Unit 1 (Part B) - C Basics

Part B: 13-Mark Questions

1. Write a C program to find the sum of two numbers using a flowchart and algorithm.

Algorithm

Start
Read two numbers: a, b
Compute sum = a + b
Display sum
Stop

Flowchart Flowchart to sum two numbers

C Program

#include <stdio.h>

int main() {
    int number1;
    int number2;
    int sum;

    printf("Enter the first integer: ");
    scanf("%d", &number1);

    printf("Enter the second integer: ");
    scanf("%d", &number2);

    sum = number1 + number2;

    printf("\nThe sum of %d and %d is: %d\n", number1, number2, sum);
    return 0;
}

Explanation

This program follows an Input-Process-Output (IPO) structure:

Input: It uses printf to prompt the user and scanf to read two integers, storing them in number1 and number2.
Process: It calculates the sum using the assignment statement: sum = number1 + number2;.
Output: It uses printf again to display a formatted message showing the original two numbers and their calculated sum.

2. Elaborate the decision making and looping statements with suitable examples.

1. Decision-Making Statements

Decision-making statements are used to execute parts of code based on specific conditions.

if statement: Executes a block if the condition is true.
```
if (x > 0) {
    printf("Positive number");
}
```

if-else statement: Executes one block if true, and another if false.

if (x % 2 == 0) {
    printf("Even");
} else {
    printf("Odd");
}

Nested if statement: An if statement inside another if statement.

if (x > 0) {
    if (x < 10) {
        printf("x is between 1 and 9");
    }
}

if-else-if ladder: Used to check multiple conditions sequentially.

if (marks >= 90)
    printf("Grade A");
else if (marks >= 75)
    printf("Grade B");
else
    printf("Grade C");

switch statement: Used for multiple choices based on a single variable.

switch (choice) {
    case 1: printf("Addition"); break;
    case 2: printf("Subtraction"); break;
    default: printf("Invalid choice");
}

2. Looping Statements

Looping statements execute a block of code repeatedly.

for loop (Entry-controlled):

for (int i = 1; i <= 5; i++) {
    printf("%d ", i);
}
// Output: 1 2 3 4 5

while loop (Entry-controlled):

int i = 1;
while (i <= 5) {
    printf("%d ", i);
    i++;
}

do-while loop (Exit-controlled): Executes at least once.

int i = 1;
do {
    printf("%d ", i);
    i++;
} while (i <= 5);

3. i. Explain the general structure of a C program with an example.
ii. Write a C program to find the largest of three numbers using ternary operator.

i. General Structure of a C Program

A C program is organized into several sections:

Documentation Section: Comments describing the program.
Preprocessor Section: Includes header files (e.g., #include).
Global Declarations: Global variables and function prototypes.
main() Function: The entry point where program execution begins.
Subprograms / Functions: User-defined functions.

Example Program:

#include <stdio.h> // Preprocessor section

// Global declarations
int globalvar = 10;
void display(); // Function prototype

int main() { // main function section
    int a = 5, b = 10; // Local declarations
    int sum;
    sum = a + b; // Statements
    printf("Sum = %d\n", sum);
    display(); // Function call
    return 0;
}

// Subprogram / function
void display() {
    printf("This is a user-defined function.\n");
}

ii. C Program: Largest of Three Numbers (Ternary Operator)

#include <stdio.h>

int main() {
    int a, b, c, largest;
    
    // Input three numbers
    printf("Enter three numbers: ");
    scanf("%d %d %d", &a, &b, &c);
    
    // Using nested ternary operator
    largest = (a > b) ? ((a > c) ? a : c) : ((b > c) ? b : c);
    
    // Output result
    printf("Largest number = %d\n", largest);
    return 0;
}

Output:

Enter three numbers: 10 20 5
Largest number = 20

Explanation:

First, it checks if a > b.
If true, it checks if a > c. If true, a is largest, else c is largest.
If false (meaning b >= a), it checks if b > c. If true, b is largest, else c is largest.

4. Explain the different types of loops in C with syntax.

Loops are used to execute a block of code repeatedly as long as a condition is true. C has three main types of loops:

1. for loop (Entry-controlled)

Used when the number of iterations is known. The condition is tested before entering the loop.

Syntax:

for (initialization; condition; update) {
    // body of loop
}

Example:

for(int i = 1; i <= 5; i++) {
    printf("%d ", i);
}
// Output: 1 2 3 4 5

2. while loop (Entry-controlled)

Used when the number of iterations is not fixed. The condition is tested before the loop body executes.

Syntax:

initialization;
while (condition) {
    // body of loop
    update;
}

Example:

int i = 1;
while (i <= 5) {
    printf("%d ", i);
    i++;
}
// Output: 1 2 3 4 5

3. do-while loop (Exit-controlled)

The loop body is executed at least once because the condition is tested *after* the body executes.

Syntax:

initialization;
do {
    // body of loop
    update;
} while (condition);

Example:

int i = 1;
do {
    printf("%d ", i);
    i++;
} while (i <= 5);
// Output: 1 2 3 4 5

5. Explain the all-looping statement with example.

Loops are used to execute a block of code repeatedly as long as a condition is true. C provides three main types of loops:

1. for loop (Entry-controlled)

Used when the number of iterations is known. Condition is tested before entering.

