niit-C# 第二章

1. program often involve decision-making and iterative tasks.You can use conditional constructs for decision making and looping constructs for interative tasks in your programs.
2. Arithmetic assignment operators are used to perform arithmetic operations on two given operands and to assign the resultant value to any of them.
[+=、-=、*=、 /=、%= ]
3. dot operator is used to access the member of a class.

4. If the 'if' and 'else' part of the 'if...else' construct contains single statements,then there is no need to enclose the statements within curly braces.
if 和else 后面只包含一个语句，可以不用大括号
5. The ‘else‘ block in the if...else construct is optional and cam be omitted.
if...else结构的else块是可选的（随意的），可以被忽略。
6. The break statement is used to exit（退出） the switch statement.This prevents the execution of the remaining case structures by ending the execution of the seitch...case construct.
7. Each 'case' keyword is followed by a possible value for the variable.
8. switch...case结构只在开头evaluate an expression，而if...else 结构在每一个if语句后面evaluate the expression.

Activity:
Write a program that accept two primary colors from the user,adds them and displays the output in the new color combination.If the user enters an incorrect color,the program should display the warning。

Loop constructs
9.The while statements always checks the condition before executing the statements within the loop.
while语句总是在循环之前检查条件是不是符合情况（not after！！）
10. The statements within "do...while" loop are executed at least ince,as the statements in the block are executed before the condition is checked.
do...while语句至少执行一次，因为语句在被检查之前就已经执行
11. In the for loop,the initialization expression is executed only once at the beginning of the loop.
只被初始化一次，格式：for(initialization; termination; increment/decrement) {....}
12.break and continue statements
The break statements is used to exit from the loop
The continue statements is used to skip all the subsequent instructions and take the control back to the loop.
[break退出循环，continue跳过后续命令并且让循环继续运行]

Activity：Fibonacci series
in the range 1 to 200 will be : 1,1,2,3,5,8,13...,144.

第二章内容要掌握的就这么多，要把绕的地方再想想，比如自增自减，++i 和i++，break和continue熟练应用、开关语句的注意点，以及与break；配合使用

exercise1： Write a program to identify whether a character entered by a user is a vowel or a consonant.[识别用户输入的字符是元音还是辅音]
exercise2：Write a program to display the highest of any 10 numbers entered.
[显示输入的任何10个数的最高值]
exercise3：Enter a year and determine whether the year is a leap year or not.
(闰年要能被4整除，或能被100整除，或能被400整除)
[ if(year%4==0 || year%100==0 ||year%400==0)
printf("is a leap year");
else printf("is not a leap year."); ]