PPS GTU Paper Solution Winter 2021 | 310003

C language has several types of operators that are used to perform various operations on variables and expressions. These operators can be classified into the following categories:

1. Arithmetic Operators: These operators are used to perform basic mathematical operations such as addition, subtraction, multiplication, and division. For example, +, -, *, / are arithmetic operators.

2. Relational Operators: These operators are used to compare two values and determine the relationship between them. For example, ==, !=, >, <, >=, <= are relational operators.

3. Logical Operators: These operators are used to evaluate logical expressions and return a Boolean value (true or false). For example, &&, ||, ! are logical operators.

4. Assignment Operators: These operators are used to assign a value to a variable. For example, =, +=, -=, *=, /= are assignment operators.

5. Bitwise Operators: These operators are used to perform bit-level operations on variables. For example, &, |, ^, ~, <<, >> are bitwise operators.

6. Miscellaneous Operators: These operators are used for various purposes such as incrementing and decrementing a variable, taking the address of a variable, and dereferencing a pointer. For example, ++, –, &, *, sizeof are miscellaneous operators.

The precedence and associativity order of operators in C language are as follows:

Highest precedence:

postfix increment (++) and decrement (–)

unary plus (+) and minus (-)

bitwise NOT (~)

logical NOT (!)

address-of (&) and indirection (*)

sizeof

type cast

unary conditional operator (?:)

High Precedence:

exponentiation (**)

multiplicative (*, /, %)

additive (+, -)

shift (<<, >>)

relational (<, >, <=, >=, !=, ==)

equality (==, !=)

bitwise AND (&)

bitwise XOR (^)

bitwise OR (|)

logical AND (&&)

logical OR (||)

Low Precedence:

ternary operator (?:)

assignment (=, +=, -=, *=, /=, %=, &=, |=, ^=, <<=, >>=)

the comma (,)

Associativity:

Left-to-right associativity for the assignment operator, ternary operator, and comma operator.

Right-to-left associativity for all other operators.

Both while and do-while loops are used to repeatedly execute a block of code in C programming. However, there are some key differences between the two types of loops:

The while loop: The while loop repeatedly executes a block of code as long as a certain condition is true. The condition is evaluated at the beginning of each iteration before the code inside the loop is executed. If the condition is false, the loop is terminated and the control is transferred to the statement following the loop.

Example:

• int i = 0;
• while (i < 10) {
•     printf(“%d\n”, i);
•     i++;
• }
• In this example, the loop will iterate from 0 to 9 and print the numbers, and it will stop when the condition i < 10 is false.

• The do-while loop: The do-while loop also repeatedly executes a block of code as long as a certain condition is true. However, the condition is evaluated at the end of each iteration, after the code inside the loop is executed. This means that the code inside the loop is always executed at least once, regardless of the initial value of the condition.
• Example:

• int i = 0;
• do {
•     printf(“%d\n”, i);
•     i++;
• } while (i < 10);

• In this example, the loop will also iterate from 0 to 9 and print the numbers, and it will stop when the condition i < 10 is false.

 the main difference between the while loop and the do-while loop is the point at which the condition is evaluated. The while loop evaluates the condition before executing the code inside the loop, while the do-while loop evaluates the condition after executing the code inside the loop

• #include <stdio.h>
• int main() {
•     int i, j;
•     for (i = 1; i <= 3; i++) {
•         for (j = 1; j <= i; j++) {
•             printf(“%d “, i);
•         }
•         printf(“\n”);
•     }
•     return 0;
• }
• The output of the program will be 
• 1
• 2 2
• 3 3 3

• #include <stdio.h>
• int main() {
•     int i, j, k = 1;
•     for (i = 1; i <= 3; i++) {
•         for (j = 1; j <= i; j++) {
•             printf(“%d “, k);
•             k++;
•         }
•         printf(“\n”);
•     }
•     return 0;
• }
• The output of the program will be
• 1
• 2 3
• 4 5 6

1. getch(): It is used to read a single character from the keyboard without waiting for the user to press the enter key. It is defined in the <conio.h> header file. getch() function is used to read a single character from the keyboard, but it does not echo the character to the screen.

