Values and Data Types ICSE Class 10 Computer Applications

What Values and Data Types is about

Weightage: CISCE publishes no chapter weightage. Section A (40 marks) is compulsory: 1-mark MCQs and 2-mark short answers including output and error questions; in Section B you answer any four of six 15-mark programming questions written in Java.Source: CISCE ICSE Computer Applications (661) specimen paper structure for 2027

Key concepts

Character set, ASCII and Unicode

The character set of Java is the set of characters it recognises: letters (A-Z, a-z), digits (0-9), special symbols and white space. Java uses Unicode, a 16-bit code that can represent characters of almost all world languages (65,536 codes in its basic form). The first 128 Unicode codes are the same as ASCII (American Standard Code for Information Interchange), a 7-bit code.

Useful ASCII codes: 'A' to 'Z' = 65 to 90; 'a' to 'z' = 97 to 122; '0' to '9' = 48 to 57; space = 32. The gap between an upper-case letter and its lower-case form is 32 ('a' − 'A' = 32).

A char used in arithmetic is promoted to its integer code: 'A' + 1 = 66.

Worked example

(1 mark) What is printed by System.out.println('Z' + 32); ?
(a) z
(b) Z
(c) 122
(d) 154

Try it first, then show the solutionSolution

1. 'Z' is 90; char + int gives int 122, printed as a number.

Answer: (c) 122

Escape sequences

An escape sequence is a backslash (\) followed by a character, used inside a string or char literal to represent a special character. The syllabus lists:
\n - new line
\t - horizontal tab
\\ - backslash
\" - double quote
\' - single quote

Example: System.out.println("She said, \"Hi!\"\nBye"); prints
She said, "Hi!"
Bye

Note the backslash (\), not the forward slash (/): "/n" prints the two characters / and n.

Worked example

(2 marks) Give the output: System.out.println("Tab\there\\ok\'s");

Try it first, then show the solutionSolution

1. \t gives a tab between Tab and here - 1 mark.
2. \\ prints one backslash; \' prints a single quote - 1 mark.

Answer: Tab here\ok's (a tab space after Tab)

Tokens: keywords, identifiers, literals, punctuators, operators

A token is the smallest individual unit of a program.
(1) Keywords: reserved words with special meaning that cannot be used as names: class, int, double, if, else, for, while, new, return, void, static, public, private, final, break.
(2) Identifiers: names given by the programmer to variables, methods, classes and arrays. Rules: may contain letters, digits, underscore (_) and dollar sign; must not start with a digit; no spaces; cannot be a keyword; case sensitive. Valid: total, _rate, mark2; invalid: 2mark, my total, class.
(3) Literals (constants): fixed values written in the program: integer (25), floating-point (3.14, 2.5f), character ('A'), string ("Java"), boolean (true, false), and null.
(4) Punctuators (separators): ; , . ( ) { } [ ]
(5) Operators: symbols that perform operations: + - * / % = == && etc.

Worked example

(2 marks) Classify as keyword, identifier or literal: (a) while (b) totalMarks (c) 'x' (d) 45.6

Try it first, then show the solutionSolution

1. (a) keyword; (b) identifier - 1 mark.
2. (c) character literal; (d) floating-point literal - 1 mark.

Answer: (a) keyword, (b) identifier, (c) character literal, (d) floating-point (real) literal.

Variables, constants and primitive data types

A variable is a named memory location whose value can change: int age = 15;. A constant is a variable whose value cannot change once assigned, declared with final: final double PI = 3.14159;.

Primitive (built-in) data types and sizes:
byte - 1 byte (8 bits), whole numbers −128 to 127
short - 2 bytes (16 bits)
int - 4 bytes (32 bits), default for whole numbers
long - 8 bytes (64 bits), literal with L, e.g. 9000000000L
float - 4 bytes (32 bits), literal with f, e.g. 2.5f
double - 8 bytes (64 bits), default for decimals
char - 2 bytes (16 bits), one Unicode character in single quotes
boolean - true or false only (holds one bit of information; Java does not fix its storage size)

Non-primitive (reference, composite) types: class, array, interface and String. They are built from primitives, are user-defined or library-defined, and hold references to objects.

Memory used by an array = number of elements × size of each: char c[4][3] uses 12 × 2 = 24 bytes; double x[] = {2.5, 4.5, 5.5, 6.4} uses 4 × 8 = 32 bytes.