Syntax: for (initialization; condition; update) { ... } Example:

for(int i = 1; i <= 5; i++) {
    printf("%d ", i);
}
// Output: 1 2 3 4 5

2. while loop (Entry-controlled)

Used when iterations are not fixed. Condition is tested before executing.

Syntax: while (condition) { ... update; } Example:

int i = 1;
while (i <= 5) {
    printf("%d ", i);
    i++;
}
// Output: 1 2 3 4 5

3. do-while loop (Exit-controlled)

Executes at least once. Condition is tested after the body.

Syntax: do { ... update; } while (condition); Example:

int i = 1;
do {
    printf("%d ", i);
    i++;
} while (i <= 5);
// Output: 1 2 3 4 5

Loop Control Statements

C also has statements to control loop execution:

a) break: Terminates the loop immediately.

for(int i = 1; i <= 5; i++) {
    if(i == 3) break;
    printf("%d ", i);
}
// Output: 1 2

b) continue: Skips the current iteration and moves to the next.

for(int i = 1; i <= 5; i++) {
    if (i == 3) continue;
    printf("%d ", i);
}
// Output: 1 2 4 5

c) goto: Transfers control to a labeled statement. (Use is generally discouraged).

int i = 1;
loop:
if(i <= 3) {
    printf("%d ", i);
    i++;
    goto loop;
}
// Output: 1 2 3

6. Explain the decision-making statement with an example.

Decision-making statements execute code based on conditions.

1. if statement

Executes a block if the condition is true.

Syntax: if (condition) { ... } Example:

int x = 10;
if (x > 0) {
    printf("x is positive");
}
// Output: x is positive

2. if-else statement

Executes one block if true, another if false.

Syntax: if (condition) { ... } else { ... } Example:

int x = 5;
if (x % 2 == 0) {
    printf("Even");
} else {
    printf("Odd");
}
// Output: Odd

3. Nested if statement

An if statement inside another if.

if (x > 0) {
    if (x < 10) {
        printf("x is between 1 and 9");
    }
}
// Output: x is between 1 and 9

4. if-else-if ladder

Used to check multiple conditions sequentially.

int marks = 80;
if (marks >= 90)
    printf("Grade A");
else if (marks >= 75)
    printf("Grade B");
else
    printf("Grade C");
// Output: Grade B

5. switch statement

Used for multiple choices on a single variable.

switch (choice) {
    case 1: printf("Addition"); break;
    case 2: printf("Subtraction"); break;
    default: printf("Invalid choice");
}
// Output: Subtraction

7. Describe the structure of a C program with an example.

A C program follows a well-defined structure:

Documentation Section: Contains comments (e.g., // Program to add two numbers).
Preprocessor Section: Includes header files (e.g., #include <stdio.h>).
Global Declaration Section: Declares global variables and function prototypes (e.g., int x;, void display();).

main() Function Section: Execution starts here. Contains declarations and statements.

int main() {
    int a, b, sum;
    printf("Enter two numbers: ");
    scanf("%d %d", &a, &b);
    sum = a + b;
    printf("Sum = %d", sum);
    return 0;
}

Subprograms (Functions): User-defined functions written outside main().
```
void display() {
    printf("This is a function.");
}
```

Full Example Program:

#include <stdio.h> // Preprocessor section

// Global Declaration
int globalvar = 10;
void display();

int main() { // main function section
    int a, b, sum; // Declarations
    printf("Enter two numbers: ");
    scanf("%d %d", &a, &b);
    sum = a + b;
    // Statement
    printf("Sum = %d\n", sum);
    display(); // Function call
    return 0;
}

// Subprogram
void display() {
    printf("This is a user-defined function.\n");
}

8. Explain about the various Decision making and branching statement with example.

Decision-making statements alter the flow of program execution based on conditions, allowing the program to "decide" which code to run.

1. if statement

Executes a block if the condition is true.

Syntax: if (condition) { ... } Example:

int x = 10;
if (x > 0) {
    printf("x is positive");
}
// Output: x is positive

2. if-else statement

Executes one block if true, another if false.

Syntax: if (condition) { ... } else { ... } Example:

int x = 5;
if (x % 2 == 0) {
    printf("Even");
} else {
    printf("Odd");
}
// Output: Odd

3. Nested if statement

An if statement inside another if.

if (x > 0) {
    if (x < 10) {
        printf("x is between 1 and 9");
    }
}
// Output: x is between 1 and 9

4. if-else-if ladder

Used to check multiple conditions sequentially.

int marks = 80;
if (marks >= 90)
    printf("Grade A");
else if (marks >= 75)
    printf("Grade B");
else
    printf("Grade C");
// Output: Grade B

5. switch statement

Used for multiple choices on a single variable.

switch (choice) {
    case 1: printf("Addition"); break;
    case 2: printf("Subtraction"); break;
    default: printf("Invalid choice");
}
// Output: Subtraction

Part B: 13-Mark Questions

1. Write a C program to find the sum of two numbers using a flowchart and algorithm.

2. Elaborate the decision making and looping statements with suitable examples.

3. i. Explain the general structure of a C program with an example. ii. Write a C program to find the largest of three numbers using ternary operator.

4. Explain the different types of loops in C with syntax.

5. Explain the all-looping statement with example.

6. Explain the decision-making statement with an example.

7. Describe the structure of a C program with an example.

8. Explain about the various Decision making and branching statement with example.

3. i. Explain the general structure of a C program with an example.
ii. Write a C program to find the largest of three numbers using ternary operator.