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[C language] implementation of three versions of address book small project (including source code)

2022-07-24 09:38:00 【Hua Qiujing】

Catalog
Preface
🧩1. Static version
🧩 demand
🧩 The basic structure
🧩 Initialization function
🧩 Add contact function
🧩 Print function
🧩 Delete contact information
🧩 Find contact information
🧩 Modify contact information
🧩 Sort contact information
🧩 Set clear screen
🧩2. Dynamic version
🧩 New requirements ：
🧩 Change the structure definition
🧩 Change the initialization function
🧩 Change and add contact function
🧩 Destroy address book on exit
🧩3. dynamic + Document version
🧩 explain
🧩 Function to save information
🧩 Check the full capacity function
🧩 Load data from file to memory
🧩4. The source code file
🧩 Please look forward to better works ~

Preface

learned C The basic grammar of language 、 Array 、 function 、 The pointer 、 Custom type 、 Dynamic memory allocation 、 I have mastered some knowledge such as document operation C Basics , At this time, writing small projects is a good way to consolidate , This article will share a wave of use C Language simple implementation of three versions of the address book applet （ The source code is at the end of the article ）.
If you have not mastered the knowledge, you'd better learn it first and then read this article , Welcome readers to my C Language column reference .
Due to the limited level of the author , It's hard to avoid mistakes , Readers can take what they need .

🧩1. Static version

🧩 demand

1. Can be stored in the address book 1000 Personal information

2. Everyone's information includes ： full name + Age + Gender + Telephone + Address

3. Add, delete, check and modify the information of the designated person

4. Can sort the address book information

5. You can print out the required information

6. Quit at any time

🧩 The basic structure

Use three files to realize , One is the file that runs the main function test.c, One is the file that stores the specific functions of the address book contact.c, The other is the corresponding header file contact.h.

Because you need to constantly refresh the status after each operation , So use do while loop .

Initialize the menu , Definition menu function ,1-6 Corresponding to addition, deletion, modification and sorting 、 Print ,0 Exit .

void menu()
{
	printf("************************************************\n");
	printf("*************  1.add      2.del      ***********\n");
	printf("*************  3.search   4.modify   ***********\n");
	printf("*************  5.sort     6.print    ***********\n");
	printf("*************  0.exit                ***********\n");
	printf("************************************************\n");
	printf("************************************************\n");

}

The next operation needs to be determined according to user input , use input Receive input value ,switch() Corresponding 7 In this case .

Defines an enumeration , If you just use case 1: It is not clear which operation corresponds to such statements , And using enumeration constants can be very clear input Which operation does the value of correspond to .

// Prevent forgetting the corresponding operation of options 
enum Option
{
	EXIT,
	ADD,
	DEL,
	SEARCH,
	MODIFY,
	SORT,
	PRINT

};
int main()
{
	int input = 0;
	do
	{
		menu();
		printf(" Please select ：>");
		scanf_s("%d",&input);
		switch (input)
		{
		case EXIT:
			break;
		case ADD:
			break;
		case DEL:
			break;
		case SEARCH:
			break;
		case MODIFY:
			break;
		case PRINT:
			break;
		case SORT:
			break;
		default:
			break;

		}


	} while (input);


	system("pause");
}

To store information about multiple people , And everyone's information has these five attributes , But the corresponding values are different , So use structures to encapsulate variables , Many people use structure array .

Define constants with macros , Easy to modify .

Why use another layer of structure encapsulation ？ To add a variable to record the number of contacts stored in the address book , Be similar to Indexes .

For structure type definitions , Because the two one. c All documents should use the corresponding structure , So put it in the header file contact.h in .

#define MAX_NAME 20
#define MAX_SEX 10
#define MAX_TELE 12
#define MAX_ADDR 30
#define MAX 1000

// Structure type definition -- Personal information 
struct PeoInfo
{
	char name[MAX_NAME];
	char sex[MAX_SEX];
	int age;
	char tele[MAX_TELE];
	char addr[MAX_ADDR];
};

// Address book structure 
typedef struct Contact
{
	struct PeoInfo data[MAX];// Store information 
	int size;// Record the number of valid messages in the current address book 
}Contact;

Then design functions according to functional requirements , Pass the structure address to each function （ More efficient ）.

Each function definition is placed in contact.c, The statement is placed in contact.h.

🧩 Initialization function

Use memset The function initializes the entire structure to 0.

