diff --git a/Workbook/a.out b/Workbook/a.out
index 034e547..93f88f0 100755
Binary files a/Workbook/a.out and b/Workbook/a.out differ
diff --git a/Workbook/test.c b/Workbook/test.c
index 03ff66b..9be4067 100644
--- a/Workbook/test.c
+++ b/Workbook/test.c
@@ -1,13 +1,242 @@
+#include <errno.h>
+#include <stdbool.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 
-int main() {
-    int a = 5;
-    int b = 5;
-    int c = a++;
-    int d = ++b;
-    printf("A: %d\n", a);
-    printf("B: %d\n", b);
-    printf("C: %d\n", c);
-    printf("D: %d\n", d);
+#define ERRORRETURN 10787253
+#define ARRSIZE 4096
+#define EXITVAL 15326
+#define ENOCUSTOMER 692137
+#define ENOPRODUCT 691337
+
+struct Product {
+    int id;
+    char* name;
+    double price;
+    int amount;
+};
+
+struct Customer {
+    char* name;
+    int id;
+};
+
+int find_first_free_customer(struct Customer* array[]) {
+    for (int i = 0; i < ARRSIZE; i++) {
+        if (array[i] == NULL) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+int find_first_free_product(struct Product* array[]) {
+    for (int i = 0; i < ARRSIZE; i++) {
+        if (array[i] == NULL) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+int find_product_index(int id, struct Product* array[]) {
+    for (int i = 0; i < ARRSIZE; i++) {
+        if (array[i] != NULL && array[i]->id == id) {
+            return i;
+        }
+    }
+    errno = ENOPRODUCT;
+    printf("Mit der eingegeben Produktnummer konnte kein Produkt gefunden werden.\n");
+    return ERRORRETURN;
+}
+
+int find_customer_index(int id, struct Customer* array[]) {
+    for (int i = 0; i < ARRSIZE; i++) {
+        if (array[i] != NULL && array[i]->id == id) {
+            return i;
+        }
+    }
+    errno = ENOCUSTOMER;
+    printf("Mit der eingegeben Kundennummer konnte kein Kunde gefunden werden.\n");
+    return ERRORRETURN;
+}
+
+int add_product(struct Product* products[]) {
+    int id, amount;
+    char name[100];
+    double price;
+
+    printf("**********************\n");
+    printf("* WWS Produkteingabe *\n");
+    printf("**********************\n");
+    printf("Bitte geben Sie eine Produktnummer ein: ");
+    scanf("%d", &id);
+    printf("Bitte geben Sie einen Produktnamen ein: ");
+    scanf("%99s", name);
+    printf("Bitte geben Sie einen Preis für das Produkt ein: ");
+    scanf("%lf", &price);
+    printf("Bitte geben Sie die aktuelle Anzahl im Inventar: ");
+    scanf("%d", &amount);
+
+    struct Product* new_product = (struct Product*)malloc(sizeof(struct Product));
+    if (!new_product) {
+        printf("Fehler beim Speicher zuweisen.");
+        errno = ENOMEM;
+        return ERRORRETURN;
+    }
+
+    new_product->id = id;
+    new_product->name = strdup(name); // Duplicate string to avoid issues.
+    new_product->price = price;
+    new_product->amount = amount;
+
+    int index = find_first_free_product(products);
+    if (index == -1) {
+        free(new_product);
+        printf("Kein freier Platz für Produkte.");
+        errno = ENOMEM;
+        return ERRORRETURN;
+    }
+
+    products[index] = new_product;
     return 0;
 }
+
+int add_customer(struct Customer* customers[]) {
+    int id;
+    char name[100];
+
+    printf("*********************\n");
+    printf("* WWS Kundeneingabe *\n");
+    printf("*********************\n");
+    printf("Bitte geben Sie eine Kundennummer ein: ");
+    scanf("%d", &id);
+    printf("Bitte geben Sie einen Kundennamen ein: ");
+    scanf("%99s", name);
+
+    struct Customer* new_customer = (struct Customer*)malloc(sizeof(struct Customer));
+    if (!new_customer) {
+        printf("Fehler beim Speicher zuweisen.");
+        errno = ENOMEM;
+        return ERRORRETURN;
+    }
+
+    new_customer->id = id;
+    new_customer->name = strdup(name); // Duplicate string to avoid issues.
+
+    int index = find_first_free_customer(customers);
+    if (index == -1) {
+        free(new_customer);
+        printf("Kein freier Platz für Kunden.");
+        errno = ENOMEM;
+        return ERRORRETURN;
+    }
+
+    customers[index] = new_customer;
+    return 0;
+}
+
+int print_product(struct Product* products[]) {
+    int id;
+
+    printf("**********************\n");
+    printf("* WWS Produktausgabe *\n");
+    printf("**********************\n");
+    printf("Bitte geben Sie die gesuchte Produktnummer ein: ");
+    scanf("%d", &id);
+
+    int index = find_product_index(id, products);
+    if (index == ERRORRETURN) {
+        return ERRORRETURN;
+    }
+
+    struct Product* product = products[index];
+    printf("======================\n");
+    printf("Produktnummer: %d\n", product->id);
+    printf("Name: %s\n", product->name);
+    printf("Einzelpreis: %.2lf\n", product->price);
+    printf("Anzahl: %d\n", product->amount);
+    printf("Gesamtpreis: %.2lf\n", product->price * product->amount);
+
+    return 0;
+}
+
+int print_customer(struct Customer* customers[]) {
+    int id;
+
+    printf("*********************\n");
+    printf("* WWS Kundenausgabe *\n");
+    printf("*********************\n");
+    printf("Bitte geben Sie die gesuchte Kundennummer ein: ");
+    scanf("%d", &id);
+
+    int index = find_customer_index(id, customers);
+    if (index == ERRORRETURN) {
+        return ERRORRETURN;
+    }
+
+    struct Customer* customer = customers[index];
+    printf("=====================\n");
+    printf("Kundennummer: %d\n", customer->id);
+    printf("Name: %s\n", customer->name);
+
+    return 0;
+}
+
+int menu(struct Customer* customers[], struct Product* products[]) {
+    int input;
+
+    printf("**********************\n");
+    printf("* TH Warenwirtschaft *\n");
+    printf("**********************\n");
+    printf("Optionen:\n");
+    printf("1. Produkteingabe\n");
+    printf("2. Kundeneingabe\n");
+    printf("3. Produktausgabe\n");
+    printf("4. Kundenausgabe\n");
+    printf("5. Verlassen\n");
+    printf("Eingabe: ");
+    scanf("%d", &input);
+
+    errno = 0;
+
+    switch (input) {
+        case 1:
+            add_product(products);
+            if (errno != 0) {return ERRORRETURN;}
+            break;
+        case 2:
+            add_customer(customers);
+            if (errno != 0) {return ERRORRETURN;}
+            break;
+        case 3:
+            print_product(products);
+            if (errno != 0) {return ERRORRETURN;}
+            break;
+        case 4:
+            print_customer(customers);
+            if (errno != 0) {return ERRORRETURN;}
+            break;
+        case 5:
+            return EXITVAL;
+        default:
+            printf("Ungültige Eingabe. Bitte erneut versuchen.\n");
+            break;
+    }
+
+    return 0;
+}
+
+int main() {
+    errno = 0;
+    int menuval = 0;
+    struct Customer* customers[ARRSIZE] = {NULL};
+    struct Product* products[ARRSIZE] = {NULL};
+
+    while (menuval == 0) {
+        menuval = menu(customers, products);
+    }
+
+    return errno;
+}