🛒 Grocery Billing System
Mini Project in C

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

#define MAX_PRODUCTS  8
#define MAX_CART      10
#define GST_RATE      0.05f    /* 5% GST                    */
#define DISC_THRESHOLD 500.0f  /* 10% off if bill > Rs 500  */

/* ── PRODUCT — one item on the shop shelf ── */
typedef struct {
    char  name[30];      /* "Basmati Rice 1kg"    */
    char  category[15]; /* "Grains"              */
    float price;          /* price per unit in Rs  */
    int   stock;          /* units available        */
} Product;

/* ── CART ITEM — what customer picks ── */
typedef struct {
    char  name[30];
    float unitPrice;
    int   qty;
    float subtotal;       /* unitPrice * qty       */
} CartItem;

/* ── SHOP INVENTORY — 8 products ── */
Product initShop() {
    /* Returned for illustration — in main we use array directly */
    Product p = {"Basmati Rice 1kg", "Grains", 75.0f, 50};
    return p;
}

int main() {
    /* Full inventory — array of 8 Product structs */
    Product shop[MAX_PRODUCTS] = {
        {"Basmati Rice 1kg",  "Grains",   75.0f,  50},
        {"Toor Dal 500g",     "Pulses",   65.0f,  40},
        {"Sunflower Oil 1L",  "Oils",     140.0f, 30},
        {"Whole Wheat Atta",  "Grains",   55.0f,  60},
        {"Amul Butter 100g",  "Dairy",    52.0f,  25},
        {"Full Cream Milk 1L","Dairy",    68.0f,  35},
        {"Turmeric Powder",   "Spices",   30.0f,  80},
        {"Sugar 1kg",         "Essentials",42.0f, 70}
    };

    printf("sizeof(Product)  = %zu bytes\n", sizeof(Product));
    printf("sizeof(CartItem) = %zu bytes\n", sizeof(CartItem));
    printf("Shop loaded with %d products.\n", MAX_PRODUCTS);
    printf("First product: %s @ Rs %.2f (stock: %d)\n",
           shop[0].name, shop[0].price, shop[0].stock);
    return 0;
}

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

typedef struct{char name[30];char category[15];float price;int stock;}Product;

/* Display all products — const: read-only */
void displayAll(const Product *shop, int n) {
    printf("\n%-3s %-22s %-12s %7s %6s\n",
           "No","Product","Category","Price","Stock");
    printf("%-3s %-22s %-12s %7s %6s\n",
           "---","----------------------","------------","-------","------");

    for (int i = 0; i < n; i++) {
        printf("%-3d %-22s %-12s %7.2f %6d",
               i+1, shop[i].name, shop[i].category,
               shop[i].price, shop[i].stock);
        if (shop[i].stock < 10) printf("  *** LOW");
        printf("\n");
    }
}

/* Display by category — skip non-matching */
void displayByCategory(const Product *shop, int n,
                        const char *cat) {
    printf("\n--- Category: %s ---\n", cat);
    int found = 0;
    for (int i = 0; i < n; i++) {
        if (strcmp(shop[i].category, cat) != 0) continue;
        printf("  %-22s Rs %7.2f  (stock: %d)\n",
               shop[i].name, shop[i].price, shop[i].stock);
        found++;
    }
    if (!found) printf("  No products in this category.\n");
}

int main() {
    Product shop[] = {
        {"Basmati Rice 1kg", "Grains",   75.0f, 50},
        {"Toor Dal 500g",    "Pulses",   65.0f, 40},
        {"Sunflower Oil 1L", "Oils",    140.0f, 7},
        {"Whole Wheat Atta", "Grains",   55.0f, 60},
        {"Amul Butter 100g", "Dairy",    52.0f, 25},
        {"Full Cream Milk 1L","Dairy",   68.0f, 8},
        {"Turmeric Powder",  "Spices",   30.0f, 80},
        {"Sugar 1kg",        "Essentials",42.0f,70}
    };
    displayAll(shop, 8);
    displayByCategory(shop, 8, "Dairy");
    return 0;
}

