\documentclass[10pt,a4paper]{article}

% Packages
\usepackage{fancyhdr}           % For header and footer
\usepackage{multicol}           % Allows multicols in tables
\usepackage{tabularx}           % Intelligent column widths
\usepackage{tabulary}           % Used in header and footer
\usepackage{hhline}             % Border under tables
\usepackage{graphicx}           % For images
\usepackage{xcolor}             % For hex colours
%\usepackage[utf8x]{inputenc}    % For unicode character support
\usepackage[T1]{fontenc}        % Without this we get weird character replacements
\usepackage{colortbl}           % For coloured tables
\usepackage{setspace}           % For line height
\usepackage{lastpage}           % Needed for total page number
\usepackage{seqsplit}           % Splits long words.
%\usepackage{opensans}          % Can't make this work so far. Shame. Would be lovely.
\usepackage[normalem]{ulem}     % For underlining links
% Most of the following are not required for the majority
% of cheat sheets but are needed for some symbol support.
\usepackage{amsmath}            % Symbols
\usepackage{MnSymbol}           % Symbols
\usepackage{wasysym}            % Symbols
%\usepackage[english,german,french,spanish,italian]{babel}              % Languages

% Document Info
\author{shorttcircuitt (shortt\_circuitt)}
\pdfinfo{
  /Title (os-interview-questions.pdf)
  /Creator (Cheatography)
  /Author (shorttcircuitt (shortt\_circuitt))
  /Subject (OS Interview Questions Cheat Sheet)
}

% Lengths and widths
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\addtolength{\voffset}{-2cm}
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\setlength{\headheight}{85pt} % If less, LaTeX automatically increases it
\renewcommand{\footrulewidth}{0pt} % Remove footer line
\renewcommand{\headrulewidth}{0pt} % Remove header line
\renewcommand{\seqinsert}{\ifmmode\allowbreak\else\-\fi} % Hyphens in seqsplit
% This two commands together give roughly
% the right line height in the tables
\renewcommand{\arraystretch}{1.3}
\onehalfspacing

% Commands
\newcommand{\SetRowColor}[1]{\noalign{\gdef\RowColorName{#1}}\rowcolor{\RowColorName}} % Shortcut for row colour
\newcommand{\mymulticolumn}[3]{\multicolumn{#1}{>{\columncolor{\RowColorName}}#2}{#3}} % For coloured multi-cols
\newcolumntype{x}[1]{>{\raggedright}p{#1}} % New column types for ragged-right paragraph columns
\newcommand{\tn}{\tabularnewline} % Required as custom column type in use

% Font and Colours
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\definecolor{LightBackground}{HTML}{F3F3F3}
\renewcommand{\familydefault}{\sfdefault}
\color{TextColor}

% Header and Footer
\pagestyle{fancy}
\fancyhead{} % Set header to blank
\fancyfoot{} % Set footer to blank
\fancyhead[L]{
\noindent
\begin{multicols}{3}
\begin{tabulary}{5.8cm}{C}
    \SetRowColor{DarkBackground}
    \vspace{-7pt}
    {\parbox{\dimexpr\textwidth-2\fboxsep\relax}{\noindent
        \hspace*{-6pt}\includegraphics[width=5.8cm]{/web/www.cheatography.com/public/images/cheatography_logo.pdf}}
    }
\end{tabulary}
\columnbreak
\begin{tabulary}{11cm}{L}
    \vspace{-2pt}\large{\bf{\textcolor{DarkBackground}{\textrm{OS Interview Questions Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{shorttcircuitt (shortt\_circuitt)} via \textcolor{DarkBackground}{\uline{cheatography.com/77499/cs/19026/}}}
\end{tabulary}
\end{multicols}}

\fancyfoot[L]{ \footnotesize
\noindent
\begin{multicols}{3}
\begin{tabulary}{5.8cm}{LL}
  \SetRowColor{FootBackground}
  \mymulticolumn{2}{p{5.377cm}}{\bf\textcolor{white}{Cheatographer}}  \\
  \vspace{-2pt}shorttcircuitt (shortt\_circuitt) \\
  \uline{cheatography.com/shortt-circuitt} \\
  \end{tabulary}
\vfill
\columnbreak
\begin{tabulary}{5.8cm}{L}
  \SetRowColor{FootBackground}
  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Not Yet Published.\\
   Updated 4th March, 2019.\\
   Page {\thepage} of \pageref{LastPage}.
\end{tabulary}
\vfill
\columnbreak
\begin{tabulary}{5.8cm}{L}
  \SetRowColor{FootBackground}
  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Sponsor}}  \\
  \SetRowColor{white}
  \vspace{-5pt}
  %\includegraphics[width=48px,height=48px]{dave.jpeg}
  Measure your website readability!\\
  www.readability-score.com
\end{tabulary}
\end{multicols}}




\begin{document}
\raggedright
\raggedcolumns

% Set font size to small. Switch to any value
% from this page to resize cheat sheet text:
% www.emerson.emory.edu/services/latex/latex_169.html
\footnotesize % Small font.

