Student achievement management system (C language)

This code and for reference , Can be used to cope with the school C The language course is set up , Structure array and file are used , There is no linked list , Just a relatively simple version .
If you need to modify or use the source code, take it away by yourself , It's rubbish , You'd better have a look .
There are few notes , For reference only ！

#include <stdio.h>
#include <string.h>
#include <windows.h>
#include <stdlib.h>

typedef struct stuInformation {
    
	char name[20];
	char sex[3];
	char stuId[10];
	int cScore;
}M;
M list[200]={
    0};
int count=0;
void showmenu();										// Show menu bar 
void showHead();										// Show the head of the list 
void showStudentInformtion();							// Show the information of all students 
void searchOneStudent();								// Find the information of a student by student name  
void insertStudentInformation();						// Insert a student's information in the list ( Insert left )
void addInformation();									// Add student information 
void deleteStudentInformation();						// Delete a student's information through the student's name 
void changeStudentInformation();						// Change the information of a student 
void rankScore();										// Sort students according to their grades 
void readFILE();										// Read file data 
void saveFILE();										// Save file data 

void saveFILE() {
    
	FILE *fp;
	int index;
	
	fp = fopen("infor.txt","w+");
	if(fp == NULL) {
    
		printf(" Error opening file ！\n");
		getchar();
		exit(0);
	}
	fwrite(&count,sizeof(int),1,fp);
	fwrite(list,sizeof(M),count,fp);
	fclose(fp);
	return;

}
void readFILE() {
    
	FILE *fp;
	int n=0;
	fp = fopen("infor.txt","a+");
	int index;
	if(fp == NULL) {
    
		printf(" Error opening file ！\n");
		getchar();
		exit(0);
	}
	n=fread(&count,sizeof(int),1,fp);
	if(n==0) {
    
		count=0;
		return;
	}else{
    
	
	fread(list,sizeof(M),count,fp);
   }
	fclose(fp);
	return;
	
}
void showmenu() {
    
	system("cls"); 
	printf("*----------------------------------------------------*\n");
	printf("*  Welcome to use C Language achievement management system  *\n");
	printf("*----------------------------------------------------*\n"); 
	printf("* 1：  entry ( add to ) achievement  *\n");
	printf("* 2：  Delete grades  *\n");
	printf("* 3：  Revise grades  *\n");
	printf("* 4：  Score inquiry  *\n");
	printf("* 5：  Insert grade  *\n");
	printf("* 6：  Score calculation and ranking  *\n");
	printf("* 7：  Show grade information  *\n");
	printf("* 0：  Save the information and exit the system  *\n");
	printf("*----------------------------------------------------*\n");
	printf(" Select operation <0-7> \n");
	return;
}
void showHead() {
    
	printf("%-14s%-14s%-14s%-14s\n"," full name ",
		" Gender ",
		" Student number ",
		"C language achievement " );
	return;
}
void addInformation() {
    
	int index;
	int plus=0;
	readFILE();
	printf(" Please enter the number of students to be entered ：");
	scanf("%d",&plus);

	showHead();
	for(index = count;index < count+plus;index++) {
    
		scanf("%s%s%s%d",list[index].name,list[index].sex,list[index].stuId,&list[index].cScore);
	}
	count=count+plus;
	getchar();
	printf(" Input succeeded ！\n");
	saveFILE();
	printf(" Press any key to continue ！\n");
	getchar();
	showmenu();
	return;
}
void showStudentInformtion() {
    
	int index;
	readFILE();
	printf(" Student information is as follows ：\n");
	showHead();
	for(index = 0;index < count;index++) {
    
		printf("%-14s%-14s%-14s%-14d\n",list[index].name,list[index].sex,list[index].stuId,list[index].cScore);
	}
	getchar();
	saveFILE();
	printf(" Press any key to continue ！\n");
	getchar();
	showmenu();
	return;
}
void searchOneStudent() {
    
	int index;
	int choiceNum;
	int flag = 0;
	char searchName[20];
	char searchStuId[10];
	readFILE();
	printf(" To search by name, please press 1, Please press 2：");
	scanf("%d",&choiceNum);
    switch(choiceNum) {
    
    	case 1:
    	printf(" Please enter the name of the query student ：");
	    scanf("%s",searchName);
	    for(index = 0;index < count;index++) {
    
		    if(strcmp(list[index].name,searchName) == 0) {
    
				flag = 1;
				printf(" The query is successful , The student's information is as follows ：\n");
				showHead();
				printf("%-14s%-14s%-14s%-14d\n",list[index].name,list[index].sex,list[index].stuId,list[index].cScore);
	    	}
    	}
		if(flag == 0) {
    
