C++ Inventory Management Project

Intermediate•2 days•classes, file handling, reports

Track stock levels, flag low items, and value the whole warehouse.

What you will build

A stock-control system for a small shop: products come in, sales take them out, and the system warns before anything runs dry. The valuable skills are stock invariants (never below zero), low-stock reporting, and valuing inventory from price × quantity.

What you will learn

Encapsulating stock rules inside a class
Restock and sale transactions with validation
Generating low-stock and valuation reports
Persisting structured records

Feature checklist

Add products: SKU, name, price, quantity
Record sales (refuses overselling)
Record restock deliveries
Low-stock alert list (below threshold)
Total inventory value report
Search products by name or SKU

Starter code

#include <iostream>
#include <map>
#include <string>

struct Product { std::string name; double price; int qty; int reorderAt; };

class Inventory {
    std::map<std::string, Product> stock_;   // key: SKU
public:
    void add(const std::string& sku, Product p) { stock_[sku] = std::move(p); }

    bool sell(const std::string& sku, int n) {
        auto it = stock_.find(sku);
        if (it == stock_.end() || n > it->second.qty) return false;
        it->second.qty -= n;
        return true;
    }
    void restock(const std::string& sku, int n) {
        auto it = stock_.find(sku);
        if (it != stock_.end()) it->second.qty += n;
    }
    void report() const {
        double value = 0;
        for (auto& [sku, p] : stock_) {
            value += p.price * p.qty;
            if (p.qty <= p.reorderAt)
                std::cout << "LOW STOCK: " << p.name << " (" << p.qty
                          << " left)\n";
        }
        std::cout << "Total inventory value: $" << value << "\n";
    }
};

Full walkthrough

Step 1: Model Product and let Inventory own the map

struct Product { std::string sku, name; double price; int qty; } and class Inventory holding std::map<std::string, Product> keyed by SKU. SKU is the key because it is unique by definition and never changes, while product names get retyped and misspelled — key choice is identity choice, same lesson as the library's ISBN.

Step 2: add(): new product or restock-by-another-name

If the SKU is new, insert the product. If it already exists, treat add as a delivery: increase qty (and let the price be updated deliberately, not silently). Ambiguity here causes real-world stock chaos, so make the program SAY which of the two things happened.

Step 3: sell() refuses overselling — atomically

sell(sku, n): find the product, check n <= qty, and only then qty -= n. The check and the subtraction are one operation from the caller's perspective. Selling 10 from a stock of 6 must change NOTHING and explain itself ('Only 6 in stock') — a partial sale nobody asked for is worse than a refusal.

bool Inventory::sell(sku, int n) {
    auto it = stock.find(sku);
    if (it == stock.end() || n > it->second.qty) return false;
    it->second.qty -= n;
    return true;
}

Step 4: restock() is sell() with the sign flipped

restock(sku, n) adds n to qty for an existing SKU. Notice the pattern across this catalogue: symmetric operations (issue/return, deposit/withdraw, sell/restock) share validation shape — find, validate, mutate. Writing the second one should feel like déjà vu, and that feeling is pattern recognition growing.

Step 5: Low-stock alerts from a threshold

A named constant LOW = 10 (or a per-product threshold): list every product with qty < LOW, sorted by qty ascending so the most urgent is first. Alerts are a VIEW over the same data — no separate 'alert list' to maintain or let rot.

Step 6: Report the total inventory value

Sum price × qty over the map: money sitting on shelves. Print it with counts of distinct SKUs and total units. This is the report a shop owner actually opens the program for, so it belongs on the main menu, not buried.

Step 7: Search and persist

Search by SKU (map find, exact) or by name substring (scan values, partial — both styles from earlier projects in one feature). Save the map to a file on every change, one product per line, and reload at startup; then test: oversell attempt leaves qty untouched, restock lifts a product off the low-stock list, restart preserves everything.

Common mistakes

Decrementing stock before checking sufficiency, so a refused sale still ate inventory.
Keying the map by product name, then discovering two suppliers' 'USB Cable' are different products with different prices.
Maintaining a separate low-stock list by hand instead of deriving it from qty each time it is viewed.

Compile and run

g++ -std=c++17 -o inventory inventory.cpp

Sample run

$ ./inventory
1) Add  2) Sell  3) Restock  4) Low stock  5) Value report  6) Search  0) Quit
> 2
SKU:
> USB-CAB
Quantity:
> 5
Sold 5 x USB Cable. Remaining: 35
1) Add  2) Sell  3) Restock  4) Low stock  5) Value report  6) Search  0) Quit
> 2
SKU:
> MSE-02
Quantity:
> 9
Refused: only 6 in stock.
> 4
LOW STOCK (below 10):
  MSE-02  Wireless Mouse — 6 left
> 5
Products: 2 SKUs, 41 units
Total inventory value: 79500.00  (USB Cable 1500 x 35 + Mouse 4500 x 6)
> 0

Try it in your browser

No browser demo is included for this project. Build the C++ version below — that is the real program.

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