File Handling fprintf error - c

Question

I got an assignment about file handling its all about creating bank accounts then it tells you to input you account number,name,pin,and initial balance. My program does work but it prints wrong on the file. What should I do?
Program:
#include<stdio.h>
#include<conio.h>
#include<windows.h>
#include<ctype.h>
struct accacc
{
char accno[5];
char accna[50];
int accpin[4];
int accba;
};
main()
{
FILE *fp;
struct accacc acc;
char ch;
char t[5];
fp=fopen("Accounts.txt","a");
printf("ENTER ACCOUNT NUMBER:\t");
gets(acc.accno);
printf("ENTER ACCOUNT NAME:\t");
scanf("\n");
gets(acc.accna);
printf("ENTER ACCOUNT PIN:\t");
scanf("%d",&acc.accpin);
printf("ENTER INITIAL BALANCE:\t");
scanf("%d",&acc.accba);
printf("CREATE ANOTHER ONE?:\t");
scanf(" %c",&ch);
fprintf(fp,"%s\t%s\t%d\t%d",acc.accno,acc.accna,acc.accpin,acc.accba);
if(toupper(ch)=='Y')
{
do
{
system("cls");
printf("ENTER ACCOUNT NUMBER:\t");
scanf("\n");
gets(t);
if(strcmp(acc.accno,t)==0)
{
printf("ACCOUNT ALREADY EXISTS!");
}
else
{
printf("ENTER ACCOUNT NAME:\t");
scanf("\n");
gets(acc.accna);
printf("ENTER ACCOUNT PIN:\t");
scanf("%d",&acc.accpin);
printf("ENTER INITIAL BALANCE:\t");
scanf("%d",&acc.accba);
printf("CREATE ANOTHER ONE?:\t");
scanf(" %c",&ch );
fprintf(fp,"%s\t%s\t%d\t\t%d\t\n",t,acc.accna,acc.accpin,acc.accba);
}
}while(toupper(ch)=='Y');
}
else
{
fclose(fp);
}
getch();
}

Answer 1

You passed acc.accpin, which is converted to int* for function parameter to %d in fprintf(), which calls for int, so you invoked undefined behavior.
Fixing other issues, your code may be like this:
#include<stdio.h>
#include<stdlib.h> /* add this to use system() */
#include<string.h> /* add this to use strcmp() */
#include<ctype.h>
struct accacc{
char accno[5];
char accna[50];
int accpin; /* change type from int[4] to int */
int accba;
};
char* safer_gets(char* outbuf, size_t max){
size_t idx = 0;
int input;
if(max == 0) return NULL;
while(idx + 1 < max && (input = getchar()) != EOF && input != '\n'){
outbuf[idx++] = input;
}
if (idx == 0 && input == EOF) return NULL;
outbuf[idx] = '\0';
return outbuf;
}
int main(void){
FILE *fp;
struct accacc acc;
char ch;
char t[5];
fp=fopen("Accounts.txt","a");
if(fp == NULL){ /* add error check */
perror("fopen");
return 1;
}
/* stop using gets() and add error check for input */
printf("ENTER ACCOUNT NUMBER:\t");
if(safer_gets(acc.accno,sizeof(acc.accno)) == NULL){
fputs("input error\n", stderr);
return 1;
}
printf("ENTER ACCOUNT NAME:\t");
scanf("\n");
if(safer_gets(acc.accna,sizeof(acc.accna)) == NULL){
fputs("input error\n", stderr);
return 1;
}
printf("ENTER ACCOUNT PIN:\t");
if(scanf("%d",&acc.accpin) != 1){
fputs("input error\n", stderr);
return 1;
}
printf("ENTER INITIAL BALANCE:\t");
if(scanf("%d",&acc.accba) != 1){
fputs("input error\n", stderr);
return 1;
}
printf("CREATE ANOTHER ONE?:\t");
if(scanf(" %c",&ch) != 1){
fputs("input error\n", stderr);
return 1;
}
fprintf(fp,"%s\t%s\t%d\t%d",acc.accno,acc.accna,acc.accpin,acc.accba);
if(toupper(ch)=='Y'){
do{
system("cls");
printf("ENTER ACCOUNT NUMBER:\t");
scanf("\n");
safer_gets(t,sizeof(t));
if(strcmp(acc.accno,t)==0){
printf("ACCOUNT ALREADY EXISTS!");
}
else {
printf("ENTER ACCOUNT NAME:\t");
scanf("\n");
if(safer_gets(acc.accna,sizeof(acc.accna)) == NULL){
fputs("input error\n", stderr);
return 1;
}
printf("ENTER ACCOUNT PIN:\t");
if(scanf("%d",&acc.accpin) != 1){
fputs("input error\n", stderr);
return 1;
}
printf("ENTER INITIAL BALANCE:\t");
if(scanf("%d",&acc.accba) != 1){
fputs("input error\n", stderr);
return 1;
}
printf("CREATE ANOTHER ONE?:\t");
if(scanf(" %c",&ch ) != 1){
fputs("input error\n", stderr);
return 1;
}
fprintf(fp,"%s\t%s\t%d\t\t%d\t\n",t,acc.accna,acc.accpin,acc.accba);
}
}while(toupper(ch)=='Y');
fclose(fp); /* add fclose() here */
}
else{
fclose(fp);
}
}
Note that the "check for duplicate account number" in this code won't work.