Secured authentication system for an organization

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C

A C program to:
System should check if user is valid
If user is valid it should ask user whether he wants to know account balance, make fund transfer or update balance.
If user is not valid inform admin about unauthorized access.
If more than 3 wrong login attempts for user, then that account has to be locked.
Admin gets monthly reports of unauthorized access.

What I have tried:

Creating structure and some user authentication but didnt worked.
Want to create the project as database based using C. Any ideas on how to store the username and password in a file?

for(i=0;i<row;i++){
			if(strcmp(user.userName,userNames[i]) == 0 ){
				userType=2;
				break;
			}
		}
	}
	if(userType==1||userType==2){
		res = validatePassword(user.password);
	}
	printf("%d",userType);
	printf("\n%d",res);
}
int validatePassword(char passwd[]){
	return 1;
}