Worked example

(1 mark) How many bytes does a character array of 4 rows and 3 columns occupy?
(a) 12
(b) 24
(c) 48
(d) 96

Try it first, then show the solutionSolution

1. 4 × 3 = 12 elements; each char is 2 bytes; 12 × 2 = 24.

Answer: (b) 24

Type conversion: implicit and explicit

Implicit (automatic, widening) conversion: Java converts a smaller type to a larger one by itself when they are mixed in an expression or assigned, with no loss of data. Order: byte → short → int → long → float → double; char → int. Examples: double d = 5; gives 5.0; 'A' + 2 gives 67 (int); 7 / 2.0 gives 3.5 because 7 is widened to double.

Explicit conversion (type casting, narrowing): the programmer forces a conversion by writing the type in brackets; it may lose data. Examples: (int) 7.9 gives 7 (decimal part dropped, not rounded); (char) 98 gives 'b'; (int) 'a' gives 97; (double) 7 / 2 gives 3.5.

Integer division: when both operands are int, the result is int: 7 / 2 = 3, and double d = 7 / 2; gives 3.0 (division happens before widening).

String joining: + with a String concatenates: "A" + 'B' gives "AB"; 1 + 2 + "3" gives "33" (left to right: 1 + 2 = 3, then "3" + "3"); "1" + 2 + 3 gives "123".

Worked example

(2 marks) String s1 = "45.50"; String s2 = "54.50"; double d1 = Double.parseDouble(s1); double d2 = Double.parseDouble(s2); int x = (int)(d1 + d2); What is x?

Try it first, then show the solutionSolution

1. parseDouble converts the strings: d1 = 45.5, d2 = 54.5; sum = 100.0 - 1 mark.
2. (int) 100.0 = 100 - 1 mark.

Answer: x = 100

Values and Data Types in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Primitive Data Types and Type Conversion
• Tokens, Identifiers, Literals and Escape Sequences

Values and Data Types: syntax and key facts

Sizes (bytes)

byte 1, short 2, int 4, long 8, float 4, double 8, char 2, boolean true/false

Bits = bytes × 8.

ASCII anchors

'A' = 65, 'a' = 97, '0' = 48, space = 32; lower − upper = 32

char + int → int.

Widening order

1. 1.byte
2. 2.short
3. 3.int
4. 4.long
5. 5.float
6. 6.double; char
7. 7.int

Implicit; narrowing needs a cast.

Array memory

bytes = number of elements × size of element type

double[4] = 32 bytes; char[4][3] = 24 bytes.

Escape sequences

\n new line, \t tab, \\ backslash, \" double quote, \' single quote

Backslash, not slash.

How the board asks Values and Data Types

The question patterns to expect, and the method that works for each.

Tricks to remember Values and Data Types

Short memory aids. Say each one aloud once, then use it on a question the same day.

• B-S-I-L-F-D = 1-2-4-8-4-8

  byte 1, short 2, int 4, long 8, float 4, double 8; char 2.

  Use it when: Sizes in bytes.

• 65-97-48

  A is 65, a is 97, zero is 48.

  Use it when: ASCII questions.

• Back for escape

  Escape needs the backslash, which leans back: \n.

  Use it when: Escape sequences.

Values and Data Types: board-level solved questions

Ordered from board level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section B style)

Read the situation, then answer every part. In the board paper this is a 10-mark question split into 2 + 3 + 5 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Values and Data Types

The slips examiners see most often, and what to write instead.

• ✗Mistake: Unsure of typecasting and ASCII values

  The 2024 examiners noted candidates lacked clarity on (char)98 and were unsure when options were letters.

  ✓Do this: Memorise 65, 97 and 48 and count from them.

  Usually costs: 1 mark.

• ✗Mistake: Writing z or 154 for 'Z' + 32

  The 2025 examiners reported confusion over implicit casting of char in arithmetic.

  ✓Do this: char + int gives an int; println prints the number 122.

  Usually costs: 1 mark.

• ✗Mistake: Forward slash in escape sequences

  In 2024 candidates confused / with \; in 2025 punctuation and escape sequences confused them.

  ✓Do this: Escape sequences always use the backslash.

  Usually costs: 1 mark.

• ✗Mistake: Rounding before adding, or concatenating strings

  In the 2024 parseDouble question candidates rounded first, ignored the cast or joined the strings.

