Program Coding ICSE Class 8: Identifiers, Data Types, Operators and if-else in Java

What Program Coding is about

Weightage: CISCE publishes no question paper, marking scheme or chapter weightage for Class VIII Computer Studies: your school sets and marks the exam. Program Coding sits in the Theme: Program Coding theme of the CISCE Curriculum for Upper Primary Classes (VI-VIII).Source: CISCE Curriculum for Upper Primary Classes (VI-VIII), RDCD 2016

Key concepts

Structure of a program; compiling and executing

A simple Java program:

// My first Java program
class Welcome
{
    public static void main(String args[])
    {
        System.out.println("Welcome to Java");
        System.out.println("I am in Class 8");
    }
}

Output (as run):

Welcome to Java
I am in Class 8

• class Welcome names the program; the code goes between the curly braces { }.
• main is where the program starts running.
• System.out.println(...) prints and moves to a new line; System.out.print(...) prints and stays on the same line.
• Every statement ends with a semicolon ;.
• // starts a comment, which the computer ignores; it explains code to people.

Compiling and executing:

• The program you write is the source code. A compiler checks it for syntax errors (spelling and grammar mistakes in code) and translates it. In Java, the compiler (javac) produces bytecode, which the Java Virtual Machine (JVM) then executes (runs).
• In BlueJ: write the class, click Compile; if there are no errors, right-click the class and choose void main(String[] args) to run it.
• Errors: syntax errors (missing semicolon, wrong spelling) are caught when compiling; logical errors (wrong formula) give wrong answers and must be found by testing.

Worked example

A student types System.out.println("Hello") without a semicolon and also writes Println with a capital P. When are these errors found, and what kind are they?

Try it first, then show the solutionSolution

1. Both are syntax errors: Java needs a semicolon after each statement, and it is case-sensitive, so Println is not the same as println.
2. The compiler reports them when the program is compiled, before it can run.

Answer: Syntax errors, found at compile time.

Identifiers, literals and data types

Identifiers are the names given to variables, classes and other parts of a program, such as age, totalMarks, Welcome.

Naming rules (Java):

• May contain **letters, digits, underscore _ and dollar sign**.
• Must not start with a digit (2marks is invalid; marks2 is valid).
• No spaces or other symbols (total marks, marks% are invalid).
• Must not be a keyword (reserved word such as int, class, if).
• Case-sensitive: Age and age are different.
• Good practice: meaningful names such as area, studentName.

Literals are fixed values written directly in the program:

Literal	Examples
Integer	25, -7, 0
Real (floating-point)	3.14, -0.5, 152.5f
Character	'A', '7' (one character in single quotes)
String	"Riya", "Class 8" (text in double quotes)
Boolean	true, false

Data types tell the computer what kind of value a variable holds and how much memory it needs:

Type	Holds	Size	Example
int	whole numbers	4 bytes	int age = 13;
float	decimal numbers (less precise)	4 bytes	float height = 152.5f;
double	decimal numbers (more precise)	8 bytes	double pi = 3.14159;
char	a single character	2 bytes	char grade = 'A';
boolean	true or false	(1 bit of information)	boolean passed = true;
String	text (a class, not a basic type)	varies	String name = "Riya";

Why different data types? To save memory (no need for 8 bytes to store an age), to store values correctly (decimals need float or double; text needs String), and to let the computer check errors (you cannot store "ten" in an int).

Worked example

Which identifiers are valid? (i) total_marks (ii) 2ndTerm (iii) class (iv) my name (v) area1

Try it first, then show the solutionSolution

1. Valid: (i) letters and underscore; (v) letters then a digit.
2. Invalid: (ii) starts with a digit; (iii) keyword; (iv) contains a space.

Answer: Valid: (i) and (v)

Declaring and initialising variables

A variable is a named memory location whose value can change while the program runs.

