`luc090.c`¶

Problem Statement

Read employee records (code, name, date, salary), sort them by Date of Joining, and write to a target file.

Metadata¶

Property	Detail
Author	Amit Dutta amitdutta4255@gmail.com
Date	08 Feb 2026
License	MIT License (See the LICENSE file for details)
Difficulty	Advanced (index: 6 / 10)

Concepts¶

Beta Feature

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Array
Pointers
Sorting
Iteration
Recursion

Actions¶

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Source Code¶

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

struct date { int d, m, y; };
struct employee {
    int empcode[6]; // Not used as int array usually, likely int id. Assuming int code.
    char empname[20];
    struct date join_date;
    float salary;
};

// Redefining struct for easier usage assuming empcode is int
struct emp_clean {
    int code;
    char name[20];
    struct date doj;
    float salary;
};

void create_emp_file();
int compare_dates(const void *a, const void *b);

int main()
{
    FILE *fp, *ft;
    struct emp_clean e[50];
    int count = 0, i;

    create_emp_file();

    fp = fopen("employee.dat", "rb");
    if (!fp) return 1;

    while (fread(&e[count], sizeof(struct emp_clean), 1, fp) == 1)
        count++;
    fclose(fp);

    qsort(e, count, sizeof(struct emp_clean), compare_dates);

    ft = fopen("emp_sorted.dat", "wb");
    fwrite(e, sizeof(struct emp_clean), count, ft);
    fclose(ft);

    printf("Sorted records written to 'emp_sorted.dat'.\nDisplaying sorted list:\n");
    for(i=0; i<count; i++)
        printf("%s - %02d/%02d/%04d\n", e[i].name, e[i].doj.d, e[i].doj.m, e[i].doj.y);

    return 0;
}

int compare_dates(const void *a, const void *b)
{
    struct emp_clean *e1 = (struct emp_clean *)a;
    struct emp_clean *e2 = (struct emp_clean *)b;

    if (e1->doj.y != e2->doj.y) return e1->doj.y - e2->doj.y;
    if (e1->doj.m != e2->doj.m) return e1->doj.m - e2->doj.m;
    return e1->doj.d - e2->doj.d;
}

void create_emp_file()
{
    struct emp_clean data[] = {
        {1, "John", {12, 5, 2022}, 5000},
        {2, "Jane", {10, 1, 2020}, 6000}, // Senior
        {3, "Bob",  {15, 8, 2021}, 5500}
    };
    FILE *f = fopen("employee.dat", "wb");
    fwrite(data, sizeof(struct emp_clean), 3, f);
    fclose(f);
}

Explanation¶

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    - Keep explanation clear and short.

    - If something is unclear, say "Not clear from code".

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    FORMAT:

    [START]

    ## What it does

    (Explain the overall purpose in 1-2 sentences)

    ## Step-by-step

    (Explain how the code works in steps, simple language)

    ## Key Concepts

    (List concepts like loop, condition, function, etc.)

    ## Notes

    (Mention any limitations, errors, or assumptions)

    [END]

    CODE (luc090.c):

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

    struct date { int d, m, y; };
    struct employee {
        int empcode[6]; // Not used as int array usually, likely int id. Assuming int code.
        char empname[20];
        struct date join_date;
        float salary;
    };

    // Redefining struct for easier usage assuming empcode is int
    struct emp_clean {
        int code;
        char name[20];
        struct date doj;
        float salary;
    };

    void create_emp_file();
    int compare_dates(const void *a, const void *b);

    int main()
    {
        FILE *fp, *ft;
        struct emp_clean e[50];
        int count = 0, i;

        create_emp_file();

        fp = fopen("employee.dat", "rb");
        if (!fp) return 1;

        while (fread(&e[count], sizeof(struct emp_clean), 1, fp) == 1)
            count++;
        fclose(fp);

        qsort(e, count, sizeof(struct emp_clean), compare_dates);

        ft = fopen("emp_sorted.dat", "wb");
        fwrite(e, sizeof(struct emp_clean), count, ft);
        fclose(ft);

        printf("Sorted records written to 'emp_sorted.dat'.\nDisplaying sorted list:\n");
        for(i=0; i<count; i++)
            printf("%s - %02d/%02d/%04d\n", e[i].name, e[i].doj.d, e[i].doj.m, e[i].doj.y);

        return 0;
    }

    int compare_dates(const void *a, const void *b)
    {
        struct emp_clean *e1 = (struct emp_clean *)a;
        struct emp_clean *e2 = (struct emp_clean *)b;

        if (e1->doj.y != e2->doj.y) return e1->doj.y - e2->doj.y;
        if (e1->doj.m != e2->doj.m) return e1->doj.m - e2->doj.m;
        return e1->doj.d - e2->doj.d;
    }

    void create_emp_file()
    {
        struct emp_clean data[] = {
            {1, "John", {12, 5, 2022}, 5000},
            {2, "Jane", {10, 1, 2020}, 6000}, // Senior
            {3, "Bob",  {15, 8, 2021}, 5500}
        };
        FILE *f = fopen("employee.dat", "wb");
        fwrite(data, sizeof(struct emp_clean), 3, f);
        fclose(f);
    }

luc090.c¶