_Bool類型：布爾變量，其值只有1（真）和0（假）。是C語言中的變量名，C語言中所有的非0數字都被視爲真。
給布爾變量取一個能表示真或假值的變量名是一種常見的做法。
1 /*boolean.c--使用_Bool類型的變量variable*/ 2 #include<stdio.h> 3 int main(void) 4 { 5 long num; 6 long sum=0L; 7 _Bool input_is_good; 8 9 printf("Please enter an integer to be summed "); 10 printf("(q to quit):"); 11 input_is_good=(scanf("%ld",&num)==1); 12 while(input_is_good) 13 { 14 sum=sum+num; 15 printf("Please enter next integer (q to quit):"); 16 input_is_good=(scanf("%ld",&num)==1); 17 } 18 printf("Those integers sum to %ld.\n",sum); 19 20 return 0; 21 }/*程序中把比較的結果賦值給_Bool類型的變量input_is_good 22 /* 23 Sample Output 24 25 Please enter an integer to be summed (q to quit):1 26 Please enter next integer (q to quit):2 27 Please enter next integer (q to quit):3 28 Please enter next integer (q to quit):4 29 Please enter next integer (q to quit):5 30 Please enter next integer (q to quit):6 31 Please enter next integer (q to quit):8 32 Please enter next integer (q to quit):0 33 Please enter next integer (q to quit):w 34 Those integers sum to 29. 35 36 */
