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Name of Course : Introduction to Java Programming Lecturer: Alexander Shkolnik E- mail: [email protected] Office Hours: Sun 14:00 - 16:00 build 37,room 520 Course number : 202.1.9031 Credits : 4 Course Site : http://www.cs.bgu.ac.il/~ipc161 1 Course Objectives • The main purpose of the course - introduction to Java language programming methods, based on new approaches in computer science. • On the first part of the course students will acquire procedural programming: software development technique that imposes a hierarchical structure on the design of the programs. On the second part of the course students will learn the principles of object-oriented programming (OOP): programming technique based on objects. • Students will learn operation system Windows 7 and Integrated Development Environment (IDE) Eclipse, which provides first – class Java programming tools. • The course includes: algorithm building principles, basic Java commands, control structure, arrays, different kinds of methods (including recursion methods), principles of object-oriented programming (OOP), collections, dynamic data structures and files manipulations. 2 Course requirements : • 1. • 2. • 3. 13 x 3 hours lectures 13 x 2 hours (4 x 2 lab, 9 x 2 frontal) practical lessons 3 programming assignments (about 20 hours each) (every assignment 10 % of the final grade). Submissions: alone only. • 4. Final exam 3 hours long ( 70% of final grade, a "Pass" requirement regarding final exam: 56 ) . No auxiliary material allowed, except for a single two-sided A4 paper sheet (neither printed nor copied). 3 Our course site http://www.cs.bgu.ac.il/~ipc161/Main 4 Review computer basics User Application Programs Operating System Hardware 5 Computer Structure CPU Output Input Internal Memory Monitor Speakers Motors External Memory Hard Disk CD / DVD Tape DiskOnKey Mouse Keyboard Microphone Detectors 6 CPU ( ) מעבד 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 improved continuously. Bus Storage Devices e.g., Disk, CD, and Tape Memory CPU Communication Devices Input Devices Output Devices e.g., Modem, and NIC e.g., Keyboard, Mouse e.g., Monitor, Printer 7 Memory ( ) זיכרון 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 data 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. Bus Storage Devices e.g., Disk, CD, and Tape Memory CPU Communication Devices Input Devices Output Devices e.g., Modem, and NIC e.g., Keyboard, Mouse e.g., Monitor, Printer 8 Memory Unit : Byte • Byte ( )ביתis a unit of digital information. It is an ordered collection of 8 bits ( binary digit), in which each bit denotes the binary value of 1 or 0. • number of bits ( )סיביותused to encode a character of text in the computer, which depended on computer hardware architecture. • A byte can represent 28 = 256 distinct values, such as the integers from 0 to 255. • ASCII (American Standard Code for Information Interchange). 9 How Data is Stored? ● Data of various kinds, such as numbers, characters, 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 performed automatically by the system based on the encoding scheme. ● A byte is the minimum storage unit. Memory address Memory content . . . . . . 2000 01001010 Encoding for character ‘J’ 2001 01100001 Encoding for character ‘a’ 2002 01110110 Encoding for character ‘v’ 2003 01100001 Encoding for character ‘a’ 2004 00000011 Encoding for number 3 1 KB = 1,024 bytes 1 MB = 1,048,576 bytes 1 GB = 1,073,741,824 bytes Storage Devices ( ) התקני אחסון Memory is volatile ( ) נדיף, 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 actually uses them. There are three main types of storage devices: Disk drives, CD drives and Tape drives. Bus Storage Devices e.g., Disk, CD, and Tape Memory CPU Communication Devices Input Devices Output Devices e.g., Modem, and NIC e.g., Keyboard, Mouse e.g., Monitor, Printer 11 USB flash drive ● A USB flash drive is a data storage device that includes flash memory (a special type of memory that can be erased and reprogrammed ) with an integrated Universal Serial Bus (USB) interface. ● USB flash drives are typically removable and rewritable, and physically much smaller than an CD. 12 Operating system ( ) מערכת ההפעלה • An operating system ( OS ) is a software program that enables the computer hardware to communicate and operate with the computer software. • An operating system also has a vital role to play in security. Its job includes preventing unauthorized users from accessing the computer system. • Examples of popular modern operating systems include Microsoft Windows, Android,, Linux, Mac OS X, and IBM z/OS. 13 Operating system, cont. At the simplest level, an operating system does two things: 1. It manages the hardware and software resources of the computer system. These resources include such things as the processor, memory, disk space, etc. 2. It provides a stable, consistent way for applications to deal with the hardware without having to know all the details of the hardware. Today's major operating systems provide a Graphical User Interface - GUI. ( ) ממשק משתמש להפעלת גרפיקה Elements of a GUI include such things as: windows, pull-down menus, buttons, scroll bars, iconic images. 14 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 human languages, so you need to use computer languages to communicate with them. ● Programs are written using programming languages ( )שפות תכנות. C Java C++ Lisp Pascal VB 15 High level languages vs. machine languages שפת מכונה שפת סף שפת עלית 16 Programming Machine Language Assembly Language Languages High-Level Language ● Machine language is a set of primitive instructions built into every computer. The instructions 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 17 Programming Languages Machine Language Assembly Language High-Level Language ● Assembly languages were developed to make programming easy. Since the computer cannot understand assembly language, however, a program called assembler is used to convert assembly language programs into machine code. For example: to add two numbers, you might write an instruction in assembly code like this: ADDF3 R1, R2, R3 Assembly Source File … ADDF3 R1, R2, R3 … Machine Code File Assembler … 1101101010011010 … 18 Programming Machine Language Assembly Language Languages High-Level Language ● The high-level languages are English-like and easy to learn and program. For example 1: the following is a high-level language statement that computes the area of a circle with radius 5: area = 5 * 5 * 3.1415; For example 2: the following is a high-level language statement that prints the string: PRINT(“Welcome to Java course”); 19 Algorithm ( ) אלגוריתם An algorithm is a procedure or formula for solving a problem. The word derives from the name of the mathematician, Mohammed ibn - Musa al - Khwarizmi, who was part of the royal court in Baghdad and who lived from about 780 to 850. Al-Khwarizmi's work is the likely source for the word algebra as well. Algorithms are implementationindependent. 