• Declaration: telling the computer the variable's type and name: int age;
• Initialisation: giving it its first value: age = 13;
• Both together: int age = 13;
• Several of one type: int a = 17, b = 5;

Program (as run):

class DataTypes
{
    public static void main(String args[])
    {
        int age = 13;
        float height = 152.5f;
        double pi = 3.14159;
        char grade = 'A';
        boolean passed = true;
        String name = "Riya";
        System.out.println("Name: " + name);
        System.out.println("Age: " + age);
        System.out.println("Height: " + height);
        System.out.println("Pi: " + pi);
        System.out.println("Grade: " + grade);
        System.out.println("Passed: " + passed);
    }
}

Output:

Name: Riya
Age: 13
Height: 152.5
Pi: 3.14159
Grade: A
Passed: true

The + between text and a value joins them into one string. A float literal needs an f at the end (152.5f); without it Java treats the number as a double.

Worked example

Write statements to declare and initialise a variable for (i) the number of students, 40 (ii) the price of a pen, ₹12.50 (iii) a section letter, B.

Try it first, then show the solutionSolution

1. (i) Whole number: int students = 40; (ii) Decimal: double price = 12.50;
2. (iii) One character: char section = 'B';

Answer: int students = 40; double price = 12.50; char section = 'B';

Arithmetic, relational, logical and assignment operators

Program (as run) with int a = 17, b = 5;:

System.out.println(a + b);          // 22
System.out.println(a - b);          // 12
System.out.println(a * b);          // 85
System.out.println(a / b);          // 3   (int / int drops the decimal part)
System.out.println(a % b);          // 2   (remainder)
System.out.println(17.0 / 5);       // 3.4 (a decimal operand gives a decimal answer)
System.out.println(a > b);          // true
System.out.println(a == b);         // false
System.out.println(a != b);         // true
System.out.println(a > 10 && b > 10); // false
System.out.println(a > 10 || b > 10); // true
System.out.println(!(a > b));       // false

Group	Operators	Result
Arithmetic	+ - * / %	a number; % gives the remainder
Relational	> < >= <= == (equal to) != (not equal to)	true or false
Logical	&& (AND: both true), OR, written as two vertical bars (at least one true), ! (NOT: reverses)	true or false
Assignment	=	stores the value on the right in the variable on the left

Assignment (as run): int x = 10; x = x + 5; makes x 15; then x = x * 2; makes it 30. x = x + 5 is not an equation; it means 'take x, add 5, store the result back in x'.

Do not confuse = (assign) with == (compare).

Order: *, /, % before +, -; brackets first. With int y = 7;, y % 3 + y / 2 = 1 + 3 = 4 (as run).

Joining strings (as run): "Sum = " + 3 + 4 prints Sum = 34 (text first, so each number is joined as text), but "Sum = " + (3 + 4) prints Sum = 7.

Worked example

Give the output (as run): int p = 25, q = 4; then print p / q and p % q on one line, p / q stored in a double, and p + q * 2.

Try it first, then show the solutionSolution

1. p / q = 6 (integer division), p % q = 1: prints 6 1.
2. double d = p / q; stores 6 first, so prints 6.0. p + q * 2 = 25 + 8 = 33.

Answer: 6 1, then 6.0, then 33

Taking input with Scanner

To make programs work for any values, read input from the keyboard using the Scanner class.

import java.util.Scanner;
class Interest
{
    public static void main(String args[])
    {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter principal: ");
        double p = sc.nextDouble();
        System.out.print("Enter rate: ");
        double r = sc.nextDouble();
        System.out.print("Enter time in years: ");
        double t = sc.nextDouble();
        double si = p * r * t / 100;
        double amt = p + si;
        System.out.println("Simple interest = " + si);
        System.out.println("Amount = " + amt);
    }
}

Run with 5000, 8 and 3: Simple interest = 1200.0 and Amount = 6200.0.

• import java.util.Scanner; makes the Scanner class available.
• sc.nextInt() reads an int; sc.nextDouble() a double; sc.next() one word; sc.nextLine() a whole line.
• A double result is printed with .0 when it is a whole number.

Worked example

Which Scanner method would you use to read (i) a number of students (ii) a temperature like 36.6 (iii) a one-word city name?

