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Chapter 3

Values and Data Types

Class 9 - APC Understanding Computer Applications with BlueJ


Multiple Choice Questions

Question 1

A constant which gives the exact representation of data is called

  1. Variable
  2. Literal ✓
  3. Identifier
  4. Character

Question 2

A word used in a high level language which has a special meaning attached to it is called

  1. Class
  2. Identifier
  3. Keyword ✓
  4. Literal

Question 3

A character literal is assigned to a:

  1. Char variable ✓
  2. Char type literal
  3. String variable
  4. String literal

Question 4

A character literal is enclosed in:

  1. ' ' ✓
  2. " "
  3. : :
  4. { }

Question 5

A set of characters is assigned to:

  1. String variable ✓
  2. Static variable
  3. Boolean variable
  4. None

Question 6

The ASCII codes of upper case alphabets range from:

  1. 65 - 90 ✓
  2. 60 - 85
  3. 65 - 91
  4. 97 - 122

Question 7

Which of the following results in integer type?

  1. 11.4F/3.2D
  2. 13.8F/4.6F;
  3. 12/3 ✓
  4. none

Question 8

Which of the following is non-primitive data?

  1. char
  2. long
  3. object ✓
  4. short

Question 9

Which of the following type is an exact representation of fractional values?

  1. char
  2. double ✓
  3. byte
  4. String

Question 10

Boolean Data is used to test a particular condition i.e. true or false. Which of the following is a correct representation?

  1. boolean m=true ✓
  2. boolean m='true'
  3. boolean m="true"
  4. none

Fill in the blanks

Question 1

The character sets of Java is like alphabets of English language.

Question 2

A standard encoding system way of representing characters is Unicode.

Question 3

ASCII code is decimal number to represent a character.

Question 4

Each individual component of a Java statement is known as token.

Question 5

In Java, the constants are also called literals.

Question 6

Assignment operator is used to store a value in the variable.

Question 7

The comma, exclamation, question mark etc., are termed as Separators in Java language.

Question 8

An element of Java program that is used to identify a class, function or value is called as identifier.

Question 9

Integer type value occupies 4 bytes in the memory.

Question 10

A Java expression that contains all the elements of same data type is pure expression.

Write short answers

Question 1

What do you mean by data type?

Data types are used to identify the type of data a memory location can hold and the associated operations of handling it.

Question 2

Define variable with an example.

A variable represents a memory location through a symbolic name which holds a known or unknown value of a particular data type. This name of the variable is used in the program to refer to the stored value.
Example:
int mathScore = 95;

Question 3

What do you mean by constant? Explain with an example.

The keyword final before a variable declaration makes it a constant. Its value can't be changed in the program.
Example:
final int DAYS_IN_A_WEEK = 7;

Question 4

State two kinds of data types.

Two kinds of data types are:

  1. Primitive Datatypes.
  2. Non-Primitive Datatypes.

Question 5

What do you understand by Token? Name different types of tokens.

A token is the smallest element of a program that is meaningful to the compiler. The different types of tokens in Java are:

  1. Identifiers
  2. Literals
  3. Operators
  4. Separators
  5. Keywords

Question 6

What are the rules to assign a variable in a Java programming?

  1. Name of the variable should be a sequence of alphabets, digits, underscore and dollar sign characters only.
  2. It should not start with a digit.
  3. It should not be a keyword or a boolean or null literal.

Question 7

Explain the term 'type casting'?

The process of converting one predefined type into another is called type casting.

Question 8

Perform the following:

(a) Assign the value of pie (3.142) to a variable with the requisite data type.

double pi = 3.142;

(b) Assign the value of (1.732) to a variable with the requisite data type.

double x = 1.732;

Question 9

Distinguish between:

(a) Integer and floating constant

Integer ConstantFloating Constant
Integer Constants represent whole number values like 2, -16, 18246, 24041973, etc.Floating Constants represent fractional numbers like 3.14159, -14.08, 42.0, 675.238, etc.
Integer Constants are assigned to variables of data type — byte, short, int, long, charFloating Constants are assigned to variables of data type — float, double

(b) Token and Identifier

TokenIdentifier
A token is the smallest element of a program that is meaningful to the compiler.Identifiers are used to name things like classes, objects, variables, arrays, functions an so on.
Tokens in Java are categorised into 5 types — Keywords, Identifiers, Literals, Punctuators, Operators.Identifier is a type of token in Java.

