DOC: Add guideline on using a backslash as line continuation character

Follow-up to ITK pull request
InsightSoftwareConsortium/ITK#3713 commit
InsightSoftwareConsortium/ITK@69151c3
"STYLE: Remove backslash + indent from literals, to avoid unwanted spaces"

Author: N-Dekker

SoftwareGuide/Latex/Appendices/CodingStyleGuide.tex

@@ -62,6 +62,8 @@ \section{Overview}%
 argument lists.
 \item \textbf{Ternary Operator}: accepted standards for using the ternary
 operator.
+\item \textbf{Backslashes}: guideline on using a backslash as line continuation
+character.
 \item \textbf{Using Standard Macros} (itkMacro.h): use of standard macros in
 header files.
 \item \textbf{Exception Handling}: how to add exception handling to the system.
@@ -3258,6 +3260,43 @@ \section{Ternary Operator}%
 And hence, the ternary operator is accepted in such cases.
 
 
+\section{Backslashes}%
+\label{sec:Backslashes}
+
+The use of a backslash as line continuation character sometimes
+hampers code readability. A backslash at the end of a line that has C++ \code{//}
+comment may be quite confusing. For example, it may be overlooked easily that
+the following code has commented out the \code{Sleep()} function call:
+
+\small
+\begin{minted}[baselinestretch=1,fontsize=\footnotesize,linenos=false,bgcolor=ltgray]{cpp}
+  // Will we go to sleep or not? \
+  Sleep();
+\end{minted}
+\normalsize
+
+The use of backslashes in a multiline string literal is
+troublesome. For example, the following \code{badDescription} has all the space
+characters of the indentation between \enquote{developers with } and \enquote{an extensive suite}
+embedded inside the string, which may not be intended. The definition of
+\code{goodDescription} shows how to define such a lengthy string properly (as
+the compiler concatenates adjacent string literals automatically).
+
+\small
+\begin{minted}[baselinestretch=1,fontsize=\footnotesize,linenos=false,bgcolor=ltgray]{cpp}
+    const char badDescription[] = "ITK is an open-source, cross-platform library that provides developers with \
+                                   an extensive suite of software tools for image analysis.";
+//|||||||||||||||||||||||||||||||||<- 36 extra spaces included between "with" and "an" in sentence above
+
+    const char goodDescription[] = "ITK is an open-source, cross-platform library that provides developers with "
+                                   "an extensive suite of software tools for image analysis.";
+\end{minted}
+\normalsize
+
+The use of a backslash as line continuation character is discouraged in standard C++ code blocks.
+Backslashes are allowed when defining lengthy preprocessor macros to allow for
+improved readability when they span multiple lines.
+
 \section{Using Standard Macros}%
 \label{sec:UsingStandardMacros}