Question

Im working on a study guide for my Visual Basic final and im stuck up on this question.

Which of the following code segments will copy the values of a 5 element array named intOldValues into another 5 element array named intNewValues?
A)
intIndex = 1
Do While intIndex <=5
intNewValues = intOldValues
intIndex += 1
Loop
B)
intIndex = 0
Do While intIndex < 5
intNewValues = intOldValues
intIndex += 1
Loop
C)
For intIndex = 1 To 5
intNewValues = intOldValues
Next intIndex
D)
For intIndex = 0 To 4
intOldValues = intNewValues
Next intIndex

Any feedback would be appreciated

Answer 1

It's C or D, I just can't remember if VB is array base 0 or 1, let me check for you, hold on.

Answer 2

According to a quick search, VB has base 0 array indexes (unless overridden).
So the answer is D.
If you need an explanation, let me know.

Answer 3

I thought it was D too but I was unsure since it says intOldValues = intNewValues.
I figured that since we want to copy it to NewValues it would have to be intNewValues = intOldValues

Answer 4

Oh, I didn't even see that at first. You may be right, it could be C.
I remember VB being weird with arrays, and they start at 1 instead of 0.

I'm actually going to change my answer to C.

Do you have any more code that accompanies this question?

Answer 5

Yeah because it says intOldValues = intNewValues, that doesn't make any sense.

Answer 6

Okay, I'm looking on the MSDN, and yes VB arrays *DO* start at 1 when looping. So yes, the answer is in fact C

http://msdn.microsoft.com/en-us/library/5z06z1kb.aspx

Answer 7

Thanks Im glad we caught that trick.

Answer 8

Yes, sorry if I mislead you. I apologize for not seeing it at first.

Answer 9

Not a problem. Are you good with VB? I might have a few more questions.

Answer 10

I've programmed in VB for years, and I have never once been happy doing so :)

Answer 11

Haha, yes I am. Ask away, I'm just doing physics homework.

Answer 12

That'd be awesome. And just to clarify this isnt my homework. Its a study guide for my final so its not for a grade. I know some people get weird about giving answers to homework.

Answer 13

Yeah, if you need an explanation let me know. VB's not like other languages it's .... different (read: "frustrating"). So even if you just need clarification on just the answer, that's fine. :)

Answer 14

But feel free to ask away, I'll be up for another 20 or 30 minutes.

Answer 15

ok. Which of the following is the correct definition for a procedure that accepts a String array as an argument?

So the professor didnt give us options for some of the questions. I looked this up in the book and all I could find is to use a function but im not sure if thats what the answer would be

Answer 16

So, an array of strings?

Answer 17

Let me see....

Answer 18

MSDN Link: http://msdn.microsoft.com/en-us/library/vstudio/63y5ksfs(v=vs.100).aspx

Public Function PrintMyMessages(messages() As String) As Double
' ...
End Function

Answer 19

Oh ok so basically I need to just add the As String

Answer 20

You need to add the () after "messages"
That lets the function know it is an array

Answer 21

The As String is used to tell the function it is a string array

Answer 22

For example, if you had an array of doubles, "myDoubles() as Double"

Answer 23

Ok that makes sense and lines up with the book

Answer 24

Which of the following statements defines a two-dimensional Integer array named intTwoDArray with 6 rows and 4 columns? Dim intTwoDArray(5,3)

Is that right?

Answer 25

I believe it should be (6,4) (just like in any other language).
Let me verify.

Answer 26

I think 0 counts as a column

Answer 27

See ... yeah VB always has to be the weird one.
(5,3) declares the array indexes 0 through 5 as the col, and 0 through 3 for each row.

Answer 28

In any other language (like C), if you declare arr[4][3], it declares arr[0 through 3][0 through 2]

Answer 29

So you are correct.

Answer 30

Dim intTwoDArray(5,3)

Answer 31

MSDN: http://msdn.microsoft.com/en-us/library/02e7z943.aspx

Answer 32

Nice. Do have any idea what to make of this question?
Which of the following could be used to iterate through each element of a two-dimensional array.

Answer 33

"Which of the following" -> Does it give any multiple choice answers? I should know which one if you can provide them.

Answer 34

No it doesnt. Unfortunately.

Answer 35

I found options on google.

. A single Do While loop
A single Do Until loop
A single For Next loop
Nested loops For Next loops

Answer 36

Well what you normally do is this:

Say you have the array Dim intTwoDArray(5,3)

For the columns, we use the variable "i", and for the rows we use the variable "j"

Loop i from 0 to 5
Loop j from 0 to 3
'Do code
Next
Next

Answer 37

So is that D?

