C語言入門①

1.輸出九九乘法表

#include<stdio.h >
int main( ){
	int i = 1,d = 1,cf=0;
	for (i = 1; i<10; i++){
		for (d = 1; d <= i; d++){
			cf = i*d;

			printf("%d*%d=%d\t", i,d,cf);
		}
		printf("\n");
	}
	system ("pause");
	
}

2.判斷素數

#include<stdio.h>
int main( ){
	int i = 100;
	while (i <= 200){
		int d = 2;
		while (d != i - 1){
			
			int r = i%d;
			if (r == 0){
				printf("%d不是素數\n", i);
				break;
			}
			else{
				printf("%d是素數\n",i);
				break;
			}
			d += 1;
		}
		i++;
	}
	system("pause");
}
 

3.判斷閏年

#include<stdio.h>
int main(){
	int year = 1000;
	while (year <= 2000){
		if (year % 400 == 0){

			printf("%d是閏年\n", year);
		}
		else if (year % 4 == 0 && year % 100 != 0){
			printf("%d是閏年\n", year);
		}
		else
		{
			printf("%d不是閏年\n", year);
		}
	year=year+1;
	}
	system("pause");
}