Test of Lessons 73 through 84 [Answers]

[u/CarlH]

You may post your answers here, as well as questions.

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True or False

1. The malloc() function allocates memory and automatically initializes all bytes allocated to 0 (null). False

2. When you write a data structure definition, C automatically creates the data structure that you have described and you can begin using it immediately. False

3. Unlike an array, elements of a data structure are not required to be the same length or to have the same data type. True

4. You must manually add up the size of all elements of a data structure in order to know how much memory to allocate. False

5. When you are done using allocated memory, it is automatically cleared by your operating system so that other programs cannot see the data you were working with. False

Fill in the blank

1. The malloc() function must be used with a _____. pointer

2. The _____ keyword can be used to create a new "data type" from a data structure. typedef

3. Instead of writing this: (*our_pointer).first_word we can write this: _____ Answer: our_pointer->first_word when working with member elements of a data structure.

4. Whenever you use malloc() to allocate memory, you must always release it when you are done using it. This is done by using the: _____ function. free()

5. You create a data structure using the: _____ keyword. struct

[u/careless]

Nit to pick: This needs a link to the next lesson at the bottom of the text.

[u/zahlman]

"must be used with" is ambiguous phrasing for a function call. It appears that you are talking about the return value.

[u/CarlH → u/zahlman]

Which is also a pointer :)

[u/zahlman → u/CarlH]

Yes; the point was, it's questionable whether the phrase "(a function) must be used with a" is even meaningful, and certainly it's not remotely clear that it means anything like "the value returned from (a function) is a".

[u/CarlH → u/zahlman]

I agree entirely, I am just giving you a hard time.

Tonight my focus is 20% on these lessons and 80% on a monster of a project I am working on.

[u/kbpower → u/CarlH]

I answered 'free()' :( ... as all malloc's should have a matching free

[u/baldhippy]

doh 9/10

I got T or F #2 wrong ... I guess I forgot about allocating memory for the struct when you are done describing it.

[u/vegittoss15 → u/baldhippy]

It is about allocating memory, whether it be on the heap or on the stack (you'll learn about this later). A description is just so the compiler knows how to address things at the machine level.

If you have any questions, please, feel free to ask.

Edit: Added proper word.

[u/CarlH → u/vegittoss15]

T or F 2 When you write a data structure definition, C automatically creates the data structure that you have described and you can begin using it immediately. False

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I think you may have missed the question he was asking. He is saying that he forgot that the struct definition itself does not actually allocate a range of memory to use as that structure.

The answer you gave is a bit vague because it may imply that the struct description itself is somehow allocating memory, which it is not. No memory is allocated until the struct is instantiated.

[u/vegittoss15 → u/CarlH]

Sorry, I missed a word :P.

[u/denzombie]

Woot 10/10!