NEB Class 12 Science Visual Programming Question Paper 2082 (Set D) Nepal

C# stands for C-Sharp.

Implicit conversion widens from smaller to larger type: char < int < float.

The loop runs for i = 0 to 4. When i == 2, continue skips the Write, so 2 is not printed. Output: 0 1 3 4.

A 2D array in C# is declared with a comma inside the brackets: int[,] arr = new int[2, 3];.

A struct is a value type allocated (typically) on the stack; it is destroyed when the variable goes out of scope.

A small, lightweight value type with a couple of fields suits a struct best: representing a 2D coordinate point (x, y) in a graphics application.

A structure groups together related variables, which may be of different types: a collection of variables of different type.

A void pointer has no associated type/size, so pointer arithmetic (incrementing) is not allowed on it: void.

INSERT/UPDATE/DELETE statements that do not return rows are run with ExecuteNonQuery().

An operator is a special symbol that tells the compiler to perform a specific mathematical, relational, logical or bitwise operation on one or more operands (values/variables) and produce a result.

Two types:

1. Arithmetic operators — perform basic mathematical operations (+, -, *, /, %).

int a = 10, b = 3;
Console.WriteLine(a + b);  // 13 (addition)
Console.WriteLine(a % b);  // 1  (modulus / remainder)

2. Relational (comparison) operators — compare two operands and return a bool (==, !=, >, <, >=, <=).

int x = 5, y = 8;
Console.WriteLine(x < y);   // True
Console.WriteLine(x == y);  // False

(Other valid pairs: logical &&, ||, !; assignment =, +=; etc.)

Option 1 — 30 student scores (1D array):

using System;
class Scores {
    static void Main() {
        int[] scores = new int[30];          // initialize array for 30 students
        for (int i = 0; i < 30; i++)
            scores[i] = i + 1;               // sample initialization

        scores[9] = 95;                      // update 10th student (index 9)

        for (int i = 0; i < scores.Length; i++)
            Console.WriteLine("Student " + (i + 1) + ": " + scores[i]);
    }
}

Option 2 — add two 2×2 matrices:

using System;
class MatrixAdd {
    static void Main() {
        int[,] a = { {1, 2}, {3, 4} };
        int[,] b = { {5, 6}, {7, 8} };
        int[,] sum = new int[2, 2];

        for (int i = 0; i < 2; i++)
            for (int j = 0; j < 2; j++)
                sum[i, j] = a[i, j] + b[i, j];

        Console.WriteLine("Sum of matrices:");
        for (int i = 0; i < 2; i++) {
            for (int j = 0; j < 2; j++)
                Console.Write(sum[i, j] + " ");
            Console.WriteLine();
        }
    }
}

Option 1 — 1D vs 2D array:

Option 2 — IndexOf() and two string functions:

• IndexOf() returns the zero-based position of the first occurrence of a specified character or substring; returns -1 if not found.

string s = "Programming";
Console.WriteLine(s.IndexOf('g'));    // 3
Console.WriteLine(s.IndexOf("ram")); // 4

Comparing two other string functions:

• Substring(start, length) — extracts a portion of the string.

Console.WriteLine("Programming".Substring(0, 4)); // "Prog"

• ToUpper() — returns a copy of the string in upper case.

Console.WriteLine("Programming".ToUpper()); // "PROGRAMMING"

Substring() returns part of a string while ToUpper() changes the casing of the whole string; both return a new string without modifying the original (strings are immutable).

A structure (struct) in C# is a value type that groups together related variables (fields) of different data types under a single name. Unlike a class, it is stored on the stack and is suited to small, lightweight data objects.

using System;

struct Book {
    public string Title;
    public string Author;
    public double Price;
}

class Program {
    static void Main() {
        Book b;                       // create an instance
        b.Title = "C# Programming";    // assign values
        b.Author = "John Doe";
        b.Price = 550.0;

        Console.WriteLine("Title : " + b.Title);
        Console.WriteLine("Author: " + b.Author);
        Console.WriteLine("Price : " + b.Price);
    }
}

Advantages of using pointers in C#:

1. Direct memory access — a pointer holds the actual memory address of a variable, allowing direct read/write of that location.
2. Performance / efficiency — avoids copying large data structures by passing addresses, reducing overhead.
3. Interoperability — enables calling unmanaged/native (C/C++ Win32) APIs that expect raw memory addresses.
4. Low-level manipulation — supports pointer arithmetic and working with fixed memory buffers.