\begin{multicols*}{2}

\begin{tabularx}{8.4cm}{x{4.32 cm} x{3.68 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Endianess}}  \tn
% Row 0
\SetRowColor{LightBackground}
Big Endian & 01 23 45 67 \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
Little Endian & 67 45 23 01 \tn 
% Row Count 2 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{8.4cm}}{32 bit integer is 0x01234567}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{IPC}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{Semaphore} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{Mutex} \tn 
% Row Count 2 (+ 1)
% Row 2
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\mymulticolumn{1}{x{8.4cm}}{Message Passing} \tn 
% Row Count 3 (+ 1)
% Row 3
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{Shared Memory} \tn 
% Row Count 4 (+ 1)
% Row 4
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{Sockets} \tn 
% Row Count 5 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Interrupts}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{p{8.4cm}}{\vspace{1px}\centerline{\includegraphics[width=5.1cm]{/web/www.cheatography.com/public/uploads/shortt-circuitt_1551730117_Load_Interrupt_Handler.jpg}}} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Priority Inversion}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{In a scenario where a low priority task holds a shared resource (example semaphore) that is required by a high priority task. This causes the execution of the high priority task to be blocked until the low priority task has released the resource. This scenario is averted by the OS by increasing the priority of the low priority process until it completes the task and releases the resources% Row Count 8 (+ 8)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Stack and Heap}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{Stack Allocation} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}The allocation happens on contiguous blocks of memory. It happens in the function call stack. The size of memory to be allocated is known to compiler and whenever a function is called, its variables get memory allocated on the stack. And whenever the function call is over, the memory for the variables is deallocated. Handled by the compiler} \tn 
% Row Count 9 (+ 9)
% Row 1
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{Heap Allocation} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}The memory is allocated during execution of instructions written by programmers. It is called heap because it is a pile of memory space available to programmers to allocated and de-allocate. If a programmer does not handle this memory well, memory leak can happen in the program.} \tn 
% Row Count 17 (+ 8)
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Detect Endianess}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{void endian()  \newline \{ \newline   unsigned int i = 1; \newline   char {\emph{c = (char}})\&i; \newline   if (*c)     \newline      printf("Little endian"); \newline   else \newline      printf("Big endian"); \newline \}} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{RTOS}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{An RTOS will have a deterministic scheduler. \newline % Row Count 1 (+ 1)
For any given set of tasks your process will always execute every number of microseconds or milliseconds exactly, and the same number from schedule to schedule. \newline % Row Count 5 (+ 4)
OS services consume only known and expected amounts of time. \newline % Row Count 7 (+ 2)
In UNIX or Windows the scheduler are usually soft RT (as opposed to some hard real time RTOS). Soft realtime means that the scheduler tries to assure your process runs every X number of milliseconds, but may fail to do so on some occasions. \newline % Row Count 13 (+ 6)
Modern RTOSs simply make sure that a) no interrupt is ever lost, and b) no interrupt can be blocked by a lower priority process.% Row Count 16 (+ 3)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{2.08 cm} x{5.92 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Memory Management}}  \tn
% Row 0
\SetRowColor{LightBackground}
Paging & Blocks of memory that are stored in auxiliar memory and replaced in main memory when a program needs it. \tn 
% Row Count 4 (+ 4)
% Row 1
\SetRowColor{white}
Caching & Data is temporarily stored in high speed memory for faster access. \tn 
% Row Count 7 (+ 3)
% Row 2
\SetRowColor{LightBackground}
\seqsplit{Segmentation} & Segmentation is a memory management scheme. This is the technique used for memory protection. Any accesses outside premitted area would result in segmentation fault. \tn 
% Row Count 13 (+ 6)
% Row 3
\SetRowColor{white}
Virtual Memory & This technique enables noncontiguous memory to be accessed as if it were contiguous. Same as paging \tn 
% Row Count 17 (+ 4)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Stack Growth Direction}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{void checkStack() \newline \{ \newline    int i=2; \newline    int j=3; \newline  \newline    if(\&i \textgreater{} \&j) printf("downwards"); \newline    else printf("upwards"); \newline \}} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{Define 2 local variables one after other and compare their addresses.}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}


% That's all folks
\end{multicols*}

\end{document}