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

typedef struct{char name[30];char category[15];float price;int stock;}Product;
typedef struct{char name[30];float unitPrice;int qty;float subtotal;}CartItem;

/* Returns 1 on success, 0 on failure
   Modifies shop[idx].stock AND fills cart[*cartCount] */
int addToCart(Product *shop, int shopSize,
               CartItem *cart, int *cartCount,
               int productIdx, int qty) {

    /* Validate index */
    if (productIdx < 0 || productIdx >= shopSize) {
        printf("  Invalid product number.\n");
        return 0;
    }

    Product *p = &shop[productIdx];   /* pointer to chosen product */

    /* Validate stock */
    if (p->stock < qty) {
        printf("  Sorry! Only %d units of %s in stock.\n",
               p->stock, p->name);
        return 0;
    }

    /* Validate cart space */
    if (*cartCount >= 10) {
        printf("  Cart is full (max 10 items).\n");
        return 0;
    }

    /* Fill cart slot via pointer */
    CartItem *slot = &cart[*cartCount];
    strncpy(slot->name, p->name, 29);
    slot->unitPrice = p->price;
    slot->qty       = qty;
    slot->subtotal  = p->price * qty;

    /* Deduct stock from real inventory — non-const pointer */
    p->stock -= qty;

    (*cartCount)++;   /* advance cart counter via pointer */

    printf("  Added: %s x%d = Rs %.2f\n",
           slot->name, qty, slot->subtotal);
    return 1;
}

void showCart(const CartItem *cart, int n) {
    printf("\n--- Cart (%d items) ---\n", n);
    for(int i=0;i<n;i++)
        printf("  %-22s x%-3d Rs %.2f\n",
               cart[i].name, cart[i].qty, cart[i].subtotal);
}

int main() {
    Product shop[] = {
        {"Basmati Rice 1kg", "Grains",  75.0f, 50},
        {"Toor Dal 500g",   "Pulses",  65.0f, 40},
        {"Sunflower Oil 1L","Oils",   140.0f,  3},
        {"Amul Butter 100g","Dairy",   52.0f, 25}
    };
    CartItem cart[10];
    int cartCount = 0;

    printf("=== Customer Shopping ===\n");
    addToCart(shop, 4, cart, &cartCount, 0, 2);  /* Rice x2    */
    addToCart(shop, 4, cart, &cartCount, 1, 1);  /* Dal x1     */
    addToCart(shop, 4, cart, &cartCount, 2, 5);  /* Oil x5 — fail */
    addToCart(shop, 4, cart, &cartCount, 2, 2);  /* Oil x2     */

    showCart(cart, cartCount);

    printf("\nStock after shopping:\n");
    printf("  Rice stock now: %d\n", shop[0].stock);
    printf("  Oil  stock now: %d\n", shop[2].stock);
    return 0;
}

#include <stdio.h>
#include <time.h>

typedef struct{char name[30];float unitPrice;int qty;float subtotal;}CartItem;
#define GST_RATE        0.05f
#define DISC_THRESHOLD  500.0f
#define DISC_RATE       0.10f

/* Compute grand total — returns via output pointers */
float calcTotal(const CartItem *cart, int n,
                float *gstOut, float *discOut) {
    float subtotal = 0;
    for (int i = 0; i < n; i++)
        subtotal += cart[i].subtotal;

    *discOut = (subtotal > DISC_THRESHOLD)
               ? subtotal * DISC_RATE : 0.0f;
    *gstOut  = (subtotal - *discOut) * GST_RATE;

    return subtotal - *discOut + *gstOut;
}

/* Detailed bill — itemised */
void printDetailed(const CartItem *cart, int n,
                    float grand, float gst, float disc) {
    time_t now = time(NULL);
    printf("\n================================================\n");
    printf("           ANANTA GROCERY STORE\n");
    printf("           %s", ctime(&now));
    printf("================================================\n");
    printf("%-22s %5s %10s\n","Item","Qty","Amount");
    printf("------------------------------------------------\n");

    float subtotal = 0;
    for (int i = 0; i < n; i++) {
        printf("%-22s %5d %10.2f\n",
               cart[i].name, cart[i].qty, cart[i].subtotal);
        subtotal += cart[i].subtotal;
    }

