A simple examination system based on C language

Is to define a student class , Record the student number , full name , Exam results, etc .
Implemented function ： Entry of examination results , And candidate information entry , Examination results query
Code ：

#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <iostream>
#include <vector>
#include <string.h>
using namespace std;

struct Student
{
    
    int ID;
    char name[20];
    float chinese=0.0;
    float math=0.0;
};

int main()
{
    
    vector<Student> Students;
    while(true)
    {
    
        int n=0;
        printf(" Examination system \n");
        printf("1. Student information entry \n");
        printf("2. Check student grades \n");  // Query by student number 
        printf("3. Chinese examination \n");
        printf("4. Math exam \n");
        scanf("%d",&n);

        if(n==1)
        {
    
            printf(" Please enter the student ID and name in turn , Separate with spaces \n");
            Student stu;
            scanf("%d%s",&stu.ID,&stu.name);
            Students.push_back(stu);
            printf(" Student information entered successfully \n");

        }else if(n==2)
        {
    
            printf(" Please enter the student number to be queried \n");
            int id;
            scanf("%d",&id);
            bool isFind=false;
            for(int i=0;i<Students.size();++i)
            {
    
                if(id==Students[i].ID)
                {
    
                    printf(" Student number :%d, full name :%s, Chinese achievement :%.1f, Math scores :%.1f\n",Students[i].ID,
                           Students[i].name,Students[i].chinese,Students[i].math);
                    isFind=true;
                }
            }
            if(!isFind)
            {
    
                printf(" Students don't exist \n");
            }

        }else if(n==3)
        {
    
            int id;
            printf(" Please enter the student number to be tested \n");
            scanf("%d",&id);
            bool isFind=false;
            for(int i=0;i<Students.size();++i)
            {
    
                if(id==Students[i].ID)
                {
    
                    isFind=true;
                    printf(" Chinese examination , A total of 2 topic , Each question 50 branch \n");
                    printf(" The first question is \n");
                    printf(" Why is Li Bai called ?\n");
                    char ti1[20];
                    char ti1key[20]=" Poetry fairy ";
                    scanf("%s",&ti1);
                    int Source=0;
                    if(strcmp(ti1,ti1key)==0)
                    {
    
                        Source+=50;
                        printf(" Correct answer \n");
                    }else
                    {
    
                        printf(" Wrong answer \n");
                    }
                    printf(" The second question is \n");
                    printf(" Who wrote this poem of Acacia \n");
                    char ti2[20];
                    char ti2key[20]=" Wang wei ";
                    scanf("%s",&ti2);
                    if(strcmp(ti2,ti2key)==0)
                    {
    
                        Source+=50;
                        printf(" Correct answer \n");
                    }else
                    {
    
                        printf(" Wrong answer \n");
                    }
                    printf(" The exam is over \n");
                    printf(" Your Chinese score is %d branch ",Source);
                    Students[i].chinese=Source;
                }
            }
            if(!isFind)
            {
    
                printf(" Students don't exist , Please enter the information before taking the exam \n");
            }

        }else if(n==4)
        {
    
            int id;
            printf(" Please enter the student number to be tested \n");
            scanf("%d",&id);
            bool isFind=false;
            for(int i=0;i<Students.size();++i)
            {
    
                if(id==Students[i].ID)
                {
    
                    isFind=true;
                    printf(" Math exam , A total of 2 topic , Each question 50 branch \n");
                    printf(" The first question is \n");
                    printf(" The length of the rectangle is 10, Wide for 5, Then the area of the rectangle is \n");
                    printf("A 50 B 30\n");
                    char ti1[20];
                    char ti1key[20]="A";
                    char tikey1[20]="a";
                    scanf("%s",&ti1);
                    int Source=0;
                    if(strcmp(ti1,ti1key)==0||strcmp(ti1,tikey1)==0)
                    {
    
                        Source+=50;
                        printf(" Correct answer \n");
                    }else
                    {
    
                        printf(" Wrong answer \n");
                    }
                    printf(" The second question is \n");
                    printf(" The three sides of a triangle are 3,4,5, What is a triangle \n");
                    printf("A  an isosceles triangle  B  Equilateral triangle  C  right triangle \n");
                    char ti2[20];
                    char ti2key[20]="C";
                    char ti2key2[20]="c";
                    scanf("%s",&ti2);
                    if(strcmp(ti2,ti2key)==0||strcmp(ti2,ti2key2)==0)
                    {
    
                        Source+=50;
                        printf(" Correct answer \n");
                    }else
                    {
    
                        printf(" Wrong answer \n");
                    }
                    printf(" The exam is over \n");
                    printf(" Your math score is %d branch ",Source);
                    Students[i].math=Source;
                }
            }
            if(!isFind)
            {
    
                printf(" Students don't exist , Please enter the information before taking the exam \n");
            }

        }
        else
        {
    
            printf(" Wrong operation , Please do it again \n");
        }
    }
}