// Initialize address book 
void InitContact(Contact*pc)
{
	// Set all zeros 
	memset(pc, 0, sizeof(pc));
}

🧩 Add contact function

utilize size As index ,size That is, the number of contacts saved at present and the order of the next contacts to be stored , such as size == 5 The representative will now enter the information of the fifth person . Structure array data With size Subscript , After each person's information is added size++.

// Add contacts 
void AddContact(Contact* pc)
{
    // First, judge whether the address book is full 
	if (pc->size == MAX)
	{
		printf(" The address book is full , No more contacts can be added ！\n");
		return;// There is no return value, but it can be used to end the function 
	}
	// Add a person's information 
	printf(" Please enter a name ：>");
	scanf("%s",pc->data[pc->size].name);
	getchar();
	printf(" Please enter age ：>");
	scanf("%d",&(pc->data[pc->size].age));
	printf(" Please enter gender ：>");
	scanf("%s", pc->data[pc->size].sex);
	getchar();
	printf(" Please input the phone number ：>");
	scanf("%s", pc->data[pc->size].tele);
	getchar();
	printf(" Please enter the address ：>");
	scanf("%s", pc->data[pc->size].addr);
	getchar();
	
	pc->size++;// Indexes +1
	printf(" Increase success ！\n");

}

🧩 Print function

In order to see how the information input effect of the previous function is , Let's write the print function first .

// Print contact information 
void PrintContact(const Contact* pc)// Constant pointer anti modification , Only the printing operation does not need to change the original structure 
{
	int i;
	printf("%-15s\t%-5s\t%-5s\t%-12s\t%-20s\n"," full name "," Age "," Gender "," Telephone "," Address ");
	// Print all contact information 
	for (i = 0; i < pc->size; i++)
	{
		printf("%-15s\t%-5d\t%-5s\t%-12s\t%-20s\n", pc->data[i].name, 
												    pc->data[i].age,
													pc->data[i].sex,
													pc->data[i].tele,
													pc->data[i].addr);// In order to look comfortable 
		
	}
}

🧩 Delete contact information

What is the premise of deletion ？ Only the information already exists in the address book can be deleted , So at first, you need to judge whether the address book is empty .

We want to delete the selected contact , You should first find the location of the contact information , Then perform the delete operation .

So we should first write a function to find contacts according to the contact name information . Then pay attention to how to delete contacts , The method adopted here is to make the information of each person behind cover the information of the previous person , Until the last one covers the penultimate personal information , And then size Reduce 1 That is, the total number of storage -1, Originally, the information of the last person was blocked （ The data still exists , If you add contacts, you can overwrite them ）.

// Find contacts （ By name , Used only in this source file ）
static int FindByName(Contact* pc, char name[])
{
	int i = 0;
	for (i = 0; i < pc->size; i++)
	{
		// Using string comparison functions , by 0 Then we find , Returns the corresponding array subscript 
		if (strcmp(pc->data[i].name, name) == 0)
			return i;
	}
	return -1;
}

// Delete Contact 
void DelContact(Contact* pc)
{
	char name[MAX_NAME];
	// First, judge whether the address book is empty 
	if (pc->size == 0)
	{
		printf(" The address book is empty , Cannot delete (*￣3￣)╭");
		return;// End function 
	}
	printf(" Please enter the name of the person to delete ：>");
	scanf("%s", name);
	//1. Find contacts ( By name )
	int pos = FindByName(pc, name);// Returns an array index 
	// Contact not found 
	if (pos == -1)
	{
		printf(" No one is found , Try another one ！\n");
		return;
	}
	//2. Delete Contact 
	int i = 0;
	for (i = pos; i < pc->size - 1; i++)
	{
		// Put the subscript pos The following information moves forward 
		pc->data[i] = pc->data[i + 1];
	}

	// Total number of contacts -1, The original last contact information is equivalent to being blocked 
	pc->size--;
	printf(" Delete successful ！\n");
}

🧩 Find contact information

Find and print the information of the target contact , Here we use FindByName() Functions can be built directly on the basis of functions .

