文件写入时写不进去文本里面

#include<stdio.h>
#include<process.h>
struct students{
int num;
int score;
char ch[20];
}stu[3]={{1,85,"cr"},{2,95,"cyc"},{3,90,"cqq"}};
int main(){
FILE *fp;
fp=fopen("C:\Users\richard\Desktop\a.txt","w");
if(fp==NULL){
printf("This file con not find!");
exit(0);}
for(int i=0;i<=2;i++)
fprintf(fp,"%d,%d,%s",stu[i].num,stu[i].score,stu[i].ch[20]);
fclose(fp);
return 0;
}
提问
我这个将这个结构体放入文本中是哪里出了问题

fprintf(fp,"%d,%d,%s",stu[i].num,stu[i].score,stu[i].ch[20]);这一行把[20]去掉
("C:\Users\richard\Desktop\a.txt","w")变成("C:\\Users\\richard\\Desktop\\a.txt","w")