#include <malloc.h>

#define MAX_STUDENTS 30

typedef struct
{
	int id;
	/* more fields here */
} Student;

Student *studentDb[MAX_STUDENTS] = { 0 };

Student *AddStudent(int id /* more params here */)
{
	size_t index = 0;
	for (; index < MAX_STUDENTS && studentDb[index]; index++)
		;

	studentDb[index] = malloc(sizeof(Student));
	studentDb[index]->id = id;

	return studentDb[index];
}

Student *DeleteStudent(int id)
{
	for (size_t index = 0; index < MAX_STUDENTS; index++)
	{
		if (studentDb[index] && (studentDb[index]->id == id))
		{
			free(studentDb[index]);
			studentDb[index] = NULL;
		}
	}

	return NULL;
}

Student *GetStudent(int id)
{
	for (size_t index = 0; index < MAX_STUDENTS; index++)
	{
		if (studentDb[index] && (studentDb[index]->id == id))
		{
			return studentDb[index];
		}
	}

	return NULL;
}

void CleanStudentDb()
{
	for (size_t index = 0; index < MAX_STUDENTS; index++)
	{
		if (studentDb[index])
		{
			free(studentDb[index]);
			studentDb[index] = NULL;
		}
	}
}