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Solutions for Computer Applications, Class 9, ICSE
What are escape sequences in Java? Give three examples.
An escape sequence is a set of characters that has a special meaning to the Java compiler. In the escape sequence, a character is preceded by a backslash (\). Some examples of escape sequences are \n, \' and \t.
What is the result of evaluating the following expression?
(1 + 2 * 2) / 2 + 2
(1 + 2 * 2) / 2 + 2 ⇒ (1 + 4) / 2 + 2
⇒ (5) / 2 + 2
⇒ 2 + 2
⇒ 4
What is a token in Java? Name the tokens available in Java.
All characters in a Java program are grouped into symbols called Tokens. As you know, a computer program consists of a set of instructions called statements. A statement is composed of various components. Each individual component of a programming statement is referred to as a token. Keywords, identifiers, Operators, Separators and literals are three tokens in Java.
Why can't you use a keyword as a variable name?
Keywords are reserved words that have a special meaning to the Java compiler. As Java compiler reserves these words for its own use so they are not available as names for variables or methods.
Which of the following are Java keywords?
input, class, public, int, x, y, radius
class, public, int are Java keywords.
What are identifiers in Java? List three identifier formation rules.
Identifiers are used to name different parts of a program such as variables, methods, classes, objects, etc. Three identifier formation rules are:
Explain the following statement — "In Java, total, Total, ToTaL, and TOTAL are all different identifiers."
Java is a case sensitive language. total, Total, ToTaL, and TOTAL have the same set of letters but they differ in the case of these letters. Therefore, Java considers each of them as a different identifier.
How would you print characters like \, ' and " in Java?
We can print characters like \, ' and " using escape sequences i.e. preceding it with a backslash (\) symbol.
Distinguish between the following:
i. Token and Identifier
| Token | Identifier |
|---|---|
| Each individual component of a programming statement is referred to as a token. | Identifiers are fundamental building blocks of the program and are used to name different components of a program such as variables, methods and objects. |
| Tokens in Java are categorised into 5 types — Keywords, Identifiers, Literals, Punctuators, Operators. | Identifier is a type of token in Java. |
ii. Keyword and Identifier
| Keyword | Identifier |
|---|---|
| Keywords have a special meaning for Java compiler. | Identifiers are used to name different components of a program such as variables, methods and objects. |
| Keywords are reserved by the compiler for its own use. | An identifier must not be a Keyword. |
iii. Character and String Constant
| Character Constant | String 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. |
iv. Integer and float Constant
| Integer Constant | Float Constant |
|---|---|
| Integer Constants represent whole number values like 2, -16, 18246, 24041973, etc. | Float 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, char | Float Constants are assigned to variables of data type — float, double |
Distinguish between "A" and 'A'.
"A" is a string literal of length 1 containing the letter A in uppercase whereas 'A' is a character literal having value of A in uppercase.
Describe primitive data types in Java.
Primitive data types are fundamental data types that are an integral part of the Java language and are used to declare a variable.
List the size of primitive data types in Java.
| Data Type | Size in Bytes |
|---|---|
| byte | 1 |
| short | 2 |
| int | 4 |
| long | 8 |
| float | 4 |
| double | 8 |
| char | 2 |
| boolean | 1 |
Which integer and floating point data types take up the same number of bits in computer's memory?
Both, int and float take up 32 bits in memory. Similarly, both long and double take up 64 bits in memory.
What is variable initialisation in Java? What are the default values of the following type of variables:
short, int, long, float, double, and char.
Variable initialisation means assigning value to a variable for the first time. Below are the default values of the different data types:
| Data Type | Default Value |
|---|---|
| short | 0 |
| int | 0 |
| long | 0L |
| float | 0.0f |
| double | 0.0d |
| char | '\u0000' |
ASCII stands for ...........
ASCII is ...........
Extended ASCII is ...........
Which of the following is not a token?
Which of the following is a keyword?
Which of the following is not a legal identifier?
Which of the following is an invalid integer?
Which of the following is not a character literal?
Which of the following punctuator is the statement terminator in Java?
Which of the following is not a primitive data type in Java?
Which of the following is the size of a long data type in Java?
Which of the following is the size of a boolean data type in Java?
Java supports the use of the ASCII character set only.
False
The smallest unit in a Java program is known as token.
True
The Unicode character set uses 8 to 32 bits per character.
True
In an escape sequence, a character is preceded by a forward slash (/).
False
In Java, an identifier cannot begin with a $ sign.
False
The boolean data types are used for storing logical values.
True
Java offers five types of tokens.
True
The char data type reserves 8 bits in memory.
False
If a literal constant contains a decimal point, then it is of the type double by default.
True
The modifier final can be applied to a variable declaration to ensure that the value stored in the variable cannot be changed after the variable has been initialised.
True