第3章运算符与表达式

1、哈尔滨工业大学哈尔滨工业大学计算机科学与技术学院计算机科学与技术学院苏小红苏小红2021-11-122/512021-11-123/512021-11-124/51Example:2021-11-125/512021-11-126/51Example:浮点数除法浮点数除法(Floating Division) or or both are floats整数除法整数除法(Integer Division) and are integers2021-11-127/51Example:2021-11-128/51Example:2021-11-129/512021-11-1210/51Example

2、:1152101remainderresult2021-11-1211/51Example:-115-2-10-1remainderresult2021-11-1212/51Example:11-5-210 1remainderresult2021-11-1213/51Example:2021-11-1214/512021-11-1215/512021-11-1216/51Example: 2021-11-1217/51Example:2021-11-1218/51Example:2021-11-1219/512021-11-1220/512021-11-1221/51关键是如何分离个位、关键

3、是如何分离个位、十位和百十位和百位数字？位数字？2021-11-1222/51#include main() int x = 153, b0, b1, b2, sum; b2 = x / 100; b1 = (x - b2 * 100) / 10; b0 = x % 10; sum = b2 + b1 + b0; printf(b2=%d, b1=%d, b0=%d, sum=%dn, b2, b1, b0, sum);2021-11-1223/512021-11-1224/512021-11-1225/51Example:num = num + 5;num1520Example:num +=

4、 5;2021-11-1226/51已知已知 int a = 3;执行执行 a += a -= a * a 后，变量后，变量a的值？的值？ a += a -= a * a a += a -= 9 a += -6 a = -12执行执行 a += a -= a *= a 后，变量后，变量a的值？的值？ a += a -= a *= a a += a -= 9 a += 0 a = 02021-11-1227/51OperationExamples of expressionDescription+=num += 5;num = num + 5;-=num -= 5;num = num 5;*=n

5、um *= 5;num = num * 5;/=num /= 5;num = num / 5;%=num %= 5;num = num % 5;2021-11-1228/512021-11-1229/512021-11-1230/51Example:j = +i - 2i5similar to j? 462021-11-1231/51Example:j = i+ - 2i5similar to j? 362021-11-1232/51int a=3;printf(%d, -a+);a3similar to 42021-11-1233/512021-11-1234/51circumference

6、 = 33.300854area = 88.247263#include main() double r = 5.3; printf(circumference = %fn, 2*3.14159*r); printf(area = %fn, 3.14159*r*r);2021-11-1235/51#include main() double r; printf(Input r:); scanf(%lf, &r); printf(circumference = %fn, 2*3.14159*r); printf(area = %fn, 3.14159*r*r); Input r: 5.3

7、 circumference = 33.300854 area = 88.247263在程序中直接使用的常数称在程序中直接使用的常数称为幻数为幻数(Magic Number) 2021-11-1236/512021-11-1237/512021-11-1238/51#include main() double r; printf(Input r:); scanf(%lf, &r); printf(circumference = %fn, 2*PI*r); printf(area = %fn, PI*r*r);2021-11-1239/51#include #define PI 3.14

8、159;#define R 5.3;main()printf(area = %fn, PI * R * R);printf(circumference = %fn, 2 * PI * R);相当于执行相当于执行#include main()printf(area = %fn, 3.14159;*5.3;*5.3;);printf(circumference = %fn, 2*3.14159;*5.3;);2021-11-1240/51#include main() const double PI = 3.14159; double r; printf(Input r:); scanf(%lf,

9、 &r); printf(circumference = %fn, 2*PI*r); printf(area = %fn, PI*r*r);2021-11-1241/51doublefloatlongunsignedintchar，short低高2021-11-1242/512021-11-1243/512021-11-1244/51Example: int x = 10;float y;y = (float)x;x10y?10.0000002021-11-1245/51Example: int total, number;float average;average = total / number;total15number2average?7.000000两个整数运算的结果两个整数运算的结果还是整数，不是浮点数还是整数，不是浮点数2021-11-1246/51Example: int total, number;float average;average = (float)total / number;total15number2average?7.5000002021-11-1247