Core Programming

Question 1

int

Answer 1

4 bytes / 32 bits
can store whole numbers only
from -2,147,483,648 to 2,147,483,647.

It is the preferred data type when we create variables with a numeric value.

Question 2

long

Answer 2

8 bytes / 64 bits

can only store whole numbers

from
-9(Quintillion),223(Quadrillion),372(Trillion),036(Billion),854,775,808 to 9223372036854775807.
This is used when int is not large enough to store the value. Note that you should end the value with an “L”:

Question 3

float

Answer 3

signed 4 bytes / 32 bits
Stores fractional numbers.
Sufficient for storing 6 to 7 decimal digits

The float data type can store fractional numbers from 3.4e−038 to 3.4e+038. Note that you should end the value with an “F”:

Question 4

double

Answer 4

signed 8 bytes / 64 bits
Stores fractional numbers.
Sufficient for storing 15 decimal digits

Question 5

bool

Answer 5

1 bit Stores true or false values

Question 6

char

Answer 6

2 bytes / 16 bits

Stores a single character/letter, surrounded by single quotes

Question 7

string

Answer 7

2 bytes / 16 bits per character Stores a sequence of characters, surrounded by double quotes

Question 8

decimal

Answer 8

signed 16 bytes / 128 bits
Stores a fractional number
up to 28-29 digits
Should end in M - decimal price = 1.50M;

Question 9

To minimize the amount of storage used on the hard drive by an application that generates many small files, you should make the ______ as small as possible.

a - partition
b - file allocation table
c - block size
d - folder and file names

Answer 9

block size

Question 10

byte

Answer 10

unsigned 8 BIT / 1 byte

0 to 255

Question 11

Define Integer type (Integral)

Answer 11

Numbers that are whole numbers without decimal points. It can be negative or positive numbers.

Question 12

Define Floating-point type

Answer 12

Floating-point type is numbers with one or more decimal points. It can be negative or positive numbers.

Question 13

sbyte

Answer 13

signed 8 BIT / 1 byte

-128 to 127

Question 14

short

Answer 14

It occupies 2 bytes / 16-bit memory.

The short data type is a signed integer that can store numbers from -32,768 to 32,767.

Question 15

Signed vs unsigned values

Answer 15

signed means specified as positive or negative, unsigned means positive by default

Question 16

Converting a value type to a reference type in an object is called BOXING.

Select the correct answer if the text in italics does not make the statement correct.

a - no change
b - unboxing
c - upcasting
d - downcasting

Answer 16

A - No change

changing a value type to a reference type = boxing

Question 17

Value Type

Answer 17

A variable of a value type contains an instance of the type.

It is stored in the stack with both its name and value in the same entry.

Question 18

Reference Type

Answer 18

contains a reference to an instance of the type (in heap memory)

An example is a string. The NAME of the variable is stored in the stack, which points to its memory address in the heap.

Question 19

Upcasting

Answer 19

Upcasting is an operation that creates a base class reference from a subclass reference. (subclass -> superclass)

(i.e. Manager -> Employee)

Example:

Employee emp = (Employee)mgr; //mgr is Manager

Question 20

Downcasting

Answer 20

Downcasting is an operation that creates a subclass reference from a base class reference. (superclass -> subclass) (i.e. Employee -> Manager)

Example:

if (employee is Manager)
{
Manager m = (Manager)employee;
}

Question 21

GUID

Answer 21

Represents a globally unique identifier (GUID). A GUID is a 128-bit integer (16 bytes) that can be used across all computers and networks wherever a unique identifier is required. Such an identifier has a very low probability of being duplicated.

Question 22

for loop

Answer 22

When you know exactly how many times you want to loop through a block of code, use the for loop instead of a while loop.

for (int i = 0; i < 5; i++)
{
Console.WriteLine(i);
}

Statement 1 sets a variable before the loop starts (int i = 0).

Statement 2 defines the condition for the loop to run (i must be less than 5). If the condition is true, the loop will start over again, if it is false, the loop will end.

Statement 3 increases a value (i++) each time the code block in the loop has been executed.

Question 23

foreach loop

Answer 23

used exclusively to loop through elements in an array:

string[] cars = {"Volvo", "BMW", "Ford", "Mazda"};
foreach (string i in cars) 
{
  Console.WriteLine(i);
}

Question 24

while loop

Answer 24

The while loop loops through a block of code as long as a specified condition is True

int i = 0;
while (i < 5) 
{
  Console.WriteLine(i);
  i++;
}

Question 25

The do/while loop

Answer 25

The do/while loop is a variant of the while loop. This loop will execute the code block once, before checking if the condition is true, then it will repeat the loop as long as the condition is true.

int i = 0;
do 
{
  Console.WriteLine(i);
  i++;
}
while (i < 5);

Question 26

Which statements can you use to exit a while, do, for or foreach loop?

• break
• continue
• goto
• throw
• reurn

Answer 26

• break
• goto
• throw
• reurn

Question 27

Break statement:

Answer 27

At any point within the while, do, for or foreach statement blocks, you can break out of the loop by using the break statement.

Question 28

Continue statement:

Answer 28

You can step directly to the evaluation of the while, do, for or foreach expression by using the continue statement.
If the expression evaluates to true, execution continues at the first statement in the loop. Otherwise, execution continues at the first statement after the loop.

Question 29

The goto statement

Answer 29

The goto statement transfers the program control directly to a labeled statement.

A common use of goto is to transfer control to a specific switch-case label or the default label in a switch statement.

The goto statement is also useful to get out of deeply nested loops.

class SwitchTest
{
    static void Main()
    {
        Console.WriteLine("Coffee sizes: 1=Small 2=Medium 3=Large");
        Console.Write("Please enter your selection: ");
        string s = Console.ReadLine();
        int n = int.Parse(s);
        int cost = 0;
        switch (n)
        {
            case 1:
                cost += 25;
                break;
            case 2:
                cost += 25;
                goto case 1;
            case 3:
                cost += 50;
                goto case 1;
            default:
                Console.WriteLine("Invalid selection.");
                break;
        }
        if (cost != 0)
        {
            Console.WriteLine($"Please insert {cost} cents.");
        }
        Console.WriteLine("Thank you for your business.");

    // Keep the console open in debug mode.
    Console.WriteLine("Press any key to exit.");
    Console.ReadKey();
} }

Question 30

The return statement

Answer 30

The return statement terminates execution of the method in which it appears and returns control to the calling method. It can also return an optional value. If the method is a void type, the return statement can be omitted.

If the return statement is inside a try block, the finally block, if one exists, will be executed before control returns to the calling method.

class ReturnTest
{
    static double CalculateArea(int r)
    {
        double area = r * r * Math.PI;
        return area;
    }
...

Question 31

The Throw Statement

Answer 31

Signals the occurrence of an exception during program execution.

throw [e];

Question 32

What is the purpose of a finally block in exception handling? Select all that apply.

• execute clean up code and release resources.
• execute code only when an exception is thrown
• Code in a finally block is executed even if an exception is not thrown
• to conclude the execution of an application
• to break out of the error handler

Answer 32

• execute clean up code and release resources.

- Code in a finally block is executed even if an exception is not thrown

Question 33

What is the purpose of the throw keyword? Select all that apply:

• To move error handling to a separate thread
• To stop the processing of code
• To raise exceptions
• To re-throw exceptions as a different type

Answer 33

• to raise exceptions

- to re-throw exceptions as a different type