scanf is skipped even if using fflush - c

Question

I have a scanf that doesn't accept input. The value is automatically zero, even if the variable wasn't initialized. The scanf is skipped:
printf("\nEnter the number of the student to be dropped: ");
fflush(stdin);
scanf(" %d ",&choice);
printf("choice is %d", choice);
When the program is run, it immediately displays "choice is 0".
The snippet above is taken from the drop() function in this code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct student{
char name[50];
char* course;
};
main()
{
char repeat;
do{
system("cls");
int mainchoice;
printf("Student Enrollment System");
printf("\n");
printf("\n");
printf("1. View\n");
printf("2. Enroll\n");
printf("3. Drop enrollment\n");
printf("Select choice: ");
fflush(stdin);
scanf("%d",&mainchoice);
system("cls");
switch(mainchoice){
case 1:
view();
break;
case 2:
enroll();
break;
case 3:
drop();
break;
default:
printf("Please enter a valid number.");
getch();
fflush(stdin);
break;
}
printf("\nWould you like to make another transaction? [Y/N]: ");
fflush(stdin);
scanf("%c",&repeat);
}while(repeat=='Y'||repeat=='y');
}
view(){
int ctr = count();
printf("Enrolled Students:\n\n");
system("type records.txt");
printf("\n\nNumber of students enrolled: %d", ctr);
getch();
fflush(stdin);
}
enroll(){
int choice;
char validate;
printf("1. Information Technology\n");
printf("2. Computer Science\n");
printf("3. Computer Engineering\n");
printf("4. Information Systems\n");
struct student news;
printf("Name: ");
fflush(stdin);
gets(news.name);
printf("Course Number: ");
fflush(stdin);
scanf("%d", &choice);
switch(choice){
case 1:
news.course = "BSIT";
break;
case 2:
news.course= "BSCS";
break;
case 3:
news.course = "BSCpE";
break;
case 4:
news.course = "BSIS";
break;
default:
printf("Please enter a valid number\n");
break;
}
printf("Enroll %s to %s? [Y/N]:",news.name,news.course);
fflush(stdin);
scanf("%c", &choice);
if(choice=='Y' || choice=='y')
{
FILE * records;
records = fopen("records.txt", "a+");
fprintf(records, "%s, %s\n",news.name,news.course);
fclose(records);
printf("%s has been enrolled to %s\n",news.name, news.course);
}
else
{
printf("You have chosen to cancel your transaction");
}
}
drop(){
printf("Drop Student:\n\n");
int ctr = 0;
int choice; //which student to delete
char c;
FILE * record; // original records.txt
FILE* repo; //temporary data storage
record = freopen("records.txt", "r", stdin);
while((c = fgetchar())!=EOF){
if(c == '\n'){
}
else{
ctr=ctr+1;
printf("%d. ", ctr);
while(1){
printf("%c",c);
c= fgetchar();
if(c=='\n'){
printf("%c",c);
break;
}
}
}
}
fclose(record);
fflush(stdin);
fflush(stdin);
printf("\nEnter the number of the student to be dropped: ");
fflush(stdin);
scanf(" %d ",&choice);
getch();
getch();
fflush(stdin);
ctr = 1;
fflush(stdin);
repo = fopen("temp.txt","w");
record = freopen("records.txt","r",stdin);
while((c = getchar()) != EOF){
if(c == '\n'){
}
else{
while(ctr!=choice){
fprintf(repo,"%c",c);
c= fgetchar();
if(c=='\n'){
fprintf(repo,"%c",c);
ctr = ctr + 1;
break;
}
}
}
}
fclose(record);
fclose(repo);
getch();
}
//counts the number of rows in the record
int count(){
int ctr=0;
char c;
FILE * records;
records = freopen("records.txt","r", stdin);
if(records!=NULL){
while((c=fgetchar()) !=EOF){
if(c=='\n'){
ctr = ctr+1;
}
}
}
fclose(records);
return ctr;
}
Doing fflush doesn't seem to help. Any ideas?

Answer 1

The behavior of fflush is not defined for input streams; fflush(stdin) is a coding error, and you should remove those calls from your code.
When scanning for individual characters, add a blank space before the %c conversion specifier; this will tell scanf to skip any leading whitespace and read the next non-whitespace character:
scanf(" %c", &choice);
The %d and %s conversion specifiers will skip over any leading whitespace.
Edit
Implicit typing is no longer supported as of C99, and it's a bad habit to get into. Explicitly type your functions, and use void as the parameter list to specify that they take no arguments:
main() => int main(void)
view() => void view(void) // void since it isn't returning a value
drop() => void drop(void)
etc.
Similarly, gets was deprecated in C99 and is gone completely as of the 2011 standard. Using it will introduce a point of failure / major security hole in your program. Use fgets instead.