Need to Know

In computer programming letters or words are used as symbols standing for information. For example: the symbol “name” can stand for “Mary Jones,” “Jack Smith,” or “Thomas Mann.” The symbol is “name;” the data is “Mary Jones,” “Jack Smith,” or “Thomas Mann.” Don’t worry yet about how we get there: just think of “name” as a container that can hold any one of the given and family names of our individuals. If I arrange my people in a list then I can refer to them as name(1), name(2), name(3).

Alternatively, the symbol “x” can stand for any number. If I want to count from 1 to 10, I can increment (raise by step) the value of a symbol that stands for a number. A common way of notating that in many languages is: x = x + 1. In other words, you take the number that is represented by “x,” add 1 to it, then store the result back in the symbol “x.”

Putting these two ideas together we can tell the computer to fetch all the names in our list by using the two symbols “name” and “x” as in “name(x)”. We don’t know—or even care—the content of any of our containers. We just know that if we tell the computer to print whatever is in container “name” in row number “x” it will print out one of our names—depending on what the value of x is.

Now you know everything there is to know about computers. Almost.

In the two examples above, our symbols represented actual data, whether it be names or numbers. If you tell the computer “print name(2)” it will not print out literally “name(2)” but will, instead, print out the data represented by those symbols. In other words, it will print “Jack Smith.” A computer can do thousands or even millions of these kinds of data retrievals in a second (though it will take much longer to actually print the list). If you had a list of the name of every person in Canada you could have a computer fetch any name, sort the list by any key you wished, find all the people named “Smith,”—or whatever you can think of doing with such a list—in the blink of an eye.

But, what if you wanted to manipulate the data in another section of a program? For example, you might want to reverse given and family names. So, you would write a routine that would parse (split into parts) the contents of name(x), then put the parts back together in reverse order. Such commands might look something like this:

first, last = parse(name(x),” “);
name(x) = last & first;

(We are assuming that the computer language has some sort of “parse” command built in that will split a string of characters using whatever delimiter (in this case a blank space) you tell it to use. And we are also assuming the language uses the symbol “&” to concatenate two individual pieces data.)

Did you notice what we did? We changed the data stored in our symbols “name,” row “x”. I mentioned that our procedure that did the name reversal was “in another section of a program.” We do this so that we have to write the commands to reverse the names only once. If we call our name swapping section “switch,” for example, then, in the main part of our program all we need to do is tell the computer to go to section “switch” and execute its operations on the data we have selected. And, because we are fetching our data by using a symbol called “name” and the information in “name” is in rows called “x,” we can write a compact little program. Sort of like this:

x = 0;
while (x <= 10)
x = x + 1;
print name(x);
switch (name(x));
print name(x);
end while;

The section we have called “switch” would be along the lines of the two lines of code that we wrote above. (Here we are assuming that the characters “<=” would mean “less than or equal to” in the language we are using.)

When we passed our data to the section called “switch” we were telling it to use the data that is represented by the symbols “name” and “x”. The “switch” routine then did its thing and changed the data stored at that location. So when x equals one, our program would print:

Mary Jones
Jones Mary

As the value of x is incremented it will do the same thing with the other names in our list.

But now, what if another program wanted to use our little “switch” procedure and, instead of using the symbols “name” and “x” to stand for data, it uses the symbols “person” and “number”? It will make no difference to our “switch” routine. It would still split the data into two parts then reverse them. The data represented by the symbols person(number) in the new program would be exactly the same as the data represented by name(x)in our procedure.

So, do you get it?

When I worked at Corrections Canada I wrote programs that fetched the data about their clients. I did not care what the actual data was—nor did I want to know it—all I had to worry about was the format that the data was stored in so that I could extract whatever part of the entire information field I needed. For example, if my manager told me that a senior official wanted to know how many persons are in federal prisons who were convicted of non-violent crimes and have less than six months left in their sentence, I could write program that would get the data based on that information (non-violent; less than 6 months) and count them. Bingo! Zip! As fast as that I would get an answer that I could email to my manager (who would pass it to his supervisor, who would pass it to his department head, who would send it to the department head where the senior official worked, who would send it …on and on until the information reached its destination.) My job would be in serious jeopardy if I had emailed the answer to the senior official directly.

In any case, the distance I had from the data about our government’s long-term guests was called “Need to Know.” The only thing I needed to know about was the format of the information about the prisoners. I didn’t need to know their names or any of the myriad of personal details that the government stores about its guests. No matter what projects I worked on, whether at a military research lab, a national library, or the prime minister’s office, the format of the data was all I ever needed to know. I really didn’t want to know more than that.