\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{{[}deleted{]}}
\pdfinfo{
  /Title (data-representation-aqa-computer-science.pdf)
  /Creator (Cheatography)
  /Author ({[}deleted{]})
  /Subject (Data Representation - AQA Computer Science Cheat Sheet)
}

% Lengths and widths
\addtolength{\textwidth}{6cm}
\addtolength{\textheight}{-1cm}
\addtolength{\hoffset}{-3cm}
\addtolength{\voffset}{-2cm}
\setlength{\tabcolsep}{0.2cm} % Space between columns
\setlength{\headsep}{-12pt} % Reduce space between header and content
\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
\definecolor{HeadBackground}{HTML}{333333}
\definecolor{FootBackground}{HTML}{666666}
\definecolor{TextColor}{HTML}{333333}
\definecolor{DarkBackground}{HTML}{5200A3}
\definecolor{LightBackground}{HTML}{F4EFF9}
\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{Data Representation - AQA Computer Science Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{{[}deleted{]}} via \textcolor{DarkBackground}{\uline{cheatography.com/56036/cs/15729/}}}
\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}{[}deleted{]} \\
  \uline{cheatography.com/deleted-56036} \\
  \end{tabulary}
\vfill
\columnbreak
\begin{tabulary}{5.8cm}{L}
  \SetRowColor{FootBackground}
  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Published 14th May, 2018.\\
   Updated 14th May, 2018.\\
   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{3.04 cm} x{4.96 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Number Bases}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Denary}} or {\bf{Decimal}} & Base 10. \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
{\bf{Binary}} & Base 2. Used by computers to represent all data and instructions. Uses 1s and 0s to powers of 2 to represent whole numbers. \tn 
% Row Count 8 (+ 6)
% Row 2
\SetRowColor{LightBackground}
{\bf{Hexadecimal}} & Base 16. Used in computing because more values can be represented by fewer characters. This makes it easier for humans to read and understand. \tn 
% Row Count 14 (+ 6)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{3.36 cm} x{4.64 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Converting Between Number Bases}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Denary}} to {\bf{Binary}} & Divide by 2, then read the remainders backwards. \tn 
% Row Count 3 (+ 3)
% Row 1
\SetRowColor{white}
{\bf{Binary}} to {\bf{Denary}} & Multiply the binary numbers (i.e. every single digit) by the relevant place value, then add all of these together. \tn 
% Row Count 8 (+ 5)
% Row 2
\SetRowColor{LightBackground}
{\bf{Denary}} to {\bf{Hexadecimal}} & Divide by 16, then read the divisors and remainder backwards. Then convert digits to hex digits. \tn 
% Row Count 13 (+ 5)
% Row 3
\SetRowColor{white}
{\bf{Hexadecimal}} to {\bf{Denary}} & 1. Separate the hex digits \{\{nl\}\} 2. Convert each digit to binary \{\{nl\}\} 3. Concatenate, then convert to denary \tn 
% Row Count 18 (+ 5)
% Row 4
\SetRowColor{LightBackground}
{\bf{Binary}} to {\bf{Hexadecimal}} & Convert to denary, then hex. \tn 
% Row Count 20 (+ 2)
% Row 5
\SetRowColor{white}
{\bf{Hexadecimal}} to {\bf{Binary}} & Convert to denary, then binary. \tn 
% Row Count 22 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{8.4cm}}{\bf\textcolor{white}{Binary Addition}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{Image could not be loaded.} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{Image: \seqsplit{http://chortle.ccsu.edu/assemblytutorial/Chapter-08/ass08\_3.html}}  \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}{Binary Shifts}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{p{8.4cm}}{\vspace{1px}\centerline{\includegraphics[width=5.1cm]{/web/www.cheatography.com/public/uploads/danielles_1526261082_bin-shift.png}}} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{{\bf{Binary shifts}} can be used for multiplication and division by powers of two. \newline  \newline Image: \seqsplit{http://wiki.schoolcoders.com/gcse/data-representation/numbers/binary-shift/}}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{1.9 cm} p{0.76 cm} x{4.94 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{3}{x{8.4cm}}{\bf\textcolor{white}{Units of Information}}  \tn
% Row 0
\SetRowColor{LightBackground}
Bit & b & A single binary digit. \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
Byte & B & 8 bits. \tn 
% Row Count 2 (+ 1)
% Row 2
\SetRowColor{LightBackground}
Kilobyte & kB & 1,000 bytes \tn 
% Row Count 3 (+ 1)
% Row 3