Answer 38

So the program would access the array like this:
Column 0, row 0
Column 0, row 1
Column 0, row 2
Column 0, row 3

Column 1, row 0
Column 1, row 1
Column 1, row 2
Column 1, row 3

Column 2, row 0
Column 2, row 1
Column 2, row 2
Column 2, row 3


...etc

Answer 39

Yes, D

Answer 40

Nice. I found some options for that As String question if you want to make sure i have the right answer.
. Private Sub ArrayParam(ByVal strStudents As String)
Public Sub ArrayParam(ByVal strStudents())
Sub ArrayParam(ByVal strStudents() As String)
Private Sub ArrayParam(ByRef strStudents As String)

Answer 41

Let me do a search. Normally in any language, arrays are automatically passed by reference (ByRef) regardless of type. But VB is .... special :)

brb.

Answer 42

Oh wait I don't even have to look it up. A and D don't have the parenthesis.

Answer 43

So C im guessing?

Answer 44

Yes it's C. I wanted to make sure.

MSDN (see "example"): http://msdn.microsoft.com/en-us/library/dz1z94ha.aspx

Answer 45

btw in case you need to know, ByVal means it makes a copy to the array. That means that anything you do to that array does not affect the original array.

On the other hand, if you pass ByRef, you are passing "By Reference", meaning you are referencing the original array. If you make any changes, they WILL affect the original array.

Answer 46

ByVal means it makes a copy of that array*

Answer 47

Oh ok so you can change values with by reference.

Answer 48

Right

Answer 49

So like, say for every value in the array I wanted to subtract 1. I would pass it by reference.

Answer 50

But say I REALLY don't want to affect any values in the array, I would pass by copy (ByVal)

Answer 51

Almost any language passes an array by reference, because it costs memory and time to make a copy of an array. But VB you must explicitly state which one you want every time.

Answer 52

Ya VB is killing me. Im taking C++ at the same time so you can only imagine the confusion

Answer 53

Would this one be B?
Which statement is the best solution for the following problem? Write a statement that initializes a two dimensional array of Integers named intGrades. The array will have 2 rows, with 93, 91, and 84 in the first row and 85, 89, and 91 in the second row.
Dim intGrades(2,3) As Integer = { {93, 91, 84}, {85, 89, 91} }
Dim intGrades(,) As Integer = { {93, 91, 84}, {85, 89, 91} }
Dim intGrades() As Integer = { 93, 92, 84,85, 89, 91}
Dim intGrades(1, 2) As Integer = { {93, 91, 84}, {85,89, 91} }

Answer 54

I don't even know what school would still offer VB as a language - it's nearly a dead language. C# and VB.NET are its replacements.

Answer 55

I took Java in highschool and I have to take VB C++ and C++ II as far as coding goes

Answer 56

D

intGrades(0,0) = 93
intGrades(0,1) = 91
intGrades(0,2) = 84

intGrades(1,0) = 85
intGrades(1,1) = 89
intGrades(1,2) = 91

Answer 57

ok. What would happen if i coded B?

Answer 58

I think it would give you a syntax error. I don't think that's legal to let the compiler assume the size of the array based on the right hand side. Although, I could be wrong.

Answer 59

They do it in the book but they declare MAXRows and MAXColumns

Answer 60

It seems like it's only either
Dim intGrades(1, 2) As Integer = { {93, 91, 84}, {85,89, 91} }
or
Dim intGrades = { {93, 91, 84}, {85,89, 91} }

Answer 61

They use (,) in the book?

Answer 62

For one of the example problems it goes.
Const intMAX_ROW = 5
Const intMAX_COL = 3

Dim decPrices( , ) = {{10D, 10D, 10D, 10D},
{20D, 20D, etc......

Answer 63

I just compiled all of these online, and they all work.

Answer 64

I know for certain it's not C

Answer 65

A is also incorrect, because (2,3) will give you 0-2 (3 columns) and 0-3 (4 rows)

Answer 66

Does the way the array is written define how many rows and columns it needs maybe?

Answer 67

It is (,) when you're specifying values.

MSDN: http://msdn.microsoft.com/en-us/library/y13tek7e.aspx

Answer 68

Always trust the MSDN, lol.

Answer 69

I have to head to bed, good luck on your final! (Please choose "best answer" if you thought I was helpful)

Answer 70

So is it B then? And i definetly will you were really helpful

Answer 71

It is B according to the MSDN... but I would write a quick program to check if both B and D work.

Answer 72

Ok Will do. Thanks for all your help

Answer 73

No problem at all :)
Anything to lessen the suffering of VB upon others, haha.

Answer 74

Haha right?! Night! Thanks again

Answer 75

It would seem that testing the options would be the best way to be 100% sure of the correct solution, and it would be fairly quick also