Read and display a student structure

LAB B08 · 01

Understand the task.

Aim: Read and display a student structure.

Review the related theory in Unit 3.

LAB B08 · 02

Know what goes in and what comes out.

Three lines: a roll number from 1 to 999; a nonempty name of at most 60 characters; and marks from 0 to 100, including a decimal part if needed.

7
Ananya Rao
85.5

Roll = 7
Name = Ananya Rao
Marks = 85.50

Source programs read the documented input directly, without prompt text, so the same sample works in the embedded compiler’s STDIN field.

LAB B08 · 03

Plan the steps before writing code.

1. Define struct Student with roll, name and marks members.
2. Declare one struct Student object.
3. Read and validate student.roll, then consume the rest of that input line.
4. Read the name with fgets, remove its newline and validate its length.
5. Read and validate student.marks.
6. Display the record using the dot member-access operator.

LAB B08 · 04

One complete program. Ready to run.

#include <stdio.h>
#include <string.h>
struct Student {
    int roll;
    char name[62];
    double marks;
};
int main(void)
{
    struct Student student;
    int ch;
    if (scanf("%d", &student.roll) != 1 || student.roll < 1 || student.roll > 999) {
        puts("Enter a roll number from 1 to 999."); return 1;
    }
    while ((ch = getchar()) != '\n' && ch != EOF) { }
    if (fgets(student.name, sizeof student.name, stdin) == NULL) {
        puts("Enter a student name."); return 1;
    }
    student.name[strcspn(student.name, "\n")] = '\0';
    if (strlen(student.name) == 0 || strlen(student.name) > 60) {
        puts("Use a nonempty name of at most 60 characters."); return 1;
    }
    if (scanf("%lf", &student.marks) != 1 || !(student.marks >= 0.0 && student.marks <= 100.0)) {
        puts("Enter marks from 0 to 100."); return 1;
    }
    printf("Roll = %d\nName = %s\nMarks = %.2f\n", student.roll, student.name, student.marks);
    return 0;
}

gcc B08-student-structure.c -o program

LAB B08 · 05

Connect each statement to its purpose.

• struct Student defines the record type; struct Student student declares an object of that type.
• The dot operator accesses a member of the object: student.roll, student.name and student.marks.
• scanf needs the address of numeric members. The name array already converts to a pointer for fgets.
• Consuming the roll-number line prevents its leftover newline from becoming an unintended empty name.
• A bounded fgets read preserves spaces in a name and allows validating the length.
• The example reads one record. An array of structures extends this approach to several students.

LAB B08 · 06

Follow the sample calculation.

LAB B08 · 07

Check more than one input.

Time and storage

O(L) name processing for name length L; one fixed-size record plus constant working space.

Start with the sample, then test a boundary and a case that changes the result. A correct sample alone does not establish that every input is handled correctly.

LAB B08 · 08

Use the real C compiler.

Choose an example and load it into the embedded C compiler. Select I/O inside the compiler, check the sample STDIN, and press Run. Change the input or edit the source to explore a different case.

7
Ananya Rao
85.5

Roll = 7
Name = Ananya Rao
Marks = 85.50

#include <stdio.h>
#include <string.h>
struct Student {
    int roll;
    char name[62];
    double marks;
};
int main(void)
{
    struct Student student;
    int ch;
    if (scanf("%d", &student.roll) != 1 || student.roll < 1 || student.roll > 999) {
        puts("Enter a roll number from 1 to 999."); return 1;
    }
    while ((ch = getchar()) != '\n' && ch != EOF) { }
    if (fgets(student.name, sizeof student.name, stdin) == NULL) {
        puts("Enter a student name."); return 1;
    }
    student.name[strcspn(student.name, "\n")] = '\0';
    if (strlen(student.name) == 0 || strlen(student.name) > 60) {
        puts("Use a nonempty name of at most 60 characters."); return 1;
    }
    if (scanf("%lf", &student.marks) != 1 || !(student.marks >= 0.0 && student.marks <= 100.0)) {
        puts("Enter marks from 0 to 100."); return 1;
    }
    printf("Roll = %d\nName = %s\nMarks = %.2f\n", student.roll, student.name, student.marks);
    return 0;
}

LAB B08 · 09

Explain why the program works.

LAB B08 · 10

Build the next skill.

Read the viva answers, try the extra cases, and return to the lab index to mark this exercise as practised.