手动创建text1，text2,编程创建text3，将text1和text2除了第一行和最后一行，其他行对应数字相加放在text3对应位置

1.按有进位方式来写：

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


//手动创建text1，text2,编程创建text3，将text1和text2除了第一行和最后一行，其他行对应数字相加
//放在text3对应位置

int main(int argc, char **argv)
{  
    FILE *fp1, *fp2, *fp3;  //指向文件的指针变量
    char ch1, ch2, ch3;    
   
    fp1 = fopen("text1.txt", "r+");
    fp2 = fopen("text2.txt", "r+");
    fp3 = fopen("text3.txt", "w+");
    
    int decade;   //十位
    int units;    //个位
    int num;
    int sum;
    char decade_c, units_c;

    while((ch1 = fgetc(fp1)) != EOF  && (ch2 = fgetc(fp2)) != EOF)
    {
        sum = 0;
        if(ch1 <= '9' && ch1 >= '0')
        {
            while(ch1 <= '9' && ch1 >= '0')
            {
                num = ch1 - '0' + ch2 - '0';
                sum = sum * 10 + num;

                ch1 = fgetc(fp1);
                ch2 = fgetc(fp2);
            }

            decade = sum / 10;
            units = sum % 10;

            decade_c = decade + '0';
            units_c = units + '0';

            fputc(decade_c, fp3);
            fputc(units_c, fp3);
        }

        fputc(ch1, fp3);
    }

    fclose(fp1);
    fclose(fp2);
    fclose(fp3);
    return 0;
}

2.按没有进位的方式来写

int main(int argc, char **argv)
{
    FILE *fp1, *fp2, *fp3;  //指向文件的指针变量
    char ch1, ch2, ch3;    

    fp1 = fopen("text1.txt", "r+");
    fp2 = fopen("text2.txt", "r+");
    fp3 = fopen("text3.txt", "w+");

    while((ch1 = fgetc(fp1)) != EOF && (ch2 = fgetc(fp2)) != EOF)
    {
        if(ch1 < '0' || ch1 > '9')
        {
            fputc(ch1, fp3);
        }
        else
        {
            ch1 = ch1 - '0';
            ch2 = ch2 - '0';
            ch3 = ch1 + ch2;
            ch3 = ch3 + '0';

            fputc(ch3, fp3);
        }
    }

    return 0;
}