C language design simple phone book

This paper shares the specific code of C language for your reference. The specific content is as follows

#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <stdlib.h>
#include <getch.h>

typedef struct Contact{ // Define the contact structure 
 char name[20]; // The name 
 char sex; // gender 
 char tel[12]; // The phone 
}Contact;

Contact contacts[100];

void show_contact(Contact* conp){ // Display contact information 
 printf(" Name: %s\t Gender: %s\t Telephone: %s\n",conp->name,'w'==conp->sex?" female ":" male ",conp->tel); 
}

void scan_contact(Contact* conp){ // Enter contact information 
 printf(" Please enter your name, gender ( w Female: m : Male), Telephone: ");
 scanf("%s%s%s",conp->name,&conp->sex,conp->tel);
}

void add_contacts(void){ // Add contacts 
 for(int i=0;i<100;i++){
 if(0 == contacts[i].sex){
  scan_contact(contacts+i);
  printf(" Added successfully! \n");
  return;
 }
 } 
 printf(" The addition is full \n");
}

void del_contacts(void){ // Delete contacts 
 char str[20] = {};
 printf(" Please enter the deletion name: \n"); 
 scanf("%s",str);
 for(int i=0;i<100;i++){
 if(0 == strcmp(str,contacts[i].name)){
  contacts[i].sex = 0;
  printf(" Contact deleted successfully \n");
  return;
 } 
 }
 printf(" The contact does not exist \n");
}
void find_contacts(void){ // Find contacts 
 char str[20] = {};
 printf(" Please enter the phone number you want to check \n");
 scanf("%s",str);
 getchar();
 for(int i=0;i<100;i++){
 if(strstr(contacts[i].tel,str)){
  show_contact(contacts+i);
 } 
 }
 printf(" Please enter any key to continue ...\n");
 getch();
}

void list_contacts(void){ // Display contact information 
 for(int i=0;i<100;i++){
 if(contacts[i].sex){
  show_contact(contacts+i);
 } 
 }
 printf(" Please enter any key to continue ...\n");
 getch();
 
}
 
void change_contacts(void){ // Modify contact information 
 char str[20] = {};
 printf(" Please enter the name of the contact to be modified: \n"); 
 scanf("%s",str);
 for(int i=0;i<100;i++){
 if(0 == strcmp(str,contacts[i].name)){
  show_contact(contacts+i);
  scan_contact(contacts+i);
  return; 
 } 
 }
 printf(" No contact to modify was found ");
}
char menu(void){
 system("clear");
 printf(" Welcome to the telephone box \n");
 printf("--------------\n");
 printf("1 , adding contacts  \n");
 printf("2 , delete contacts \n");
 printf("3 , modify contact information \n");
 printf("4 , find contacts \n");
 printf("5 , display all contacts \n");
 printf("--------------\n");
 printf(" Please enter the instruction: ");
 char cmd = getch();
 printf("%c\n",cmd);
 return cmd;
}

int main(){
 while(true){
 switch(menu()){
  case '1':add_contacts(); break; 
  case '2':del_contacts(); break; 
  case '3':change_contacts(); break; 
  case '4':find_contacts(); break; 
  case '5':list_contacts(); break; 
  //case '6':exit(); break;
  default: printf("cmd error!\n");
 }
 } 
}
//------------------------------------ conclusion ------------------------------------------
// Add and delete contacts breach: can be selective return value to achieve the addition and deletion. 
// Find contacts  strstr() Function: 
//strstr(str1,str2)  The function evaluates a string str2 Whether it is str1 The substring. If so, the function returns str2 in str1 The address that first appears in; Otherwise, return NULL . 
// So look for contacts can only make phone calls 1 You can find the contacts in the section. 

// The downside: You can't have a previously saved contact every time you open it. 
// Optimization:   You can save contacts to a file and open the file when the program opens.