Set the address book function to database maintenance, and add user name and password

The phenomenon and background of the problem

Change query and sorting to dynamic linked list
In the main menu interface , Enter the address book 、 Delete 、 modify 、 Add functions and merge them into database maintenance functions , When this option is selected , Ask the user to enter the user name and password , If you set the database maintenance personnel 2 people , Can be set in the program accordingly 2 User name and password , Only when it's right , Before entering the next level of maintenance

Problem related code , Do not paste screenshots

#include
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
using namespace std;
typedef struct _TEL_INFO
{
int no;// Number
char name[20];// full name
char tel_num[20];// Phone number
char phone_num[20];// cell-phone number
int code;// Zip code
char add[20];// Address
char rela_ship[20];// Relationship
}TEL,*PTEL;

int menu()
{
int chioce;
system("cls");
printf("1: Enter contact \n");
printf("2: Delete Contact \n");
printf("3: Modify contact \n");
printf("4: Show contacts \n");
printf("5: Query contact \n");
printf("6: Sort phone numbers \n");
printf("0: sign out \n");
printf(" Please enter the selection :");
scanf("%d",&chioce);
while(chioce<0||chioce>6)
{
printf(" Please reselect :");
scanf("%d",&chioce);
}
return chioce;
}

void Print_TEL(PTEL TEL,int n)
{
int i;
for(i=0;i<n;i++)
{
printf("%10d",TEL[i].no);
printf("%10s",TEL[i].name);
printf("%20s",TEL[i].tel_num);
printf("%20s",TEL[i].phone_num);
printf("%10d",TEL[i].code);
printf("%20s",TEL[i].add);
printf("%20s\n",TEL[i].rela_ship);
}
}
int Delete_Tel(PTEL tel,int n)
{
int i,num,j;
char temp[20];
system("cls");
printf(" Please enter the number to delete :");
scanf("%d",&num);

for(i=0;i<n;i++){    if(tel[i].no==num)    {        break;    }}if(i==n){    printf(" No such number information !\n");    system("pause");    return n;}Print_TEL(&tel[i],1);

printf(" confirm deletion ?(Y/N):");
scanf("%s",temp);
if(!strcmp(temp,"Y")||!strcmp(temp,"y"))
{
for(j=i;j<n;j++)
{
tel[j]=tel[j+1];
}
printf(" Delete successful !\n");
system("pause");
return n-1;
}
else
{
printf(" Delete cancelled !\n");
system("pause");
return n;
}
}
int Add_Tel(PTEL tel,int n)
{
int i,flag=0;
system("cls");
printf(" Please enter the contact number :");
scanf("%d",&tel[n].no);
for(i=0;i<n;i++)
{
if(tel[i].no==tel[n].no)
{
flag=1;
break;
}
}
if(flag)
{
printf(" The number already exists !\n");
system("pause");
return n;
}
printf(" Please enter the contact name :");
scanf("%s",tel[n].name);
printf(" Please enter the contact number :");
scanf("%s",tel[n].tel_num);
printf(" Please enter the contact phone :");
scanf("%s",tel[n].phone_num);
printf(" Please enter the contact postal code :");
scanf("%d",&tel[n].code);
printf(" Please enter contact address :");
scanf("%s",tel[n].add);
printf(" Please enter the contact relationship :");
scanf("%s",tel[n].rela_ship);

printf(" Input succeeded !\n");system("pause");return n+1;

}

void Sort_And_Print(PTEL tel,int n)
{
int i,j;
TEL temp;
system("cls");
for(i=0;i<n;i++)
{
for(j=i;j<n;j++)
{
if(strcmp(tel[i].phone_num,tel[j].phone_num)>0)
{
temp = tel[i];
tel[i]=tel[j];
tel[j]=temp;
}
}
}
Print_TEL(tel,n);
system("pause");
}

void Sreach_Tel(PTEL tel,int n)
{
int i,num;
system("cls");
printf(" Please enter the number to query :");
scanf("%d",&num);

for(i=0;i<n;i++){    if(tel[i].no==num)    {        break;    }}if(i==n){    printf(" No such number information !\n");    system("pause");    return ;}Print_TEL(&tel[i],1);system("pause");

}

void Save_File(TEL tel[],int n)
{
int i;
FILE* fp=fopen("tel.txt","w+");
if(fp==NULL)
{
return ;
}
for(i=0;i<n;i++)
{
fwrite(&tel[i],sizeof(TEL),1,fp);
}
fclose(fp);
}

int Open_File(TEL tel[])
{
int i=0;
FILE* fp=fopen("tel.txt","r+");
if(fp==NULL)
{
return 0;
}
while(fread(&tel[i],sizeof(TEL),1,fp))
{
i++;
}
return i;
}

void Modify_Tel_Menu(TEL tel[],int n)
{
int i,num,chioce;
system("cls");
printf(" Please enter the number to be modified :");
scanf("%d",&num);

for(i=0;i<n;i++){    if(tel[i].no==num)    {        break;    }}if(i==n){    printf(" No such number information !\n");    system("pause");    return ;}do{    system("cls");    Print_TEL(&tel[i],1);    printf("1: Change the name \n");    printf("2: Change the phone number \n");    printf("3: Modify your phone \n");    printf("4: Modify zip code \n");    printf("5: Change address \n");    printf("6: Modify the relationship \n");    printf("0: Back to main menu \n");    printf(" Please enter the selection :");    scanf("%d",&chioce);    while(chioce<0||chioce>6)    {        printf(" Please reselect :");        scanf("%d",&chioce);    }    switch(chioce)    {    case 1:        printf(" Please enter a new name :");        scanf("%s",tel[i].name);        printf(" Modification successful !\n");        system("pause");        break;    case 2:        printf(" Please enter a new phone number :");        scanf("%s",tel[i].tel_num);        printf(" Modification successful !\n");        system("pause");        break;    case 3:        printf(" Please enter a new phone :");        scanf("%s",tel[i].phone_num);        printf(" Modification successful !\n");        system("pause");        break;    case 4:        printf(" Please enter a new zip code :");        scanf("%d",&tel[i].code);        printf(" Modification successful !\n");        system("pause");        break;    case 5:        printf(" Please enter a new address :");        scanf("%s",tel[i].add);        printf(" Modification successful !\n");        system("pause");        break;    case 6:        printf(" Please enter a new relationship :");        scanf("%s",tel[i].rela_ship);        printf(" Modification successful !\n");        system("pause");        break;    }}while(chioce!=0);

}

int main(int argc,char* argv[])
{
int chioce;// Record selection
TEL tel[100];// Save employee information
int NUM=0;// Record the number of employees
NUM=Open_File(tel);
system("mode con: cols=120 lines=30");
do
{
chioce=menu();
switch(chioce)
{
case 1:
NUM=Add_Tel(tel,NUM);
Save_File(tel,NUM);
break;
case 2:
NUM=Delete_Tel(tel,NUM);
Save_File(tel,NUM);
break;
case 3:
Modify_Tel_Menu(tel,NUM);
Save_File(tel,NUM);
break;
case 4:
system("cls");
Print_TEL(tel,NUM);
system("pause");
break;
case 5:
Sreach_Tel(tel,NUM);
break;
case 6:
Sort_And_Print(tel,NUM);
break;
}
}while(chioce!=0);

return 0;

}

Operation results and error reporting contents

nothing

My solution ideas and tried methods

Do not know the encryption method of database maintenance function , Password string , Modification of dynamic linked list

What I want to achieve