  ✓Do this: Convert with parseDouble, add as doubles, then cast the sum.

  Usually costs: 1 to 2 marks.

• ✗Mistake: Wrong bytes for arrays

  In 2024 some wrote 48 for a 4 × 3 char array; in 2025 some miscounted a double array.

  ✓Do this: Elements × size of type (char 2, double 8).

  Usually costs: 1 mark.

Practice questions on Values and Data Types

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQBoard level

   Which of these is an escape sequence?
   (a) /n
   (b) \t
   (c) /t
   (d) //n

   Hint

   Backslash.

   Answer

   (b) \t

2. Q2 · 1 mark · MCQBoard level

   The size of a char in Java is:
   (a) 1 byte
   (b) 2 bytes
   (c) 4 bytes
   (d) 8 bytes

   Hint

   Unicode.

   Answer

   (b) 2 bytes

3. Q3 · 1 mark · MCQBoard level

   double x[] = {2.5, 4.5, 5.5, 6.4}; occupies:
   (a) 16 bytes
   (b) 4 bytes
   (c) 8 bytes
   (d) 32 bytes

   Hint

   4 × 8.

   Answer

   (d) 32 bytes

4. Q4 · 2 marks · Very short answerBoard level

   Distinguish between implicit and explicit type conversion with one example each.

   Hint

   Automatic vs cast.

   Answer

   Implicit conversion is done automatically by Java from a smaller to a larger type, e.g. double d = 10; stores 10.0. Explicit conversion (type casting) is forced by the programmer, possibly losing data, e.g. int n = (int) 9.8; stores 9.

5. Q5 · 2 marks · Very short answerHarder board level

   State whether valid or invalid identifiers: (a) _sum (b) total marks (c) Class (d) 3rd

   Hint

   Case-sensitive keyword check.

   Answer

   (a) valid (b) invalid: contains a space (c) valid: Class differs from the keyword class (d) invalid: starts with a digit.

6. Q6 · 2 marks · Very short answerHarder board level

   Give the output: char c = 'D'; int n = c + 3; System.out.println(n); System.out.println((char) n);

   Hint

   D is 68.

   Answer

   71
   G

7. Q7 · 2 marks · Short answerHOTS / competency

   Give the output: System.out.println(10 / 4 * 4 + " " + 10 / 4.0 * 4);

   Hint

   Integer division first.

   Answer

   8 10.0 (10 / 4 = 2, × 4 = 8; 10 / 4.0 = 2.5, × 4 = 10.0)

8. Q8 · 15 marks · Long answerHOTS / competency

   Write a program to accept a digit character (for example '7') and print the integer value it represents and that value doubled, using type conversion only.

   Hint

   Subtract '0' (48).

   Answer

   import java.util.Scanner;
   class DigitValue
   {
   public static void main(String args[])
   {
   Scanner sc = new Scanner(System.in);
   System.out.print("Enter a digit: ");
   char ch = sc.next().charAt(0);
   int value = ch - '0';
   System.out.println("Value = " + value);
   System.out.println("Double = " + (value * 2));
   }
   }
   Trace with '7': '7' is 55, 55 − 48 = 7; Value = 7, Double = 14.

9. Q9 · 2 marks · Short answerHOTS / competency

   Why does double d = 7 / 2; store 3.0 and not 3.5?

   Hint

   Order of events.

   Answer

   Both 7 and 2 are int, so 7 / 2 is integer division giving 3; only then is 3 widened to 3.0 for the double variable.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.ASCII code of 'a'?Show answer

   97

2. 2.Size of double in bits?Show answer

   64

3. 3.Is String primitive?Show answer

   No; it is a class (non-primitive).

4. 4.(int) 9.99 = ?Show answer

   9

5. 5.Name the five types of tokens.Show answer

   Keywords, identifiers, literals, punctuators, operators.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Unicode 16-bit; ASCII 7-bit; A 65, a 97, 0 48.
• ☐\n \t \\ \" \' with backslash.
• ☐Tokens: keywords, identifiers, literals, punctuators, operators.
• ☐byte 1, short 2, int 4, long 8, float 4, double 8, char 2 bytes; boolean true/false.
• ☐Widening is automatic; narrowing needs (type) and truncates.
• ☐int / int gives int; + with a String joins.

Values and Data Types: frequently asked questions