(c) Character and String constant

Character ConstantString Constant
Character Constants are written by enclosing a character within a pair of single quotes.String Constants are written by enclosing a set of characters within a pair of double quotes.
Character Constants are assigned to variables of type char.String Constants are assigned to variables of type String.

(d) Character and Boolean literal

Character LiteralBoolean Literal
Character literals are written by enclosing a character within a pair of single quotes.A boolean literal can take only one of the two boolean values represented by the words true or false.
Character literals can be assigned to variables of any numeric data type — byte, short, int, long, float, double, charBoolean literals can only be assigned to variables declared as boolean
Escape Sequences can be used to write character literalsOnly true and false values are allowed for boolean literals

Question 10

Write down the data type of the following:

(a) Integer
int

(b) Long Integer
long

(c) A fractional number
double

(d) A special character
char

Question 11

What do you understand by Boolean type data? Explain with an example.

A boolean data type is used to store one of the two boolean values — true or false. The size of boolean data type is 8 bits or 1 byte.
Example:
boolean bTest = false;

Question 12

What do you understand by primitive data type? Give two examples.

Primitive data types are the basic or fundamental data types used to declare a variable. Examples of primitive data types in Java are byte, short, int, long, float, double, char, boolean.

Question 13

Why is it necessary to define data type in Java programming?

Data types tells Java how much memory it should reserve for storing the value. Data types also help in preventing errors as the compiler can check and flag illegal operations at compile time itself.

Question 14

Define the following with an example each:

(a) Implicit type conversion

In implicit type conversion, the result of a mixed mode expression is obtained in the higher most data type of the variables without any intervention by the user. Example:

int a = 10;
float b = 25.5f, c;
c = a + b;

(b) Explicit type conversion

In explicit type conversion, the data gets converted to a type as specified by the programmer. For example:

int a = 10;
double b = 25.5;
float c = (float)(a + b);

Question 15

Define 'Coercion' with reference to type conversion.

In a mixed-mode expression, the process of promoting a data type into its higher most data type available in the expression without any intervention by the user is known as Coercion.
Example:

byte b = 42;
int i = 50000;
double result = b + i;

Question 16

What do you mean by type conversion? How is implicit conversion different from explicit conversion?

The process of converting one predefined type into another is called type conversion. In an implicit conversion, the result of a mixed mode expression is obtained in the higher most data type of the variables without any intervention by the user. For example:

int a = 10;
float b = 25.5f, c;
c = a + b;

In case of explicit type conversion, the data gets converted to a type as specified by the programmer. For example:

int a = 10;
double b = 25.5;
float c = (float)(a + b);

Question 17

In what way is static declaration different from dynamic declaration?

In static declaration, the initial value of the variable is provided as a literal at the time of declaration. For example:

int mathScore = 100;
double p = 1.4142135;
char ch = 'A';

In dynamic declaration, the initial value of the variable is the result of an expression or the return value of a method call. Dynamic declaration happens at runtime. For example:

int a = 4;
int b = Math.sqrt(a);

double x = 3.14159, y = 1.4142135;
double z = x + y;

Question 18

What do you mean by non-primitive data type? Give examples.

A non-primitive data type is one that is derived from Primitive data types. A number of primitive data types are used together to represent a non-primitive data type. Examples of non-primitive data types in Java are Class and Array.

Question 19

Predict the return data type of the following:

(i)

int p; double q;
r = p+q;
System.out.println(r);
Answer

Return data type is double.

(ii)

float m;
p = m/3*(Math.pow(4,3));
System.out.println(p);
Answer

Return data type is double.

Question 20

What are the resultant data types if the following implicit conversions are performed? Show the result with flow lines.

int i; float f; double d; char c; byte b;

(a) i + c/b;

Answer

     i + c/b;
⇒ int + char / byte
⇒ int + char
⇒ int

(b) f/d + c*f;

Answer

     f/d + c*f;
⇒ float / double + char * float
⇒ double + float
⇒ double

(c) i + f - b*c;

Answer

     i + f - b*c;
⇒ int + float - byte * char
⇒ int + float - char
⇒ float - char
⇒ float

(d) (f/i)*c + b;

Answer

     (f/i)*c + b;
⇒ (float / int) * char + byte
⇒ float * char + byte
⇒ float + byte
⇒ float

(e) i + f- c + b/d;

Answer

     i + f- c + b/d;
⇒ int + float - char + byte / double
⇒ int + float - char + double
⇒ float - char + double
⇒ float + double
⇒ double

(f) i/c + f/b;

Answer

     i/c + f/b
⇒ int / char + float / byte
⇒ int + float
⇒ float

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