C++ Double Linked List

#include <cstdio>
#include <cstdlib>
#include <cstring>
#define null ((void *)0)

typedef long long LL;
typedef struct _model {
    char NIM[11];
    char name[200];
    char gender;
    LL income;
    struct _model *next;
    struct _model *prev;
} Model;

Model *head = null;
Model *tail = null;
Model *current = null;

Model* create_new(const char NIM[11], const char name[200], const char& gender, const LL income) {
    Model *temp = (Model*)malloc(sizeof(Model));
    memcpy(temp->name, name, (strlen(name) + 1) * sizeof(char));
    temp->gender = gender;
    temp->income = income;
    temp->next = temp->prev = null;

    return temp;
}

void push_head() {
    current->next = head;
    head->prev = current;
    head = current;
    head->prev = null;
}
void push_tail() {
    tail->next = current;
    current->prev = tail;
    tail = current;
    tail->next = null;
}
void add(const char NIM[11], const char name[200], const char& gender, const LL income) {
    current = create_new(name, gender, income);
    if(head == null) {
        head = tail = current;
    } else if(head == tail) {
        if(income > head->income) {
            push_head();
        } else {
            push_tail();
        }
    } else {
        Model *temp = head;
        while(temp != null) {
            if(income <= temp->income) {
                temp = temp->next;
            } else {
                break;
            }
        }
        if(temp == head) {
            push_head();
        } else if(temp == null) {
            push_tail();
        } else {
            Model *before = temp->prev;
            before->next = current;
            current->prev = before;
            current->next = temp;
            temp->prev = current;
        }
    }
}

void main_menu() {

}
int main() {
    return 0;
}