const reference parameter that allows read-only access

[austin004]

can somebody tell me the meaning of this "The function should use const reference parameter that allows read-only access to reference parameter without wasting space, speed."
Actually the question is;
Write a program that uses a structure named StudentData to store the following information about a student:
ID
name
major
year enrolled in school
GPA

The program should create two StudentData variables, store values in their members, and pass each one, in turn, to a function that displays the information about the student in a clearly formatted manner. The function should use const reference parameter that allows read-only access to reference parameter without wasting space, speed.

Although I have done the coding, i just want to know have i done it correct.

[mbozzi]

Here is the signature of a function accepting a parameter:
By value:
int foo(SomeType);
By reference:
int foo(SomeType&);
By constant reference:
int foo(SomeType const&);

You're expected to use the third technique. You can do the same thing for whatever SomeType is (except if SomeType is a reference type, in which case the references collapse--but don't worry about that) and for all the combinations of const and volatile applied to SomeType.

[austin004]

i had used the following code line can u confirm it.
void DisplayData(const StudentData &sd)

[mbozzi]

Yeah, it's correct.