sri ramanuja seva

Anna University exam prep
CS 3251 – Programming in C
Past years Questions and Answers – Part 4. (See Part 3 here: 2 marks Q-A on Unit 1. )
Here, 16 marks Q-A on struct (Unit 4) from Nov/Dec 2022. Pls see the images below.

CS3251 – Programming in C
16 Marks – Nov / Dec 2022, Unit 4, topic – structures in C

Question

What is a structure? Create a structure with data members of various types and declare two structure variables. Write a program to read data into these and print the same. Justify the need for structured data type.

Answer

A struct is a user-defined data type in C.
It groups together variables of different data types under a single name.

#include <stdio.h>
// Student data struct
struct Student
{
    int rollNum;      // Stores roll number
    char name[20];    // Stores student name
    char grade;       // Stores grade
};
int main()
{
    struct Student s1, s2;      // Two variables of type struct Student
    // Reading data into the struct variables
    // Details of 1st student
    printf("Enter details for 1st student:\n");
    printf("Enter roll number: ");
    scanf("%d", &s1.rollNum);
    printf("Enter name: ");
    scanf("%s", s1.name);
    printf("Enter grade: ");
    scanf(" %c", &s1.grade);
    // Details of 2nd student
    printf("Enter details for 2nd student:\n");
    printf("Enter roll number: ");
    scanf("%d", &s2.rollNum);
    printf("Enter name: ");
    scanf("%s", s2.name);
    printf("Enter grade: ");
    scanf(" %c", &s2.grade);
    // Displaying the data from the struct variables
    printf("\nStudent 1 details: \n");
    printf("Roll number: %d\n", s1.rollNum);
    printf("Name: %s\n", s1.name);
    printf("Grade: %c\n", s1.grade);
    
    printf("\nStudent 2 details: \n");
    
    printf("Roll number: %d\n", s2.rollNum);
    printf("Name: %s\n", s2.name);
    printf("Grade: %c\n", s2.grade);
    
    // End of program
    return 0;
}

output: 
Student 1 details:
Roll number: 12
Name: Suresh
Grade: A
Student 2 details:
Roll number: 23
Name: Ganesh
Grade: B

Need for Structured Data Type

• Groups related data together under a single name. (Student’s name, roll number, and grade can be stored in a single variable.)
• Represents real-world entities (which contain attributes of different types). Examples: student, employee, book, etc.
• Makes programs organized and makes records easier to handle.

Tip:
Note the blank space before %c in the scanf() statement for reading the grade:
scanf(” %c”, &s1.grade);

The blank space before %c is necessary. Otherwise, we will get erratic behaviour.
Why so?

• There is another scanf() statement before this one to read a string (name).
• A newline character (\n) gets entered for the string scanf() call.
• Then there is another scanf() call for reading the grade. If we don’t put a blank space before %c in the scanf() call, the newline character (\n) left in the input buffer will be read instead of the actual grade.

Part 5 of this series on Anna Univ Q-A is here: Loops in C, Unit 1, 16 marks, Nov/Dec 2022.