c语言文件操作：将文件text1和文件text2中的相加并存入文件text3中

#include
#include
#include 
int main()
{
    FILE *fp;
    FILE *pf;
    FILE *af;
    char ch1;
    char ch2;
    char ch3;
    int sum;

    if((fp=fopen("text1.text","rt")) == NULL)
    {
   	 	printf("nCannot open file1 strike any key exit!");
   	    getchar();
 	    exit(1);
	}

	if((pf = fopen("text2.text","rt")) == NULL) 
    {
		printf("Cannot open file2，strike any key exit!");
		getchar();
		exit(1);
	}

    if((af = fopen("text3.text","wt")) == NULL) 
    {
		printf("Cannot open file3，strike any key exit!");
		getchar();
		exit(1);
	}

    while (1)  
    {  
        ch1 = fgetc(fp);  

        if (ch1 == EOF)  
        {  
            break;  
        }  

        ch2 = fgetc(pf);  

        if (ch2 == EOF)  
        {  
            break;  
        }  

        if (ch1 >= '0' && ch1 <= '9')       
        {  
            sum = ch1 - '0' + ch2 - '0';  
            ch3 = sum + '0';
            fputc(ch3,af);  
        }  
        else
        {
            fputc(ch2,af);  
        }
    }


	printf("n");
    fclose(fp);
	fclose(pf);
    fclose(af);


}