java 1-1
JavaSE 是 (JavaSE 、JavaEE、JavaME) java基础知识
1.IT的发展历程:
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181047738-200249288.png)
计算机系统 :硬件和软件组成成为计算机
2.操作系统所处环境位置:
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181056707-1849524566.png)
3.计算机进制:二进制,八进制,十进制,十六进制
1)二进制(只能出现0,1 逢二进一):
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181213082-370504360.png)
2)八进制:(只能出现1,2,3,4,5,6,7 逢八进一)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181219363-1649792675.png)
3)十六进制:(只能出现1,2,3,4,5,6,7,8,9,A,B,C,D,E,F 逢十六进一)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181225629-583530881.png)
二进制:0表示低电压 1表示高电压,数字电路
八进制:把一个八个存储空间 组成一个存储单元(第一位表示正负 0代表正,1代表负)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181231800-1298309204.png)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181243316-2090400187.png)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181257769-2003023685.png)
一个字节=8位
1B(byte,字节)=8bit
千位时 1024换算单位 每个单位只差都是1024倍
最终计算机能识别的都是二进制
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181306988-458517612.png)
5.十进制转换二进制:
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181354004-273875517.png)
6.二进制转换为十进制(乘权相加)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181403582-1691775445.png)
八进制的每一位都是三位的二进制
十进制的每一位都是四位的二进制
7.进制转换对照表:
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181413019-404587102.png)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181421441-1095248986.png)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181433082-1002898379.png)
取反码:最高位不变
针对有符号数:(无符号数最高位一定是0)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181457097-326514051.png)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181510222-135994913.png)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181519472-1196957636.png)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181527847-2010874219.png)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181543300-1917899890.png)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181550535-92414963.png)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181634785-758135672.png)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181644238-317243114.png)
![](https://images2015.cnblogs.com/blog/1104343/201702/1104343-20170213181654394-1410751349.png)
8.JAVA SE 基础语法
1){} 代表作用域
2)sys0 +ctal ? (快捷使用输出语句) system.out.println()
例如:向控制台输入文本内容 system.out.println("这是我的第一条编程");
向控制台输入数字内容 system.out.println(33+33);
![](https://images2015.cnblogs.com/blog/1104398/201702/1104398-20170213194529863-1449908184.png)