two small queries

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05-27-2011
jackson6612

two small queries

The quoted text is from a book.

Quote:

The most important reason to use functions is to aid in the conceptual organization of a program. Dividing a program into functions is, as we discussed in Chapter 1, “The Big Picture,” one of the major principles of structured programming. (However, object-oriented programming provides additional, more powerful ways to organize programs.)

Another reason to use functions (and the reason they were invented, long ago) is to reduce program size. Any sequence of instructions that appears in a program more than once is a candidate for being made into a function. The function’s code is stored in only one place in memory, even though the function is executed many times in the course of the program. Figure 5.1 shows how a function is invoked from different sections of a program.

I don't think the most important reason to use functions is to aid in the conceptual organization of a program rather the most important reason is to reduce the size of the program and save memory. What do you say? Please let me know.

Quote:

24. A default argument has a value that
a. may be supplied by the calling program.
b. may be supplied by the function.
c. must have a constant value.
d. must have a variable value.

According to the book the answers are "a" and "b". I don't understand how "a" could be the answer. Please help me. Thanks.
05-27-2011
laserlight

Quote:

Originally Posted by jackson6612

I don't think the most important reason to use functions is to aid in the conceptual organization of a program rather the most important reason is to reduce the size of the program and save memory. What do you say?

Well...

Quote:

Originally Posted by Abelson and Sussman

Programs must be written for people to read, and only incidentally for machines to execute.

Quote:

Originally Posted by jackson6612

According to the book the answers are "a" and "b". I don't understand how "a" could be the answer.

When the caller chooses not to use the default value.
05-27-2011
grumpy

Quote:

Originally Posted by jackson6612

I don't think the most important reason to use functions is to aid in the conceptual organization of a program rather the most important reason is to reduce the size of the program and save memory. What do you say? Please let me know.

I agree with your book and strongly disagree with you in this case.

For anything except a small program, human effort is the dominant practical driver (exceeding 80% in a lot of studies, and exceeding 90% in quite a few studies) of cost and time to get a program working correctly and then maintaining it. Anything that reduces human time and effort is therefore critical to reducing development cost, effort, and ensuring program correctness. Functions make a program easier to think about, so are an important tool for reducing development cost (albeit not the only one).

Note in the above, my working definition of a "small program" probably covers programs that you might consider to be on the large side. I personally define a small program as one for which the first five years of its development life cycle (design, development, initial maintenance) takes less than ten man years of effort.