2. getchar(): It is used to read a single character from the keyboard, including the enter key. It is defined in the <stdio.h> header file. getchar() function waits for the user to press the enter key after the input.

3. gets(): It is used to read a string (sequence of characters) from the keyboard. It is defined in the <stdio.h> header file. gets() function reads the string entered by the user including whitespace characters and newline characters.

3. puts(): It is used to output a string (sequence of characters) to the screen. It is defined in the <stdio.h> header file. puts() function writes the string to the standard output device and appends a newline character at the end of the string.

• #include <stdio.h>
• // function to perform addition
• double add(double a, double b) {
•     return a + b;
• }
• // function to perform multiplication
• double multiply(double a, double b) {
•     return a * b;
• }
• // function to perform subtraction
• double subtract(double a, double b) {
•     return a – b;
• }
• // function to perform division
• double divide(double a, double b) {
•     return a / b;
• }
• int main() {
•     double a, b;
•     int choice;
•     // menu
•     printf(“Menu:\n”);
•     printf(“1. Addition\n”);
•     printf(“2. Multiplication\n”);
•     printf(“3. Subtraction\n”);
•     printf(“4. Division\n”);
•     printf(“Enter your choice: “);
•     scanf(“%d”, &choice);
•     printf(“Enter two numbers: “);
•     scanf(“%lf %lf”, &a, &b);
•     // perform an operation based on user choice
•     switch(choice) {
•         case 1:
•             printf(“%.2lf + %.2lf = %.2lf\n”, a, b, add(a, b));
•             break;
•         case 2:
•             printf(“%.2lf * %.2lf = %.2lf\n”, a, b, multiply(a, b));
•             break;
•         case 3:
•             printf(“%.2lf – %.2lf = %.2lf\n”, a, b, subtract(a, b));
•             break;
•         case 4:
•             printf(“%.2lf / %.2lf = %.2lf\n”, a, b, divide(a, b));
•             break;
•         default:
•             printf(“Invalid choice\n”);
•     }
•     return 0;
• }

#include <stdio.h>

int check_prime(int num) {

    int i;

    for (i = 2; i <= num / 2; i++) {

        if (num % i == 0) {

            return 0;

        }

    }

    return 1;

}

int main() {

    int num;

    printf("Enter a number: ");

    scanf("%d", &num);

    if (check_prime(num) == 1) {

        printf("%d is a prime number\n", num);

    } else {

        printf("%d is not a prime number\n", num);

    }

    return 0;

}

#include <stdio.h>

int main() {
    int n, i;
    printf("Enter the number of elements in the array: ");
    scanf("%d", &n);

    int arr[n];
    printf("Enter the elements of the array: ");
    for (i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }

    int largest = arr[0];
    for (i = 1; i < n; i++) {
        if (arr[i] > largest) {
            largest = arr[i];
        }
    }
    printf("The largest element in the array is: %d\n", largest);
    return 0;
}

strcat( ): The strcat( ) function is used to concatenate (or append) one string to the end of another string.

strcpy( ): The strcpy( ) function is used to copy one string to another string.

strcmp( ): The strcmp( ) function is used to compare two strings. It compares the ASCII values of each character in the two strings and returns an integer value indicating the result of the comparison. If the first string is lexicographically greater than the second, it returns a positive number, if the first string is lexicographically less than the second, it returns a negative number and if the two strings are equal then it returns 0.

strlen( ): The strlen( ) function is used to find the length of a string. It returns the number of characters in the string, not including the null terminator.

