algorithmicx

You can define your own keywords when using the algorithmicx package. Section 3.1.10 Changing command names of the package documentation discusses the use of algnewcommand/algrenewcommand that you can use to create a new command/change existing formatting. The following two images are taken directly from the package documentation:

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algorithm2e

You can also define your own keywords using the algorithm2e package. Section 10 To define your own language keywords of the package documentation discusses this in detail. Specifically, you use commands like

• SetKwInput and SetKwOutput for algorithm input / output definition
• SetKw for keyword definitions
• SetKwBlock for block definitions
• SetKwFunction for function / procedure definitions
• SetKwComment for comment definitions
• SetKwIf for if-statement definitions
• SetKwSwitch for multiple condition selection definitions
• SetKwFor for for loop definitions
• SetKwRepeat for repeat / while definitions

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listings

Then there's the listings package that allows just as much modification. Keyword definitions are specified via styles and/or languages. Read the highly detailed package documentation for more information on this.

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tabbing

The above use some rich programming directives from package that probably require a lot of reading. In the special case where you "just want to write a couple of lines of code and format stuff your own way", you could use the tabbing environment. This is either provided by LaTeX (as default) or by the tabbing package. The tabbing package documentation gives some motivation for using it, but that's up to you.

A typical tabbing environment would resemble

begin{tabbing}
  <space> = <space> = <space> = <space> = kill
  no indent > > more text 
  > one indent > 
  ....
  ....
end{tabbing}

where the tab stops a indicated by = and jumped to by using >. It is best to put empty spacing in the first row (via hspace{<space>}, quad, qquad or phantom{<stuff>}), since a first-line kill is provided (as opposed to [-baselineskip]) to prevent the first line from being typeset. This ensures that the actual tabbing typesetting starts in the first row.

The advantage here is that you can format your code the way you want, without any special package "interrupting" your style or other preferences. Given your example, here is what I would do (without using multicol):

documentclass{article}
usepackage{calc}% For length calculations
begin{document}

newlength{mylen}%
setlength{mylen}{linewidth-2fboxsep-2fboxrule}%

fbox{begin{minipage}{mylen}
  begin{tabbing}
    quad = quad = quad = hspace{5cm} = kill
    textbf{program} test > > > > texttt{some text here} 
    textbf{var} 
    > $i$ : textbf{integer}; > > > texttt{...} 
    > $b$ : textbf{boolean}; 
    textbf{begin} 
    > $i:=1$; > > > texttt{...} 
    > $b:=texttt{true}$; 
    > textbf{while} $i<15$ textbf{do} 
    > > $i:=i+1$; 
    > > $b:=textbf{not} b$; > > texttt{some text here} 
    > textbf{od} 
    textbf{end}
  end{tabbing}
end{minipage}}

end{document}

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verbatim

The verbatim environment is a paragraph-making environment that gets LaTeX to print exactly what you type in. It turns LaTeX into a typewriter with carriage returns and blanks having the same effect that they would on a typewriter. The output looks exactly as it looks in the input file. Typical typesetting in verbatim would resemble

begin{verbatim}
  <stuff> 
end{verbatim}

or

begin{verbatim*}
  <stuff>
end{verbatim*}

where the difference between verbatim and verbatim* is that the latter prints spaces as "visual" spaces, i.e., a short, squat "u". Inline verbatim is also possible using

verb char literal_text char

or

verb*char literal_text char

with a similar meaning as before for the unstarred and starred versions. There may be no space between verb or verb* and char (space is shown here only for clarity). Here char denotes the verb delimiters and should match at the start and end. char can be anything except a space (or a * for the verb form).