C assigment

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

void home(char*);
void calculator();
void menu();
void endmessage();

int main() {
    char choice = '0';
    do {
        switch (choice)
        {
        case '0':
            system("cls");
            mainmenu(&choice);
            break;
        case 'A':
            system("cls");
            menu();
            choice = '0';
            break;
        case 'B':
            system("cls");
            calculator();
            choice = '0';
            break;
        case 'C':
            system("cls");
            break;
        default:
            system("cls");
            printf("Invalid option, please choose A, B or C.\n");
            printf("\nWrite 'Back' if you want to get back to the main menu!.\n ");
            scanf(" %c", &choice);
            while (choice != "Back") {
                printf("Invalid option, please choose A, B or C.\n");
                printf("\nWrite 'Back' to go back to the Home Page ");
                scanf(" %c", &choice);
            }
            choice = '0';
        }
    } while (choice != '3');
    system("cls");
    endmessage();
    return 0;
}


void calculator() {
    float a, b;
    char n;
    char choice;
    printf("Calculator:");
    printf("\n");
    printf("\n");
    printf("\nEnter the desired operation: ");
    scanf("%f %c %f", &a, &n, &b);
    if (n == '+')
        printf("\n%.0f+%.0f=%.2f\n", a, b, a + b);

    else if (n == '*')
        printf("\n%.0f*%.0f=%.2f\n", a, b, a * b);

    else if (n == '/')
        if (b == 0)
            printf("MATH ERROR");
        else
            printf("\n%.0f/%.0f=%.2f\n", a, b, a / b);

    while (choice != 'q') {
        printf("\nPlease press 'q' to get back to the main menu: ");
        scanf(" %c", &choice);
    }
}
void menu() {
    char choice;
    printf("Edibles and their Prices::\t");
    printf("\n1-Chips - 5 EGP");
    printf("\n2-Pepsi - 8 EGP");
    printf("\n3-7 UP - 8 EGP");
    printf("\n4-Bubbly - 15 EGP");
    printf("\n5-Milka - 30 EGP");
    printf("\n6-Lays - 25 EGP");
    printf("\n7-Choclate Milkshake - 50 EGP");
    printf("\n8-Sunday - 20 EGP");
    printf("\n9-Happy Meal - 55 EGP");
    printf("\n10-Mountain Dew - 8 EGP");

    while (choice != "Back") {
        printf("\nPlease type 'Back' to go to Home Page.");
        scanf(" %c", &choice);
    }
}

void endmessage() {

    printf("Enjoy!");

}

void home(char* choice) {

    printf("The menu:");
    printf("\n");
    printf("\n");
    printf("Type one of the options, please:\n");
    printf("A - Show Menu.\n");
    printf("B - Calculator.\n");
    printf("C- Exit.\n");
    printf("choose A,B or C:");
    scanf(" %c", &*choice);


}