#include<stdio.h>
#include<conio.h>
#define maxN 2048

long countLines(FILE* inFile)
{
	long count = 0; char line[maxN];
	while(fgets(line, maxN - 1, inFile) != NULL)
	{
		count++;
	}
	return count;
}
void main()
{
	FILE* fp = fopen("Data.txt", "rt");
	if(fp != NULL)
	{
		long cnt = countLines(fp);
		printf("\nSo dong trong van ban = %d\n", cnt);
	}
	getch();
}

Line 17: error: conio.h: No such file or directory
In function 'main':
Line 15: warning: return type of 'main' is not 'int'