C language to write a simple address book, say simple 1 function is simple, 2 is also not add read and write file operation, just as a linked list operation of an exercise, hope to give the novice 1 this guidance and help.

Code:

/*  Please note the source          */
/*  By Urahara (ID:blueboy82006)      */
/* http://blog.csdn.net/blueboy82006     */
#include <stdio.h>
#include <stdlib.h>
#include<string.h>
#include<ctype.h>
typedef struct node{
 char name[12];
 char phone[13];
 struct node *next;
}LNode;
LNode *h;        // The first node
static int flag=1;     // Address book creation tag
int CreateNode(void)     // Create a single circular linked list
{
 if(flag)
 {
  LNode *p;
  h=(LNode *)malloc(sizeof(LNode));
  h->next=NULL;
  p=h;
  flag--;
  return 1;
 }
 else
  return 0;
}
int InsertNode(void)    // Insert the function
{
 if(!flag)
 {
  LNode *t;
  char name1[12];
  char phone1[13];
  printf("/n Enter name: ");
  scanf("%s",name1);
  printf("/n Enter contact number: ");
  scanf("%s",phone1);
  t=(LNode *)malloc(sizeof(LNode));
  strcpy(t->name,name1);
  strcpy(t->phone,phone1);
  t->next=h->next;
  h->next=t;
  return 1;
 }
 else
  return 0;
}
int SearchNode(void)    // Query function
{
 if(!flag)
 {
  LNode *p;
  int x=0;
  char name1[12];
  printf("/n Input query name: ");
  scanf("%s",name1);
  p=h;
  printf("/n Query results: ");
  while(p->next)
  {
   p=p->next;
   if(strcmp(p->name,name1)==0)
   {
    printf("/n Name: %s/n Contact Number: %s/n",p->name,p->phone);
    x++;
   }
  }
  if(!x)
   printf("/n No information found! ");
  return 1;
 }else
  return 0;
}
int DeletNode(void)    // Delete function
{
 if(!flag)
 {
  LNode *pre,*p;
  char name1[12];
  p=h;
  printf("/n Enter the name of the contact to delete: ");
  scanf("%s",name1);
  while(p->next)
  {
   pre=p;
   p=p->next;
   if(strcmp(p->name,name1)==0)
   {
    pre->next=p->next;
    free(p);
    printf(" Delete successful! /n");
    break;
   }
  }
  if(!p->next)
   printf("/n No information to delete found! ");
  return 1;
 }
 else
  return 0;
}
int PrintNode(void)    // Output function
{
 if(!flag)
 {
  LNode *p;
  p=h;
  while(p->next)
  {
   p=p->next;
   printf("/n Name: %s /t Contact Number: %s",p->name,p->phone);
  }
  return 1;
 }
 else
  return 0;
}
int main()       // The main function
{
 char n;
 printf("/n/n");
 printf("/t/t    The address book /t/n");
 printf("/t/t| -- -- -- -- -- -- -- -- |/n");
 printf("/t/t|        |/n");
 printf("/t/t| [1]  Create an address book      |/n");
 printf("/t/t| [2]  Insert the name of the contact    |/n");
 printf("/t/t| [3]  Find the name of the contact    |/n");
 printf("/t/t| [4]  Delete the name of the contact    |/n");
 printf("/t/t| [5]  Output all contact information    |/n");
 printf("/t/t| [0]  exit       |/n");
 printf("/t/t|        |/n");
 printf("/t/t|  If you have not created a new table, please do so first!   |/n");
 printf("/t/t|        |/n");
 printf("/t/t| -- -- -- -- -- -- -- -- |/n");
 printf("/n");
 printf(" Please enter your options (0-5):");
 while(1)
 {
  scanf("%s",&n);
  while(!(n=='0'||n=='1'||n=='2'||n=='3'||n=='4'||n=='5'))
  {
   printf(" Please enter your options (0-5):");
   scanf("%s",&n);
  }
  system("CLS");
  switch(n)
  {
  case '0':{
   printf("/n/t/t Thank you for your use! /n");
   return 0;
     }
  case '1':{
   if(CreateNode())
    printf(" Address book set up successfully! /n");
   else
    printf(" The address book has been set up, no need to repeat! /n");
   break;
     }
  case '2':{
   if(InsertNode())
    printf(" Added successfully! /n");
   else
    printf(" Add failed, please create address book first! /n");
   break;
     }
  case '3':{
   if(SearchNode())
    printf("/n");
   else
    printf(" Search failed, please create address book first! /n");
   break;
     }
  case '4':{
   if(DeletNode())
    printf("/n");
   else
    printf(" Delete failed, please create address book first! /n");
   break;
     }
  case '5':{
   if(PrintNode())
    printf("/n Above is all contact information ./n");
   else
    printf("ERROR , please create the address book first! /n");

   break;
     }
  default:{printf(" Input does not meet the requirements! ");}
  }
  printf("/n/n");
  printf("/t/t    The address book /t/n");
  printf("/t/t| -- -- -- -- -- -- -- -- |/n");
  printf("/t/t|        |/n");
  printf("/t/t| [1]  Create an address book      |/n");
  printf("/t/t| [2]  Insert the name of the contact    |/n");
  printf("/t/t| [3]  Find the name of the contact    |/n");
  printf("/t/t| [4]  Delete the name of the contact    |/n");
  printf("/t/t| [5]  Output all contact information    |/n");
  printf("/t/t| [0]  exit       |/n");
  printf("/t/t|        |/n");
  printf("/t/t|  If you have not created a new table, please do so first!   |/n");
  printf("/t/t|        |/n");
  printf("/t/t| -- -- -- -- -- -- -- -- |/n");
  printf("/n");
 }
}