Once Upon a Time, a young engineer went for a walk in the forest.
He came upon an old man, sitting on a tree stump, staring into space.
"Hello," he said, "What are you doing here?"
"Ah," said the old man, "I used to be a draftsman, but then I went mad, so they sent me here."
"Oh? Why did you go mad?" said the young engineer.
"It does not matter now, " the old draftsman replied, "but it was something about drawings that had to be changed,
and then they wanted me to draw a diagram of the Hazardous Areas in the plant, anyway, I see you are an engineer."
"How did you pick that?"
"Well, it's easy. You have in your hand a bunch of drawings that are printed out with grey lines instead of black."
"Oh that....Well I just get into Autocad and hit the Print button and that's what I get."
A glimmer of hope entered the old draftsman's eye and he said:
"You know, you don't have to do that. It is very simple not to, can I explain how to do it?"
"Noooooo!" wailed the young engineer, "I'm an engineer, I don't have to know that stuff!"
"Please!" entreated the old draftsman, falling to his knees and tugging on the young engineer's sleeve,"you can do it!
After all, you must be reasonably clever just to do those Engineer's Exams?"
"Well...I suppose so." he answered.
"OK," said the old draftsman "it goes like this: Once upon a time in a land far away and long ago,two elves were designing Autocad."
One turned to the other and said: "How are we going to get thick and thin lines to come out?"
To which the other replied "I know, let's make it one colour for thin lines and another for thick lines."
Then the other said: "How can we make the computer remember which colours are related to which fat or thin lines?"
"That's easy," replied the other, "we can store the values in a separate file,let's call the file extension .ctb,
which stands for colour table....hmm dunno what the b stands for but we have to have 3 letters so there you go."
The old draftsman, sighed, and said:
"Well that's all there is to it: Just hit the print button and in the top right hand corner of the dialog box
there is a selection of ctb files to choose from. I'd suggest you choose the one your draftsman seems to use-
you can spot it right away usually,because it is right at the bottom of the list, called something like 'Freds.ctb'."
The young engineer lived happily ever after.