程序代码：

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



int main(){


    FILE *fp6;
    char str[20];
    int age,i;
    float sum;
    if ((fp6=fopen("datafile.txt","w"))=NULL){
        printf("File can't be opened !");
        exit(1);
    }
    printf("type str:");
    for (i=0;i<19;i++)
        scanf("%c",&str[i]);

    printf("type age,sum:");
    scanf("%d%f",&age,&sum);
    while (strlen(str)>1){
        fprintf(fp6,"%s%d%f",str,age,sum);
        printf("type str,age,sum");
        scanf("%s%d%f",str,&age,&sum);
    }
    fclose(fp6);


    return 0;
}