Try it first, then show the solutionSolution

1. (i) Whole number: nextInt(). (ii) Decimal: nextDouble().
2. (iii) One word: next().

Answer: nextInt(), nextDouble(), next()

Decision making: if, if-else and the if-else-if ladder

if: runs a statement only when the condition is true.

if (n > 0)
    System.out.println("Positive");

if-else: chooses between two paths (as run: 27 → 27 is odd, −4 → -4 is even).

if (n % 2 == 0)
    System.out.println(n + " is even");
else
    System.out.println(n + " is odd");

if-else-if ladder: chooses one of many; conditions are checked from the top, the first true one runs and the rest are skipped.

if (m >= 90)
    g = 'A';
else if (m >= 75)
    g = 'B';
else if (m >= 60)
    g = 'C';
else
    g = 'D';

As run: 82 → B, 90 → A, 59 → D.

Rules:

• The condition goes in brackets and must be true or false.
• No semicolon after if (condition).
• Without braces, only the first statement after if or else belongs to it. Use { } for more than one statement.

Braces trap (as run): int m = 10; if (m > 5) m = m + 1; m = m * 2; prints 22: only m = m + 1 belongs to the if; m = m * 2 always runs. Similarly, with n = -4, if (n > 0) System.out.println("Positive"); System.out.println("Done"); prints only Done.

Worked example

In the grade ladder above, why is the second condition written as m >= 75 and not m >= 75 && m < 90?

Try it first, then show the solutionSolution

1. The ladder reaches else if (m >= 75) only when m >= 90 was false, so m is already below 90.
2. Repeating m < 90 is unnecessary (though not wrong).

Answer: Because the earlier condition has already ruled out 90 and above.

Program Coding 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

• if, if-else and the if-else-if Ladder in Java
• Java Program Structure, Identifiers, Data Types and Variables
• Operators, Expressions and Input with Scanner in Java

Program Coding: syntax and key facts

Program skeleton

class Name { public static void main(String args[]) { statements; } }

Execution starts in main.

Declaration and initialisation

type name = value; e.g. int age = 13;

float literals need f: 152.5f.

Integer division and remainder

17 / 5 gives 3; 17 % 5 gives 2; 17.0 / 5 gives 3.4

int / int drops the fraction.

Relational and logical

> < >= <= == != give true/false; && AND, || OR, ! NOT

= assigns; == compares.

Selection

if (c) s1; / if (c) s1; else s2; / if (c1) s1; else if (c2) s2; else s3;

First true condition wins in a ladder.

Program Coding: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

How the school exam asks Program Coding

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

Tricks to remember Program Coding

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

• No digit first, no space, no keyword

  The three 'no's of naming identifiers (and remember: case matters).

  Use it when: Identifier rules.

• % is the leftover

  17 % 5: five goes three times into 17, leftover 2.

  Use it when: Remainder operator.

• One = gives, two == ask

  = gives a value; == asks 'are these equal?'.

  Use it when: Assignment versus comparison.

• Ladder: first true wins

  Climb from the top; stop at the first true rung.

  Use it when: if-else-if ladder.

• No braces, one statement

  Without { }, if controls just the next statement.

  Use it when: Avoiding the braces trap.

Program Coding: exam-level solved questions

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

int x = 8;
x = x + 4;
System.out.println(x);
x = x * 3;
System.out.println(x);
int y = 11;
int z = y % 4 + y / 3;
System.out.println(z);
System.out.println("Sum = " + 5 + 6);
System.out.println("Sum = " + (5 + 6));
System.out.println(5 + 6 + " is the sum");

int p = 20, q = 6;
double d = p / q;
double e = (double) p / q;
System.out.println(d);
System.out.println(e);
System.out.println(p > q && q > 10);

Case-study practice (Section B style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 6-mark question split into 2 + 2 + 2 marks.

if (bill > 200)
    pay = bill - bill * 5 / 100;
else if (bill > 500)
    pay = bill - bill * 10 / 100;
else
    pay = bill;

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 Program Coding

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

• ✗Mistake: Using = instead of == in a condition

  = assigns; in Java if (x = 5) does not compile for an int x.

