Programming Concepts

Question 1

Give code to make a dynamic array in C++. Then the code to delete it.

Answer 1

int size;
Double *arrayName;
cin >> size;
arrayName = new double[size];
delete [ ] arrayName;

Question 2

Name a Unix editor. Two if you can.

Answer 2

Vi. Another acceptable answer is PICO.

Question 3

What is a dangling pointer in C++? Show code to illustrate.

Answer 3

Where ptr1 points to ptr2. Then ptr2 gets deleted. 
*ptr1 = new Node;
*ptr2 = new Node;
ptr1 = ptr2;
delete ptr2;

Question 4

What is a memory leak? Give code to illustrate.

Answer 4

It is where dynamic data becomes inaccessible due to someone not deleting something properly. 
*ptr1 = new Node;
*ptr2 = new Node;
ptr1 = ptr2;
delete ptr2; // ptr1 is now inaccessible

Question 5

What is Putty or SSH?

Answer 5

It is a program used to connect to a remote Unix system.

Question 6

In recursion, what are the two minimal things necessary?

Answer 6

Base Case: A case where the answer is known.

General Case: The recursive algorithm that changes/looks at something then calls itself.

Question 7

What’s the difference between passing by reference and passing by value?

Answer 7

Pass by Value: This COPIES the variable being passed into the function. The variable itself is not altered.

Pass by Reference: This passes the actual variable itself into the function and therefore will be altered elsewhere.

Question 8

What is a copy constructor and when are they typically used?

Answer 8

A copy constructor is called whenever a deep copy needs to be made (passed by reference). This is typically used in arrays, vectors and dynamic data.

Question 9

What is a deep copy?

Answer 9

It makes a Copy of the entire variable. All the data members, pointers, and arrays.

Question 10

Using the class “Person” give the code for overloading the + operator.

Answer 10

const Person operator+(const Person& obj)

Question 11

What is polymorphism?

Answer 11

The reclassification of code based on the the circumstances. The code will behave differently depending on different contexts.

Question 12

Give a few examples of polymorphism.

Answer 12

Inheritance

Operator Overloading

Virtual Functions

Question 13

What is a virtual function?

Answer 13

A virtual function is a generalization of a function. Virtual functions are usually overridden, and pure virtual functions MUST be overridden.

Question 14

What is the advantage of using exceptions in your code?

Answer 14

If you want to catch a problem in your code you just throw an exception. This allows you to handle the exception somewhere other than where it occurred.

Question 15

Make the template and header code for a function “Print” that passes a template value T named val.

Answer 15

template
void Print( T val ){ }