// Find contacts （ According to the name and print the information ）
void SearchContact(Contact* pc)
{
	char name[MAX_NAME];
	printf(" Please enter the name of the contact you want to find ：>");
	scanf("%s",name);
	getchar();
	//1. Find contacts ( By name )
	int pos = FindByName(pc, name);// Returns an array index 
	// Contact not found 
	if (pos == -1)
	{
		printf(" No one is found , Try another one ！\n");
		return;
	}
	else
	{
		//2. Print target contact information 
		printf("%-15s\t%-5s\t%-5s\t%-12s\t%-20s\n", " full name ", " Age ", " Gender ", " Telephone ", " Address ");
		printf("%-15s\t%-5d\t%-5s\t%-12s\t%-20s\n", pc->data[pos].name,
			pc->data[pos].age,
			pc->data[pos].sex,
			pc->data[pos].tele,
			pc->data[pos].addr);
	}
	
}

🧩 Modify contact information

Modification is divided into single modification and all modifications , You need to find the contact person before modifying , You can call FindByName(), If found, print the information of the target first , Then choose single item or modify all , Defined here char modification[5] To receive the user's choice , Reuse strcmp() Compare one by one , When modifying size unchanged , Directly overwrite the original contact information at the specified location .

// Modify contact information 
void ModifyContact(Contact* pc)
{
	char name[MAX_NAME];
	char modification[5];
	printf(" Please enter the name of the contact to be modified ：>");
	scanf("%s", name);
	getchar();

	//1. Find contacts ( By name )
	int pos = FindByName(pc, name);// Returns an array index 
	// Contact not found 
	if (pos == -1)
	{
		printf(" No one is found , Try another one ！\n");
		return;
	}
	else
	{
		//2. Print target contact information 
		printf("%-15s\t%-5s\t%-5s\t%-12s\t%-20s\n", " full name ", " Age ", " Gender ", " Telephone ", " Address ");
		printf("%-15s\t%-5d\t%-5s\t%-12s\t%-20s\n", pc->data[pos].name,
			pc->data[pos].age,
			pc->data[pos].sex,
			pc->data[pos].tele,
			pc->data[pos].addr);

		//3. Modify the information of the target contact 
		printf(" Input Chinese , Individual ( Such as name, etc ) Or all \n");
		printf(" Please enter the option to modify ：>");
		scanf("%s",modification);
		getchar();
		// All modified 
		if (strcmp(modification, " All ") == 0)
		{
			printf(" Please enter a name ：>");
			scanf("%s", pc->data[pos].name);
			getchar();
			printf(" Please enter age ：>");
			scanf("%d", &(pc->data[pos].age));
			printf(" Please enter gender ：>");
			scanf("%s", pc->data[pos].sex);
			getchar();
			printf(" Please input the phone number ：>");
			scanf("%s", pc->data[pos].tele);
			getchar();
			printf(" Please enter the address ：>");
			scanf("%s", pc->data[pos].addr);
			getchar();
		}
		// Single item modification 
		if (strcmp(modification, " full name ") == 0)
		{
			printf(" Please enter a name ：>");
			scanf("%s", pc->data[pos].name);
			getchar();
		}	
		if (strcmp(modification, " Age ") == 0)
		{
			printf(" Please enter age ：>");
			scanf("%d", &(pc->data[pos].age));
		}
		if (strcmp(modification, " Gender ") == 0)
		{
			printf(" Please enter gender ：>");
			scanf("%s", pc->data[pos].sex);
			getchar();
		}
		if (strcmp(modification, " Telephone ") == 0)
		{
			printf(" Please input the phone number ：>");
			scanf("%s", pc->data[pos].tele);
			getchar();

		}
		if (strcmp(modification, " Address ") == 0)
		{
			printf(" Please enter the address ：>");
			scanf("%s", pc->data[pos].addr);
			getchar();
		}
		printf(" Modification successful ！\n");
	}

}

🧩 Sort contact information

After we save the contact information , What if you want to sort the contact information according to some standard ？ have access to qsort function . Here we only sort by name .

static int CmpContactByName(const void* n1, const void* n2)
{
	return strcmp(((PeoInfo *)n1)->name, ((PeoInfo*)n2)->name);
}

void SortContact(Contact* pc)
{
	if (0 == pc->size)
	{
		printf(" The address book is empty , Unable to sort pinch ~\n");
		return;
	}

	qsort(pc->data, pc->size, sizeof(PeoInfo), CmpContactByName);

	printf(" Sort by name ...... Sort success !\n");
}

🧩 Set clear screen

I don't know whether readers will feel uncomfortable reading all the text in the window because of printing all the time , Is there any way to clear the screen after each use （ Refresh the contents of the window ） Well ？

Consider using system commands cls To clear the screen , Need to include header file <stdlib.h>, Use system("cls").

