Array, variable protoyping, and function in C++

alfangelalfa.cpp

#include <cstdlib>
#include <iostream>

using namespace std;

int mahasiswa [10] = {
	2009140507,
	2009140508,
	1234567890
};

int panjangMahasiswa = sizeof(mahasiswa) / sizeof(*mahasiswa);

int data [3][4] = {
	// {"NIM", "Nilai A", "Nilai B", "Nilai C"}
	{2009140507, 90, 80, 70},
	{2009140508, 70, 80, 90},
	{1234567890, 10, 20, 30}
};

int dataRow = sizeof(data) / sizeof(data[0]);
int dataCol = sizeof(data[0]) / sizeof(*data[0]);

// Prototyping hack ;) [I HATE C++]
void masukkanInput();

void proses(int nim) {
	cout << "NIM kamu: " << nim << endl;
	for (int i = 0; i < dataRow; ++i) {
		for (int j = 0; j < dataCol; ++j) {
			if (nim == data[i][j]) {
				float rataRata = (data[i][1] + data[i][2] +data[i][3]) / 3;
				bool lulus;
				
				if(rataRata > 60) {
					lulus = true;
				} else {
					lulus = false;
				}

				cout << "Nilai A: " << data[i][1] << endl;
				cout << "Nilai B: " << data[i][2] << endl;
				cout << "Nilai C: " << data[i][3] << endl;
				cout << "Nilai Rata-rata: " << rataRata << endl;
				if(lulus) {
					cout << "Selamat! Kamu udah lulus" << endl;
				} else {
					cout << "Emang enak kagak lulus!" << endl;
				}
			}
		}
	}
}

void callback(bool err, int nim) {
	if(err) {
		// NIM tidak terdaftar, masukin NIM lagi
		cout << "Maaf, NIM yang kamu masukkan salah, coba lagi..." << endl;
		masukkanInput();
	} else {
		// NIM terdaftar, go to process
		proses(nim);
	}
}

void daftar(int nim) {
	for (int i = 0; i < panjangMahasiswa; ++i) {
		if (nim == mahasiswa[i]) {
			callback(false, mahasiswa[i]);
			return;
		}
	}
	callback(true, 0);
}

void masukkanInput() {
	int nim;
	cout << "Masukkan NIM: ";
	cin >> nim;
        if(!cin) {
            cout << "Error! NIM bersifat numerik kan?" << endl;
	    return;
        }
	daftar(nim);
}

void selamatDatang() {
	cout << "================================" << endl;
	cout << "        UNIVERSITAS ANU         " << endl;
	cout << "================================" << endl;
}

int main() {
	selamatDatang();
	masukkanInput();
}