  Wrong working

  if (n % 2 = 0)

  Right working

  if (n % 2 == 0)

  ✓Do this: One = gives, two == ask.

  Usually costs: 1 mark, and the program will not compile.

• ✗Mistake: Putting a semicolon after if (condition)

  if (a > b); ends the if at once; the next statement always runs.

  ✓Do this: Never put ; straight after the condition's bracket.

  Usually costs: 1-2 marks.

• ✗Mistake: Forgetting integer division

  7 / 2 is 3 in Java when both are int.

  Wrong working

  7 / 2 = 3.5

  Right working

  7 / 2 = 3; 7.0 / 2 = 3.5

  ✓Do this: Make one operand a decimal if you need a decimal answer.

  Usually costs: 1 mark.

• ✗Mistake: Wrong order in an if-else-if ladder

  A wide condition at the top hides narrower ones below it.

  ✓Do this: Put the most restrictive condition first (bill > 500 before bill > 200).

  Usually costs: Logic marks in programs.

• ✗Mistake: Missing quotes or the f in literals

  char c = A; and float h = 152.5; do not compile.

  ✓Do this: char c = 'A'; and float h = 152.5f;

  Usually costs: 1 mark.

Practice questions on Program Coding

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 · MCQExam level

   Which is a valid identifier?
   (a) 1stName
   (b) first name
   (c) first_name
   (d) int

   Hint

   Digit first, space, keyword.

   Answer

   (c)

2. Q2 · 1 mark · Very short answerExam level

   Name the data type for (i) 25 (ii) 'Y' (iii) true.

   Hint

   Whole number, character, yes/no.

   Answer

   (i) int (ii) char (iii) boolean.

3. Q3 · 2 marks · Short answerExam level

   What is a variable? Write a statement to declare and initialise a variable for the temperature 36.6.

   Hint

   Named memory location.

   Answer

   A variable is a named memory location whose value can change during the program. double temp = 36.6;

4. Q4 · 2 marks · Short answerExam level

   Classify the literals: 45, "45", 4.5, '4'.

   Hint

   Quotes matter.

   Answer

   45 integer; "45" string; 4.5 real; '4' character.

5. Q5 · 1 mark · Assertion-reasonHarder exam level

   Assertion (A): In Java, 9 / 2 evaluates to 4.
   Reason (R): When both operands are integers, Java drops the decimal part of the quotient.
   (a) (A) is true and (R) is false.
   (b) (A) is false and (R) is true.
   (c) Both (A) and (R) are true, and (R) is the correct explanation for (A).
   (d) Both (A) and (R) are true, but (R) is not the correct explanation for (A).

   Hint

   Integer division.

   Answer

   (c)

6. Q6 · 2 marks · Short answerHarder exam level

   With int a = 29, b = 4;, give the value of (i) a % b (ii) a / b (iii) a > 25 || b > 10 (iv) !(a != b).

   Hint

   int / int drops the decimal part; || needs only one true side.

   Answer

   (i) 1 (ii) 7 (iii) true (iv) false.

7. Q7 · 2 marks · Short answerHarder exam level

   Give the output (as run):

   int m = 7;
   if (m % 2 == 0)
       m = m / 2;
       m = m + 10;
   System.out.println(m);

   Hint

   Indentation does not decide which lines belong to the if.

   Answer

   17: without braces only m = m / 2 belongs to the if, and it is skipped because 7 is odd; m = m + 10 always runs despite its indentation, giving 17.

8. Q8 · 2 marks · Short answerHarder exam level

   Distinguish between syntax errors and logical errors with an example of each.

   Hint

   Compile versus wrong answer.

   Answer

   A syntax error breaks the language rules and is caught by the compiler, e.g. a missing semicolon. A logical error lets the program run but gives a wrong result, e.g. writing area = l + b instead of l * b.