But , If you clear the screen directly , Some printed information can't be seen , Can we do as we want , Only after pressing a certain key can the screen be cleared ？ Tolerable , For example, press the space to clear the screen , use getch（VS Next is _getch） The function receives a character without echo or buffer , At this point, the program will wait for the user to type a value and pause , Enter the corresponding value before continuing , Then you can set a cycle , Only when the received character is a space, it will jump out of the loop to clear the screen , Otherwise, repeat the reception .

    do
	{
		menu();
		printf(" Please select a number ：>");
		scanf("%d",&input);
		switch (input)
		{
		case EXIT:
			printf(" Exit address book ！");
			break;
		case ADD:
			AddContact(&Con);
			break;
		case DEL:
			DelContact(&Con);
			break;
		case SEARCH:
			SearchContact(&Con);
			break;
		case MODIFY:
			ModifyContact(&Con);
			break;
		case PRINT:
			PrintContact(&Con);
			break;
		case SORT:
			SortContact(&Con);
			break;
		default:
			printf(" Wrong choice , Please reselect ！");
			break;

		}

		char ch;
		do
		{
			printf(" Press the space to continue ...\n");
		} while ((ch = _getch()) != ' ');

		system("cls");

	} while (input);

Basically completed the requirements , This is the implementation of the static version of the address book .

🧩2. Dynamic version

🧩 New requirements ：

1. The address book can be stored after initialization 3 Personal information .

2. Whenever the space is full , Automatically add 2 Personal information corresponds to memory space .

🧩 Change the structure definition

stay contact.h in

// Address book structure -- Dynamic version 
typedef struct Contact
{
	struct PeoInfo * data;// Point to the space of dynamic application , Used to store information , It can be directly used as an array 
	int size;// Record the number of valid messages in the current address book 
	int capacity;// Record the maximum capacity of contacts in the current address book                                                                                                                                                                                                                                                                                                                                                
}Contact;

🧩 Change the initialization function

stay contact.h in

#define DEFAULT_SIZE 3// The initial default size of the address book 
#define INC_SIZE 2// Each expansion increment

By the way, rename the name of the structure type

// Structure type definition -- Personal information 
typedef struct PeoInfo
{
	char name[MAX_NAME];
	char sex[MAX_SEX];
	int age;
	char tele[MAX_TELE];
	char addr[MAX_ADDR];
}PeoInfo;

Then change the initialization function , stay contact.c in

// Initialize address book -- Dynamic version 
void InitContact(Contact* pc)
{
	pc->data = (PeoInfo*)malloc(DEFAULT_SIZE*sizeof(PeoInfo));
	// Return value check 
	if (pc->data == NULL)
	{
		perror("InitContact");
		return;
	}
	pc->size = 0;
	pc->capacity = DEFAULT_SIZE;
}

🧩 Change and add contact function

Just think about it , In addition to initialization, is the function to be changed in the dynamic version compared with the previous version only to add the contact function , Only by increasing can it cross the border , It needs to be expanded, right .

stay contact.c in

// Add contacts -- Dynamic version 
void AddContact(Contact* pc)
{
	// First, judge whether the address book is full , Consider increasing capacity 
	if (pc->size == pc->capacity)
	{
		PeoInfo *ptr = (PeoInfo*)realloc(pc->data, (pc->capacity + INC_SIZE) * sizeof(PeoInfo));
		// Return value check 
		if (ptr != NULL)
		{
			pc->data = ptr;
			pc->capacity += INC_SIZE;// Don't forget to update the capacity variable 
			printf(" Contact full , Successful automatic capacity increase ！");
		}

		else
		{
			perror("AddContact");
			printf(" Capacity increase failed !\n");
			return;
		}
			
	}
	// Add a person's information 
	printf(" Please enter a name ：>");
	scanf("%s", pc->data[pc->size].name);
	getchar();
	printf(" Please enter age ：>");
	scanf("%d", &(pc->data[pc->size].age));
	printf(" Please enter gender ：>");
	scanf("%s", pc->data[pc->size].sex);
	getchar();
	printf(" Please input the phone number ：>");
	scanf("%s", pc->data[pc->size].tele);
	getchar();
	printf(" Please enter the address ：>");
	scanf("%s", pc->data[pc->size].addr);
	getchar();

	pc->size++;// Indexes +1
	printf(" Increase success ！\n");

}

🧩 Destroy address book on exit

Because dynamic memory is used , So finally, free the memory , And set the pointer to NULL. Define a function to destroy the address book .

stay contact.c in

// Destroy the address book 
void DestoryContact(Contact* pc)
{
	free(pc->data);
	pc->data = NULL;
}

stay test.c in

Basically completed the requirements , This is the implementation of the dynamic version of the address book .