			printf(" The query fails , The student information does not exist ！\n");
		}
		getchar();
		saveFILE();
		printf(" Press any key to continue ！\n");
		getchar();
		showmenu();
		return;
		case 2:
		printf(" Please enter the student number of the query student ：");
		scanf("%s",searchStuId);
		for(index = 0;index < count;index++) {
    
			if(strcmp(list[index].stuId,searchStuId) == 0) {
    
				flag = 1;
				printf(" The query is successful , The student's information is as follows ：\n");
				showHead();
				printf("%-14s%-14s%-14s%-14d\n",list[index].name,list[index].sex,list[index].stuId,list[index].cScore);
	    	}
    	}
		if(flag == 0) {
    
			printf(" The query fails , The student information does not exist ！\n");
		}
		getchar();
		saveFILE();
		printf(" Press any key to continue ！\n");
		getchar();
		showmenu();
		return;
    }


}
void insertStudentInformation() {
    
	int index;
	int insertNum;
	M insertSTI;
	readFILE();
	printf(" Please enter the information of the student to be inserted ：\n");
	showHead();
	scanf("%s%s%s%d",insertSTI.name,insertSTI.sex,insertSTI.stuId,&insertSTI.cScore);
	printf(" Enter the position to insert ( Insert left )：\n");
	scanf("%d",&insertNum);
	insertNum--;
	for(index = count;index > insertNum;index--) {
    
		list[index] = list[index-1];
	}
	list[insertNum] =insertSTI;
	count++;
	getchar();
	printf(" Insert the success ！\n");
	saveFILE();
	printf(" Press any key to continue ！\n");
	getchar();
	showmenu();
	return;

}

void deleteStudentInformation() {
    
	char deleteName[20];
	int index;
	int flag = 0;
	readFILE();
	printf(" Please enter the name of the student to be deleted ：\n");
	do {
    
		scanf("%s",deleteName);
	    for(index = 0;index < count;index++) {
    
	    	if(strcmp(list[index].name,deleteName) == 0) {
    
				flag = 1;
	    	}
	    }
	    if(flag == 0) {
    
	    	printf(" Input error , Please re-enter ！\n");
	    }
	    if(flag == 1) 
	    	break;
	}while(1);
	for(index;index<count-1;index++) {
    
		list[index] = list[index + 1];
	}
	count--;
	getchar();
	printf(" Delete successful ！\n");
	saveFILE();
	printf(" Press any key to continue ！\n");
	getchar();
	showmenu();
	return;
}
void rankScore() {
    
	int index;
	int i;
	int j;
	M temp;
	readFILE();
	for(i = 0;i < count;i++) {
    
		for(j = 0;j < count - i - 1;j++) {
    
			if(list[j].cScore < list[j + 1].cScore) {
    
				temp = list[j];
				list[j] = list[j + 1];
				list[j + 1] = temp;  
			}
		}
	}
	getchar();
	printf(" Sort success ！\n");
	saveFILE();
	printf(" Press any key to continue ！\n");
	getchar();
	showmenu();
	return;
}
void changeStudentInformation() {
    
	char oldName[20];
	int index;
	M newInfo;
	int flag = 0;
	readFILE();
	printf(" Please enter the name of the student to be modified ：\n");
	do {
    
		scanf("%s",oldName);
	    for(index = 0;index < count;index++) {
    
	    	if(strcmp(list[index].name,oldName) == 0) {
    
				flag = 1;
	    	}
	    }
	    if(flag == 0) {
    
	    	printf(" Input error , Please re-enter ！\n");
	    }
	    if(flag == 1) 
	    	break;
	}while(1);
	printf(" Please enter new student information ：\n");
	showHead();
	scanf("%s%s%s%d",newInfo.name,newInfo.sex,newInfo.stuId,&newInfo.cScore);
	for(index = 0;index < count;index++) {
    
		if(strcmp(list[index].name,oldName) == 0) {
    
			list[index] = newInfo;
		}
	}
	getchar();
	printf(" Modification successful ！\n");
	saveFILE();
	printf(" Press any key to continue ！\n");
	getchar();
	showmenu();
	return;
}

int main() {
    
	showmenu();
	int flag;
	do {
    
	scanf("%d",&flag);
	switch (flag) {
    
		case 1:
		addInformation();
		break;
		case 2:
		deleteStudentInformation();
		break;
		case 3:
		changeStudentInformation();
		break;
		case 4:
		searchOneStudent();
		break;
		case 5:
		insertStudentInformation();
		break;
		case 6:
		rankScore();
		break;
		case 7:
		showStudentInformtion();
		break;
		case 0:
		saveFILE();
		printf(" Saved successfully , Thank you for using. ！\n");
		break;
		default:
		printf(" Input error , Please re-enter ！\n");
	}
}while(flag != 0);

	return 0;
}