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1、1,Chapter 1 Introduction to Computers, Programs, and Java,2,Objectives,To review computer basics, programs, and operating systems (1.2-1.4). To explore the relationship between Java and the World Wide Web (1.5). To distinguish the terms API, IDE, and JDK (1.6). To write a simple Java program (1.7).
2、To display output on the console (1.7). To explain the basic syntax of a Java program (1.7). To create, compile, and run Java programs (1.8). (GUI) To display output using the JOptionPane output dialog boxes (1.9).,3,What is a Computer?,A computer consists of a CPU, memory, hard disk, floppy disk, m
3、onitor, printer, and communication devices.,4,CPU,The central processing unit (CPU) is the brain of a computer. It retrieves instructions from memory and executes them. The CPU speed is measured in megahertz (MHz), with 1 megahertz equaling 1 million pulses per second. The speed of the CPU has been
4、improved continuously. If you buy a PC now, you can get an Intel Pentium 4 Processor at 3 gigahertz (1 gigahertz is 1000 megahertz).,5,Memory,Memory is to store data and program instructions for CPU to execute. A memory unit is an ordered sequence of bytes, each holds eight bits. A program and its d
5、ata must be brought to memory before they can be executed. A memory byte is never empty, but its initial content may be meaningless to your program. The current content of a memory byte is lost whenever new information is placed in it.,6,How Data is Stored?,Data of various kinds, such as numbers, ch
6、aracters, and strings, are encoded as a series of bits (zeros and ones). Computers use zeros and ones because digital devices have two stable states, which are referred to as zero and one by convention. The programmers need not to be concerned about the encoding and decoding of data, which is perfor
7、med automatically by the system based on the encoding scheme. The encoding scheme varies. For example, character J is represented by 01001010 in one byte. A small number such as three can be stored in a single byte. If computer needs to store a large number that cannot fit into a single byte, it use
8、s a number of adjacent bytes. No two data can share or split a same byte. A byte is the minimum storage unit.,7,Storage Devices,Memory is volatile, because information is lost when the power is off. Programs and data are permanently stored on storage devices and are moved to memory when the computer
9、 actually uses them. There are three main types of storage devices:Disk drives (hard disks and floppy disks), CD drives (CD-R and CD-RW), and Tape drives.,8,Output Devices: Monitor,The monitor displays information (text and graphics). The resolution and dot pitch determine the quality of the display
10、.,9,Monitor Resolution and Dot Pitch,The resolution specifies the number of pixels per square inch. Pixels (short for “picture elements”) are tiny dots that form an image on the screen. The resolution can be set manually. The higher the resolution, the sharper and clearer the image is. However, the
11、image may be very small if you set high resolution on a small screen monitor. PC monitors are usually 15-inch, 17-inch, 19-inch, or 21-inch. For a 15-inch monitor, a comfortable resolution setting would be 640480 (307,200 pixels).,resolution,The dot pitch is the amount of space between pixels. The s
12、maller the dot pitch, the better the display.,dot pitch,10,Communication Devices,A regular modem uses a phone line and can transfer data in a speed up to 56,000 bps (bits per second). A DSL (digital subscriber line) also uses a phone line and can transfer data in a speed 20 times faster than a regul
13、ar modem. A cable modem uses the TV cable line maintained by the cable company. A cable modem is as fast as a DSL. Network interface card (NIC) is a device to connect a computer to a local area network (LAN). The LAN is commonly used in business, universities, and government organizations. A typical
14、 type of NIC, called 10BaseT, can transfer data at 10 mbps (million bits per second).,11,Programs,Computer programs, known as software, are instructions to the computer. You tell a computer what to do through programs. Without programs, a computer is an empty machine. Computers do not understand hum
15、an languages, so you need to use computer languages to communicate with them. Programs are written using programming languages.,12,Programming Languages,Machine Language Assembly Language High-Level Language,Machine language is a set of primitive instructions built into every computer. The instructi
16、ons are in the form of binary code, so you have to enter binary codes for various instructions. Program with native machine language is a tedious process. Moreover the programs are highly difficult to read and modify. For example, to add two numbers, you might write an instruction in binary like this: 1101101010011010,13,Programming Languages,Machine Language Assembly Language High-Level Language,Assembly languages were developed to make programming ea