🧩3. dynamic + Document version

🧩 explain

The previous versions we wrote all store data in memory , The data will be destroyed automatically after the program ends , It's temporary , What if we want to make data persistent ？ You can save it to a file on your hard disk , This requires file operation .

🧩 Function to save information

I'll put the text file here contact Under the project path .

Here we use wb Binary only writes , Because fwrite Function convenience , You can directly output the structure to a file , Anyway, files only store data , You don't need to open it to understand , To view the information, run the program to read the data into the memory to view , So we need to load data from file into memory later .

// Save address book information to a file 
void SaveContact(Contact* pc)
{
	FILE* pf = fopen("contact.txt", "wb");
	// Return value check 
	if (NULL == pf)
	{
		perror("fopen");
		return;
	}

	int i = 0;
	for (i = 0; i < pc->size; i++)
	{
		fwrite(pc->data + i, sizeof(PeoInfo), 1, pf);
	}
	
	fclose(pf);
	pf = NULL;
}

And the data is output to the file before exiting the program .

🧩 Check the full capacity function

When I was writing a dynamic version, I was AddContact The function of checking full capacity and increasing capacity has been written in the function , Now package it as a function to use .

// Check whether it is full , If the capacity is full, it will be automatically increased 
static void CheckCapacity(Contact* pc)
{
	if (pc->size == pc->capacity)
	{
		PeoInfo* ptr = (PeoInfo*)realloc(pc->data, (pc->capacity + INC_SIZE) * sizeof(PeoInfo));
		// Return value check 
		if (ptr != NULL)
		{
			pc->data = ptr;
			pc->capacity += INC_SIZE;// Don't forget to update the capacity variable 
			printf(" Contact full , Successful automatic capacity increase ！ The current capacity is :%d\n", pc->capacity);
		}

		else
		{
			perror("AddContact");
			printf(" Capacity increase failed !\n");
			return;
		}

	}
}

🧩 Load data from file to memory

When to load ？ Of course, it's time to initialize the address book .

Load all the information stored in the file into memory .

To design a LoadContact Function to implement .

// Initialize address book -- dynamic + Document version 
void InitContact(Contact* pc)
{
	pc->data = (PeoInfo*)malloc(DEFAULT_SIZE * sizeof(PeoInfo));
	// Return value check 
	if (pc->data == NULL)
	{
		perror("InitContact");
		return;
	}
	pc->size = 0;
	pc->capacity = DEFAULT_SIZE;

	LoadContact(pc);// Load the existing information in the file 

}

actually , At first, our address book capacity was very limited , At the same time, I don't know how much data there is in the file , Then you can't put all the data into memory , Maybe I can't put it down .

We have to take advantage of the dynamic memory feature , therefore CheckCapacity Functions come in handy .

First read the data in batches PeoInfo Type of temporary variable tmp in , Judge whether the current address book capacity is sufficient , If it is insufficient, it will automatically increase capacity , If enough, it will tmp Put the data in the address book , use pc->size As index （ Similar to AddContact Ideas in functions ）.

Because it needs to be read many times , So let's use a while loop , What is the condition ？fread Function has a return value , Returns the number of successfully read data of the corresponding type , We read one at a time , So take the return value of this function and 1 Compare , be equal to 1 It indicates that a data is currently read , Then continue with the following code , Finally put the data into the address book .

static void LoadContact(Contact* pc)
{
	FILE* pf = fopen("contact.txt", "rb");
	// Return value check 
	if (NULL == pf)
	{
		perror("LoadContact");
		return;
	}

	PeoInfo tmp = {0};

	while (fread(&tmp, sizeof(PeoInfo), 1, pf) == 1)
	{
		CheckCapacity(pc);
		pc->data[pc->size] = tmp;
		pc->size++;
	}

	fclose(pf);
	pf = NULL;

}