9. Q9 · 4 marks · Long answerHarder exam level

   Write a program to input marks and print the grade: A for 90 and above, B for 75 to 89, C for 60 to 74, D below 60. Give the output for 82.

   Hint

   if-else-if ladder.

   Answer

   import java.util.Scanner;
   class Grade
   {
       public static void main(String args[])
       {
           Scanner sc = new Scanner(System.in);
           System.out.print("Enter marks: ");
           int m = sc.nextInt();
           char g;
           if (m >= 90)
               g = 'A';
           else if (m >= 75)
               g = 'B';
           else if (m >= 60)
               g = 'C';
           else
               g = 'D';
           System.out.println("Grade: " + g);
       }
   }

   As run with 82: Grade: B.

10. Q10 · 3 marks · Short answerHarder exam level

    Write the expressions in Java: (i) a is between 10 and 20 inclusive (ii) ch is a vowel 'a' or 'e' (iii) n is not equal to 0.

    Hint

    &&, ||, !=.

    Answer

    (i) a >= 10 && a <= 20 (ii) ch == 'a' || ch == 'e' (iii) n != 0.

11. Q11 · 3 marks · Short answerHarder exam level

    Write a program to input the length and breadth of a rectangle (whole numbers), print its area and perimeter, and print 'It is a square' if they are equal, otherwise 'It is a rectangle'. Give the output for 6 and 4, and for 5 and 5.

    Hint

    Area = l × b; perimeter = 2 × (l + b); then one if-else.

    Answer

    import java.util.Scanner;
    class Rectangle
    {
        public static void main(String args[])
        {
            Scanner sc = new Scanner(System.in);
            System.out.print("Enter length and breadth: ");
            int l = sc.nextInt();
            int b = sc.nextInt();
            System.out.println("Area = " + (l * b));
            System.out.println("Perimeter = " + (2 * (l + b)));
            if (l == b)
                System.out.println("It is a square");
            else
                System.out.println("It is a rectangle");
        }
    }

    As run with 6 and 4: Area = 24, Perimeter = 20, It is a rectangle. With 5 and 5: Area = 25, Perimeter = 20, It is a square.

12. Q12 · 3 marks · Short answerHOTS / competency

    A museum ticket program uses: if (age < 5) price = 0; else if (age < 18) price = 100; else if (age < 60) price = 200; else price = 120;. Give the price for ages 4, 17, 18 and 60, and explain what would go wrong if the first two conditions were swapped.

    Hint

    Ages under 5 are also under 18.

    Answer

    4 → 0; 17 → 100; 18 → 200; 60 → 120. If age < 18 came first, children under 5 would also satisfy it and be charged 100, so the free-entry branch could never run.

13. Q13 · 3 marks · Short answerHOTS / competency

    Predict the output and explain: System.out.println("Total: " + 10 + 20); and System.out.println(10 + 20 + " is the total");

    Hint

    Left to right; text changes + into joining.

    Answer

    Total: 1020 and 30 is the total. In the first, the text comes first, so 10 and 20 are joined as text one after another. In the second, 10 + 20 are added as numbers (30) before meeting the text.

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.What is an identifier?Show answer

   A name given to a variable, class or other program element.

2. 2.Give an example of a string literal.Show answer

   "Hello".

3. 3.Which data type stores a single character?Show answer

   char.

4. 4.What does % do?Show answer

   Gives the remainder of a division.

5. 5.What is the value of !(5 > 3)?Show answer

   false.

6. 6.What does a compiler do?Show answer

   Checks source code for syntax errors and translates it (into bytecode in Java).

7. 7.In a ladder, which branch runs?Show answer

   The first one whose condition is true (else, if none is).

Quick revision checklist

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

• ☐Can you write the skeleton of a Java program from memory?
• ☐Can you spot invalid identifiers?
• ☐Can you choose the right data type for any value?
• ☐Can you predict /, % and string-joining outputs?
• ☐Can you write an if-else-if ladder in the right order?
• ☐Can you explain compile-time (syntax) and logical errors?

Program Coding: frequently asked questions