\SetRowColor{white}
Megabyte & MB & 1,000 kilobytes. \tn 
% Row Count 4 (+ 1)
% Row 4
\SetRowColor{LightBackground}
Gigabyte & GB & 1,000 Megabytes. \tn 
% Row Count 5 (+ 1)
% Row 5
\SetRowColor{white}
Terabyte & TB & 1,000 Gigabytes. \tn 
% Row Count 6 (+ 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}{ASCII vs Unicode}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{8.4cm}}{What is {\bf{ASCII}}?} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}A character set that uses 7 bits, so can represent up to 128 characters; this means that only Latin letters can be used (i.e. characters/letters from other languages can't be represented). However, it takes up less space that Unicode.} \tn 
% Row Count 6 (+ 6)
% Row 1
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{What is {\bf{Unicode}}?} \tn 
\mymulticolumn{1}{x{8.4cm}}{\hspace*{6 px}\rule{2px}{6px}\hspace*{6 px}Unicode is also a character set, but it can represent many, many values, including non-Latin-based languages.} \tn 
% Row Count 10 (+ 4)
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{2.64 cm} x{5.36 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Representing Images}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Pixel}} & A single point in a graphical issues. Short for 'picture element'. \tn 
% Row Count 3 (+ 3)
% Row 1
\SetRowColor{white}
{\bf{Bitmap}} & A grid of pixels, with each pixel represented by a binary number. \tn 
% Row Count 6 (+ 3)
% Row 2
\SetRowColor{LightBackground}
{\bf{Colour depth}} & Number of colours that can (not necessarily are) be represented in an image, and the corresponding number of bits needed to represent each pixel (e.g. 2 bits for 4 colours). The greater the colour depth, the bigger the file size. \tn 
% Row Count 15 (+ 9)
% Row 3
\SetRowColor{white}
{\bf{Resolution depth}} & How much detail there is in an image. The more pixels per inch, the higher the resolution. The higher the resolution, the bigger the file size. \tn 
% Row Count 21 (+ 6)
% Row 4
\SetRowColor{LightBackground}
{\bf{Metadata}} & Gives the software the information needed to display the image properly (size, resolution depth, colour depth). \tn 
% Row Count 26 (+ 5)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{8.4cm}}{Bitmap file size = width x height x colour depth (in bits)}  \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}{Data Compression}}  \tn
\SetRowColor{white}
\mymulticolumn{1}{x{8.4cm}}{{\bf{Data compression}} is used to reduce file size, which means that they take up less storage space. {\bf{Lossy}} compression is where some data is removed - this means that an image would lose some detail. {\bf{Lossless}} compression preserves all of the information. \newline % Row Count 6 (+ 6)
\{\{nl\}\}{\bf{Run length encoding}} (RLE) uses data frequency pairs to reduce the amount of data stored. It does so by stating the character and then the length of the run. Example: \newline % Row Count 10 (+ 4)
1001 1111 0101 can be shown as 1 1  2 0  5 1  1 0  1 1  1 0  1 1 \newline % Row Count 12 (+ 2)
\{\{nl\}\}{\bf{Huffman coding}} is more efficient than RLE. It is also lossless. It finds the frequency of each data item to create a Huffman tree, which assigns the most frequent items the shortest code. When you move down a branch to the left, a 0 is assigned. When you move to the right, a 1 is assigned. \newline % Row Count 19 (+ 7)
total bits needed = number of bits needed per character x number of characters% Row Count 21 (+ 2)
} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{2.96 cm} x{5.04 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Representing Sound}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Sample}} & A measure of amplitude at a given point. Used to convert an analogue wave into a digital format. \tn 
% Row Count 4 (+ 4)
% Row 1
\SetRowColor{white}
{\bf{Sampling rate}} & The number of samples taken in a second. Measured in Hertz. \tn 
% Row Count 7 (+ 3)
% Row 2
\SetRowColor{LightBackground}
{\bf{Sampling resolution}} & The number of bits per sample. \tn 
% Row Count 9 (+ 2)
% Row 3
\SetRowColor{white}
{\bf{Bit rate}} & The number of bits used per second of the audio. Usually measured in kilobits per second (kbps). \tn 
% Row Count 13 (+ 4)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{8.4cm}}{File size (bits) = sampling rate x resolution x lenght of recording (seconds)}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}


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

\end{document}