{minted} \end{fancycode} \lipsum[1-2] \listof{fancycode}{Code examples} \end{document}
srcblockcontain in terms of characters?verbatim-like content, perhaps (symbols like#,_,$,^, ...)?listingspackage? This should be straight-forward with it. Just read the manual.