problem-16

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct {
    int id;
    char name[30];
    float salary;
} Employee;

void addEmployee(FILE *fp) {
    Employee emp;
    printf("Enter Employee ID: ");
    scanf("%d", &emp.id);
    printf("Enter Employee Name: ");
    scanf("%s", emp.name);
    printf("Enter Employee Salary: ");
    scanf("%f", &emp.salary);

    fseek(fp, 0, SEEK_END);
    fwrite(&emp, sizeof(Employee), 1, fp);
}

void displayEmployees(FILE *fp) {
    Employee emp;
    fseek(fp, 0, SEEK_SET);

    while (fread(&emp, sizeof(Employee), 1, fp) == 1) {
        printf("ID: %d, Name: %s, Salary: %.2f\n", emp.id, emp.name, emp.salary);
    }
}

void updateEmployeeSalary(FILE *fp, int id, float newSalary) {
    Employee emp;
    fseek(fp, 0, SEEK_SET);

    while (fread(&emp, sizeof(Employee), 1, fp) == 1) {
        if (emp.id == id) {
            emp.salary = newSalary;
            fseek(fp, -sizeof(Employee), SEEK_CUR);
            fwrite(&emp, sizeof(Employee), 1, fp);
            break;
        }
    }
}

int main() {
    FILE *fp = fopen("employees.dat", "rb+");
    if (fp == NULL) {
        fp = fopen("employees.dat", "wb+");
        if (fp == NULL) {
            perror("Unable to open file");
            return 1;
        }
    }

    int choice;
    do {
        printf("\n1. Add Employee\n2. Display Employees\n3. Update Employee Salary\n4. Exit\nEnter your choice: ");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                addEmployee(fp);
                break;
            case 2:
                displayEmployees(fp);
                break;
            case 3: {
                int id;
                float newSalary;
                printf("Enter Employee ID to update salary: ");
                scanf("%d", &id);
                printf("Enter new Salary: ");
                scanf("%f", &newSalary);
                updateEmployeeSalary(fp, id, newSalary);
                break;
            }
            case 4:
                fclose(fp);
                printf("Exiting...\n");
                break;
            default:
                printf("Invalid choice! Please try again.\n");
        }
    } while (choice != 4);

    return 0;
}