Example:

char str1[20] = "Hello, ";
char str2[] = "world!";
strcat(str1, str2);
printf("%s\n", str1);  // Output: "Hello, world!"
char str3[20];
strcpy(str3, str1);
printf("%s\n", str3);  // Output: "Hello, "
int result = strcmp(str1, str2);
printf("%d\n", result); // Output: -1
int length = strlen(str1);
printf("%d\n", length);  // Output: 7

#include <stdio.h>

int main() {
    int p, q, r;
    printf("Enter the dimensions of matrix A (p x q): ");
    scanf("%d %d", &p, &q);
    printf("Enter the dimensions of matrix B (q x r): ");
    scanf("%d %d", &q, &r);

    int A[p][q], B[q][r], C[p][r];

    // Input matrix A
    printf("Enter the elements of matrix A:\n");
    for (int i = 0; i < p; i++) {
        for (int j = 0; j < q; j++) {
            scanf("%d", &A[i][j]);
        }
    }

    // Input matrix B
    printf("Enter the elements of matrix B:\n");
    for (int i = 0; i < q; i++) {
        for (int j = 0; j < r; j++) {
            scanf("%d", &B[i][j]);
        }
    }

    // Multiply matrices A and B and store result in C
    for (int i = 0; i < p; i++) {
        for (int j = 0; j < r; j++) {
            C[i][j] = 0;
            for (int k = 0; k < q; k++) {
                C[i][j] += A[i][k] * B[k][j];
            }
        }
    }

    // Output matrix C
    printf("The result of multiplying A and B is:\n");
    for (int i = 0; i < p; i++) {
        for (int j = 0; j < r; j++) {
            printf("%d ", C[i][j]);
        }
        printf("\n");
    }

    return 0;
}

A nested if-else ladder is a type of control flow statement in which an “if-else” statement is placed inside another “if-else” statement. This creates a multi-level decision-making structure, where the outcome of one “if-else” statement affects the execution of the next one.

Here is an example of a nested if-else ladder:

int age = 25;
char gender = 'M';

if (age >= 18) {
    if (gender == 'M') {
        printf("You are a male adult.\n");
    }
    else if (gender == 'F') {
        printf("You are a female adult.\n");
    }
    else {
        printf("Invalid gender input.\n");
    }
}
else {
    if (gender == 'M') {
        printf("You are a male minor.\n");
    }
    else if (gender == 'F') {
        printf("You are a female minor.\n");
    }
    else {
        printf("Invalid gender input.\n");
    }
}

#include <stdio.h>

struct student {
    int roll_no;
    int sub1;
    int sub2;
    int sub3;
    int total;
};

int main() {
    struct student s[3];
    int i;

    for (i = 0; i < 3; i++) {
        printf("Enter the roll number of student %d: ", i+1);
        scanf("%d", &s[i].roll_no);
        printf("Enter the marks of 3 subjects for student %d: ", i+1);
        scanf("%d%d%d", &s[i].sub1, &s[i].sub2, &s[i].sub3);
        s[i].total = s[i].sub1 + s[i].sub2 + s[i].sub3; //calculate total marks
    }

    printf("\nRoll No\tSub1\tSub2\tSub3\tTotal\n");
    for (i = 0; i < 3; i++) {
        printf("%d\t%d\t%d\t%d\t%d\n", s[i].roll_no, s[i].sub1, s[i].sub2, s[i].sub3, s[i].total);
    }

    return 0;
}

fopen() is a standard C library function that is used to open a file. It takes two arguments: the name of the file and the mode in which the file should be opened. The return value is a pointer to a FILE structure, which is used to read from or write to the file.

#include <stdio.h>

int main() {
    FILE *fp;

    fp = fopen("example.txt", "r"); // open example.txt in read mode
    if (fp == NULL) {
        printf("Error opening file\n");
        return 1;
    }

    // read from file using fp
    // ...

    fclose(fp); // close the file
    return 0;
}

The available modes for fopen() are:

“r”: Open the file for reading. If the file does not exist or cannot be read, fopen() returns NULL.