Scenarios where pointers should be used (inside an unsafe block):

• Interoperating with unmanaged code / native libraries (P/Invoke, COM).
• Performance-critical code such as image/audio/byte-buffer processing where copying must be avoided.
• Working with fixed-size memory buffers or hardware/device-level programming.

Note: pointers in C# require the unsafe keyword and the /unsafe compiler option, and should be used only when managed alternatives are insufficient.

Conditional control statements let a program choose different paths of execution based on whether a condition is true or false.

1. if statement — executes a block only when the condition is true.

if (condition) {
    // statements
}

Real-world: allow login only if the password is correct.

if (password == "admin123")
    Console.WriteLine("Login successful");

2. if...else statement — chooses between two blocks.

if (condition) {
    // true block
} else {
    // false block
}

Real-world: decide pass or fail by marks.

if (marks >= 40)
    Console.WriteLine("Pass");
else
    Console.WriteLine("Fail");

3. if...else if...else (ladder) — tests several conditions in sequence.

if (cond1) { ... }
else if (cond2) { ... }
else { ... }

Real-world: assign grade by marks.

if (marks >= 80) Console.WriteLine("A");
else if (marks >= 60) Console.WriteLine("B");
else if (marks >= 40) Console.WriteLine("C");
else Console.WriteLine("Fail");

4. Nested if — an if placed inside another if for dependent conditions.

if (age >= 18) {
    if (hasLicense)
        Console.WriteLine("Allowed to drive");
}

Real-world: a person can drive only if both adult and licensed.

5. switch statement — selects one of many blocks based on the value of an expression.

switch (expression) {
    case value1: ...; break;
    case value2: ...; break;
    default: ...; break;
}

Real-world: menu selection.

switch (day) {
    case 1: Console.WriteLine("Sunday"); break;
    case 2: Console.WriteLine("Monday"); break;
    default: Console.WriteLine("Invalid"); break;
}

Thus C# provides if, if-else, if-else if ladder, nested if, and switch as conditional control statements.

Option 1 — Steps to connect a C# program to a database (ADO.NET):

1. Add the namespace — using System.Data.SqlClient; (for SQL Server).
2. Create a connection string with server, database and authentication details.
3. Create a SqlConnection object using the connection string.
4. Open the connection with con.Open().
5. Create a command (SqlCommand) with the SQL query and connection.
6. Execute the command — ExecuteNonQuery() for INSERT/UPDATE/DELETE, ExecuteReader() for SELECT.
7. Process the result (read rows if any).
8. Close the connection with con.Close().

using System;
using System.Data.SqlClient;

class DbDemo {
    static void Main() {
        string cs = "server=.;database=SchoolDB;Trusted_Connection=True;";
        SqlConnection con = new SqlConnection(cs);
        con.Open();
        SqlCommand cmd = new SqlCommand("INSERT INTO Student VALUES('Ram', 85)", con);
        int rows = cmd.ExecuteNonQuery();
        Console.WriteLine(rows + " record inserted");
        con.Close();
    }
}

Option 2 — Four methods of the Array class with program:

• Array.Sort() — sorts elements in ascending order.
• Array.Reverse() — reverses the order of elements.
• Array.IndexOf() — returns the index of a given value.
• Array.Clear() — sets a range of elements to their default value (0/null).

using System;
class ArrayMethods {
    static void Main() {
        int[] a = { 40, 10, 30, 20 };

        Array.Sort(a);                 // 10 20 30 40
        Console.WriteLine(string.Join(" ", a));

        Array.Reverse(a);              // 40 30 20 10
        Console.WriteLine(string.Join(" ", a));

        int pos = Array.IndexOf(a, 20); // index of value 20
        Console.WriteLine("Index of 20: " + pos);

        Array.Clear(a, 0, 2);          // first two set to 0
        Console.WriteLine(string.Join(" ", a));
    }
}

(Other valid Array methods: Array.Copy(), Array.Find(), Array.Length.)