[Tex/LaTex] Undefined Control Sequence error message

Question

I have just started using Latex, Here is the code I have used (Texstudio editor):

\documentclass{article}
\usepackage{parskip}
\usepackage[margin=3.5cm]{geometry}
\usepackage{makeidx}
\usepackage{paralist}
\usepackage{amsmath,amssymb}
\usepackage{mdwtab}
\usepackage{graphicx,subfigure}
\DeclareMathSymbol{,}{\mathord}{letters}{''3B}
\newcommand{\np}{\newpage}
\begin{document}
\title{DSC4830\\[3mm]
    Research Project\\[5mm]
    Department of Decision Sciences\\[1cm]
    Assignment 1\\[5mm]
    Typing in \Latex\\[1cm]
}
\author{\textbf{\Large Lashner Ciorovich}\\[3mm]
    /textbf{\Large 07364598}
}
\maketitle
\thispagestyle{empty}
\np
\tableofcontents
\np
\end{document}

I keep getting the following logs:

Missing number, treated as zero. \DeclareMathSymbol{,}{\mathord}{letters}{''3B}
Missing \begin{document}. \DeclareMathSymbol{,}{\mathord}{letters}{''3B}
Undefined control sequence. \maketitle

Please can someone tell me what is wrong with my code?

Thank you.

Answer 1

The problem is that you typed '' instead of " in the math symbol definition.

By the way there were other errors too, mainly:

1. The LaTeX logo is printed using \LaTeX, not \Latex

2. you had a /textbf instead of \textbf

3. finally, are you really sure about your substituting the comma and make it an ord math atom? EDIT should you want to use the comma as a decimal separator (as @GustavoMezzetti suggests), try and use the siunitx package, specifically loading it like \usepackage[output-decimal-marker={,}]{siunitx}. I recommend you skim through its documentation (you could obtain it also typing texdoc siunitx in your terminal window).

Anyway, here is my cleared up code

\documentclass{article}
\usepackage{parskip}
\usepackage[margin=3.5cm]{geometry}
\usepackage{makeidx}
\usepackage{paralist}
\usepackage{amsmath,amssymb}
\usepackage{mdwtab}
\usepackage{graphicx,subfigure}
\DeclareMathSymbol{,}{\mathord}{letters}{"3B}
\newcommand{\np}{\newpage}
\begin{document}
\title{DSC4830\\[3mm]
    Research Project\\[5mm]
    Department of Decision Sciences\\[1cm]
    Assignment 1\\[5mm]
    Typing in \LaTeX\\[1cm]
}
\author{\textbf{\Large Lashner Ciorovich}\\[3mm]
    \textbf{\Large 07364598}
}
\maketitle
\thispagestyle{empty}
\np
\tableofcontents
\np
\end{document}

which outputs