20 Basic computer operators • INPUT/OUTPUT ( פלט/)אפרטורים קלט • ASSIGNMENT ( ) אופרטורים השמה • ARITHMETIC ( ) אופרטורים חשבון • SELECTION ( ( אופרטורים בחירה • PROGRAM CONTROL ( ) שינוי סדר הוראות operators operators operators operators operators 21 Flowchart elements What do the different flowchart shapes mean ? This shape tells you where the flowchart begins and ends. X = 15 In most flowcharts, the rectangle is the most common shape. It is used to show a process, task, action, or operation. A decision asks a question. The answer to the question determines which arrow you follow out of the decision shape. Grade A parallelogram represents input or output. Lines with Arrows. You read a flowchart by following the lines with arrows from shape to shape. The lines with arrows determine the flow through the chart. 23 Flowchart examples 24 THREE INTEGER’S MAX VALUE (FLOWCHART) 25 PSEUDO - CODE • Pseudo-code is a tool that can be used to express algorithms more precisely. • Pseudo-code is a combination of programming code and ordinary English. • Pseudo-code allows algorithms to be specified precisely without having to worry about programming language syntax. • There is currently no firmly established standard for Pseudo Code. • Pseudo-code is not actually executed on a computer, it simply provides a means for programmers to "Think out" their programs before they implement them. • A carefully prepared pseudo code program can be easily converted to a programming language such as C++ or Java. 26 HOW TO WRITE PSEUDO-CODE • INPUT – READ get input from a file – GET get input from the keyboard • ARITHMETIC / CALCULATIONS – +_ * / ( ) = • OUTPUT – PRINT output to a printer – WRITE output to a file – DISPLAY output to a monitor • STORE – SET total_price to 0 – total_price = cost_price + tax • COMPARE – IF student is part time THEN ADD 1 to part time ELSE ADD 1 to full time ENDIF 27 THREE INTEGER’S MAX VALUE ) ( PSEUDO - CODE .1קלוט שלושה מספרים למשתנים B , AוC - .2השם ערך של Aלמשתנה MAX .3אם B > MAXאז השם ערך של Bל – MAX .4אם C > MAXאז השם ערך של Cל – MAX .5הדפס ערכו של MAX 28 THREE INTEGER’S MAX VALUE ( Java program ) 29 Software Development Process • Understand Problem Definition • Generalize & Decompose the problem definition • Develop Solution Algorithm • Write the Java program Code • Test and Debug the program 30 Why Java? The answer is that Java enables users to develop and deploy applications on the Internet for servers, desktop computers, and small hand-held devices. The future of computing is being profoundly influenced by the Internet, and Java promises to remain a big part of that future. Java is the Internet programming language. Java is a general purpose programming language. Java is the Internet programming language. 31 Characteristics of Java • • • • • • • • • • • Java Is Simple Java Is Object-Oriented Java Is Distributed Java Is Interpreted Java Is Robust Java Is Secure Java Is Architecture-Neutral Java Is Portable Java's Performance Java Is Multithreaded Java Is Dynamic 32 Important Java Concepts and Terminology • JRE is the Java Runtime Environment and it creates a virtual machine within your computer known as the JVM (Java Virtual Machine). JRE is specific to your platform and is the environment in which Java byte code is run. • JDK (formerly SDK) is the Java Development Kit. JDK = JRE + development tools. ▪ IDE is the Integrated Development Environment, have been created to support the development of Java programs. IDEs combine an editor, compiler and other Java support tools into a single application (Eclipse in this course). • To learn more about JDK, JRE, IDE etc., visit http://java.sun.com/javase/technologies/index.jsp 33 Running and Compiling C/C++ Project Library for Linux Linux binary C++ Code Linux executable Linux C/C++ linker Project Library for Windows Windows binary Windows executable Windows C/C++ linker 34 Running and Compiling Java Java bytecode is the form of instructions that the JVM executes Java Code Java interpreter translates bytecode to machine code in JRE javac Hello.java Java compiler Hello.java JRE for Linux Java Bytecode Hello.class JRE for Windows JRE (Java Runtime Environment ) is the base set of data files and programs (executables) which are required to run Java Applications. 35 Eclipse • Eclipse is a multi-language software development environment comprising an Integrated Development Environment (IDE) . • It is written mostly in Java. • Before you can work with Eclipse, you'll need to download the Java Development Kit (JDK). • Eclipse is free software: http://www.eclipse.org/downloads 36 Programming Errors ● Even the most experienced programmers make mistakes, and knowing how to debug an application and find those mistakes is an important part of programming. ● Before you learn about the debugging process, however, it helps to know the types of bugs that you will need to find and fix. 37 Programming Errors • Syntax Errors ( ( שגיאות דיקדוק Java, like all other programming languages, has its own syntax. Syntax errors are a type of compiler error. This means they will be detected immediately when the programmer tries to convert his source code into a program. For example: one rule of Java syntax is that all commands must end with a semicolon (;). • Runtime Errors ( ) שגיאות זמן ריצה A runtime error means an error which happens, while the program is running. Causes the program to abort. • Logic Errors ( ) שגיאות לוגיות These kinds of errors are a lot harder to fix, because you don't necessarily know what causes the error. Produces incorrect result. 38