“w”: Open the file for writing. If the file does not exist, it will be created. If the file already exists, its contents will be truncated (deleted).

“a”: Open the file for writing in append mode. If the file does not exist, it will be created. If the file already exists, new data will be written to the end of the file.

“r+”: Open the file for reading and writing. The file must exist.

“w+”: Open the file for reading and writing. If the file does not exist, it will be created. If the file already exists, its contents will be truncated (deleted).

“a+”: Open the file for reading and writing in append mode. If the file does not exist, it will be created. If the file already exists, new data will be written to the end of the file.

In C programming, user-defined functions can be broadly categorized into the following types:

• Normal Functions: These are the basic functions that are defined by the user. They perform a specific task and return a value. For example, a function to calculate the area of a circle, a function to find the factorial of a number, etc.

• Recursive Functions: These functions call themselves in order to solve a problem. They are used to solve problems that can be broken down into smaller sub-problems, which are similar to the original problem.

• Function Overloading: In C++, function overloading is possible, which means that multiple functions can have the same name, but different parameter lists. This feature allows for more flexibility and code reusability.

• Inline Functions: These are functions which are expanded in line when they are called, rather than being called through the normal function call mechanism. They are useful for small functions, as they can improve performance by reducing function call overhead.

• Static Functions: These functions have a scope limited to the file in which they are defined. They are not accessible from outside the file, making them useful for implementing hidden functionality that is only used within the file.

• Variadic Functions: These functions can take a variable number of arguments. They are defined using the … notation and are usually used to implement functions that can handle a variable number of arguments like printf, scanf.

• Pointer to Functions: These are functions that take one or more pointer arguments, and/or return a pointer. They are used to pass or return function pointers, which can be used to implement callback functions and other advanced functionality.

Both malloc() and calloc() are C library functions that are used for dynamic memory allocation. They are used to allocate memory on the heap, which can be freed using the free() function.

Here is a comparison of malloc() and calloc():

malloc(): malloc() is used to allocate a block of memory on the heap. The function takes a single argument, which is the size of the memory block to be allocated. The memory block is not initialized and contains garbage values.

int *ptr = (int *) malloc(sizeof(int) * 10);

calloc(): calloc() is used to allocate a block of memory on the heap and initialize it to zero. The function takes two arguments: the number of blocks to be allocated and the size of each block.

int *ptr = (int *) calloc(10, sizeof(int));

• Initialization: malloc() only allocates memory and does not initialize it, whereas calloc() allocates and initializes the memory to zero.

• Arguments: malloc() takes a single argument, the size of the memory block to be allocated, while calloc() takes two arguments, the number of blocks and the size of each block.

• Memory Allocated: malloc() returns a pointer to the first byte of the allocated memory block, whereas calloc() returns a pointer to the first byte of the first block of the allocated memory.

• Performance: calloc() is generally slower than malloc() as it initializes the memory to zero, but is useful when it is necessary to have zero-initialized memory.

#include <stdio.h>

int check_prime(int num) {
    if (num <= 1) {
        return 0;
    }
    for (int i = 2; i < num; i++) {
        if (num % i == 0) {
            return 0;
        }
    }
    return 1;
}

int main() {
    int num;
    printf("Enter a number: ");
    scanf("%d", &num);

    if (check_prime(num)) {
        printf("%d is a prime number.\n", num);
    } else {
        printf("%d is not a prime number.\n", num);
    }

    return 0;
}

The program starts by defining a user-defined function check_prime(), which takes an integer as a parameter. It checks if the number is less than or equal to 1, it returns 0, as it’s not a prime number. Then it uses a for loop to check if the number is divisible by any integer between 2 and itself, if it is divisible, it returns 0, indicating it’s not a prime number. If the number is not divisible by any integer between 2 and itself, the function returns 1, indicating that a number is a prime number.