The output portion of the do/while loop below (i.e. MENU) outputs twice once youve selected your choice, and I have no idea why its doing this.

#include<iostream>
using namespace std;
struct StudentRecord
{	int stuId;
	char name[20];
	char grade[4];
};
void showOneRecord(StudentRecord);//display a student record
void showRecords(StudentRecord[],int);//display all student records
void bubbleSort(StudentRecord[],int);//sort student records by student id in ascending order
int binarySearch(StudentRecord[],int,int);//search a student record by binary search
int sequentialSearch(StudentRecord[],int,int);//search a student record by sequential search
int main()
{	int const SIZE=6;
	StudentRecord stu[SIZE]={{231,"Avalrez, Luis","B\n"},{567,"Dreian, Arlen","C\n"},{145,"Tol, Norith","A\n"},{786,"Garcia, Steven","D\n"},{362,"Arenas, Jennifer","B\n"},{421,"Solis, Ernesto","A\n"}};
	char choice;//stores only one character
	do
	{	cout<<"---------------MENU---------------"<<endl;
		cout<<"a. Search student by sequential search."<<endl;
		cout<<"b. Search student by biary search."<<endl;
		cout<<"c. Display student records."<<endl;
		cout<<"d. Exit."<<endl;
		cout<<"Enter your choice (a, b, c or d): ";
		choice=cin.get();
		switch(choice)
		{	case'a':
				cout<<"\nEnter student ID number: "<<endl;
				cout<<"\nStudent information: "<<endl;
				break;
			case'b':
				cout<<"\nEnter student ID number: "<<endl;
				cout<<"\nStudent information: "<<endl;
				break;
			case'c':
				cout<<"\nStudent Records:\n"<<endl;
				showRecords(stu,SIZE);
				break;
		}
	}while(choice!='d');
	system ("PAUSE");
	return 0;
}
void showRecords(StudentRecord stu[], int SIZE)
{	for(int i=0;i<SIZE;i++)
	{	cout<<stu[i].stuId<<endl;
		cout<<stu[i].name<<endl;
		cout<<stu[i].grade<<endl;
	}
}

I suspect a '\n' newline character is being left in the input buffer when the user presses the ENTER key. Try using cin.ignore() right after line #24 to force the leftover newline character to be disregarded by your program.

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