    printf("------------------------------------------------\n");
    printf("%-27s %10.2f\n", "Subtotal", subtotal);
    if (disc > 0)
        printf("%-27s %10.2f\n", "Loyalty Discount (10%)", -disc);
    printf("%-27s %10.2f\n", "GST (5%)", gst);
    printf("================================================\n");
    printf("%-27s %10.2f\n", "GRAND TOTAL", grand);
    printf("================================================\n");
    printf("     Thank you for shopping with us!\n");
    printf("================================================\n");
}

/* Compact receipt */
void printCompact(const CartItem *cart, int n,
                   float grand, float gst, float disc) {
    printf("\n[RECEIPT] Items:%d  GST:%.2f  Disc:%.2f  TOTAL: Rs %.2f\n",
           n, gst, disc, grand);
}

int main() {
    CartItem cart[] = {
        {"Basmati Rice 1kg", 75.0f,  3, 225.0f},
        {"Toor Dal 500g",   65.0f,  2, 130.0f},
        {"Sunflower Oil 1L",140.0f, 2, 280.0f},
        {"Sugar 1kg",       42.0f,  1,  42.0f}
    };
    int n = 4;

    float gst, disc;
    float grand = calcTotal(cart, n, &gst, &disc);

    /* Function pointer — swap bill style */
    void (*printBill)(const CartItem*, int,
                      float, float, float) = printDetailed;
    printBill(cart, n, grand, gst, disc);

    printf("\n--- Compact mode ---\n");
    printBill = printCompact;        /* swap — same call */
    printBill(cart, n, grand, gst, disc);
    return 0;
}

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

typedef struct{char name[30];char category[15];float price;int stock;}Product;

/* Search — partial name match via strstr
   Returns pointer to product or NULL */
Product* searchProduct(Product *shop, int n,
                        const char *keyword) {
    printf("\nSearching for \"%s\"...\n", keyword);
    for (int i = 0; i < n; i++) {
        if (strstr(shop[i].name, keyword)) {
            printf("  Found: %s @ Rs %.2f (stock: %d)\n",
                   shop[i].name, shop[i].price, shop[i].stock);
            return &shop[i];   /* pointer into real array */
        }
    }
    printf("  Not found.\n");
    return NULL;
}

/* Restock — non-const pointer, modifies stock */
void restockItem(Product *p, int qty) {
    if (!p) { printf("  No product to restock.\n"); return; }
    p->stock += qty;
    printf("  Restocked: %s. New stock: %d\n",
           p->name, p->stock);
}

/* Low stock report — walk and flag */
int lowStockReport(const Product *shop, int n, int threshold) {
    printf("\n=== LOW STOCK REPORT (below %d units) ===\n", threshold);
    int count = 0;
    for (int i = 0; i < n; i++) {
        if (shop[i].stock < threshold) {
            printf("  %-22s stock: %d  [REORDER]\n",
                   shop[i].name, shop[i].stock);
            count++;
        }
    }
    if (!count) printf("  All products well-stocked.\n");
    return count;
}

/* Update price — modify through pointer */
void updatePrice(Product *p, float newPrice) {
    if (!p) return;
    printf("  Price update: %s  Rs %.2f → Rs %.2f\n",
           p->name, p->price, newPrice);
    p->price = newPrice;
}

int main() {
    Product shop[] = {
        {"Basmati Rice 1kg", "Grains",   75.0f, 4},
        {"Toor Dal 500g",   "Pulses",   65.0f, 40},
        {"Sunflower Oil 1L","Oils",    140.0f, 2},
        {"Amul Butter 100g","Dairy",    52.0f, 7},
        {"Sugar 1kg",       "Essentials",42.0f,70}
    };

    /* Search returns pointer — use it directly */
    Product *found = searchProduct(shop, 5, "Rice");
    restockItem(found, 50);
    updatePrice(found, 79.0f);

    searchProduct(shop, 5, "Oil");

    lowStockReport(shop, 5, 10);
    return 0;
}