1. ICS 102 Computer Programming University of Hail College of Computer Science & Engineering Computer Science and Software Engineering Department

2. Chapter1 : Introduction ICS 102 Computer Programming

3. ICS102: Computer Programming 3 Components of a Personal Computer Questions : - what are the input devices ? - what are the output devices ?

4. 4 A motherboard, provides the electrical connections by which the other components of the system communicate and hosts the central processing unit as well as other subsystems and devices. Motherboard

5. ICS102: Computer Programming 5 Motherboard example : Acer E360

6. ICS102: Computer Programming 6 CPU (Central Processing Unit) The Central Processing Unit (CPU) or processor is the portion of a computer system that carries out the instructions of a computer program and is the primary element carrying out the computer's functions. In an addition operation, the arithmetic logic unit (ALU) will be connected to a set of inputs and a set of outputs. The inputs provide the numbers to be added, and the outputs will contain the final sum. Example: (3 + 2) = 5 3 2 5

7. ICS102: Computer Programming 7 CPU memory ◦ Registers ◦ Cache Main memory (RAM): ◦ Data has to be in main memory so that CPU can access it ◦ Volatile: lost when program exits; computer shuts off Hard Disk, CD, etc. ◦ This is where you keep the data for long-term storage Memory  Memory refers to computer components, devices, and recording media that hold digital data used for computing for some interval of time.  There are mainly three types of memory :

8. ICS102: Computer Programming 8 Main Memory … 1002 1003 1004 1005 Cell Address Memory is divided into Many memory locations (cells) Each memory cell has a numeric address, which uniquely identifies it Each cell contains a data value, e.g. 22

9. ICS102: Computer Programming 9 Main Memory …

10. ICS102: Computer Programming 10 The word “Hello.” stored in 6 memory cells Main Memory …

11. Memory units : Bits and Bytes Bit -- most basic unit of memory ◦ 1 or 0, on or off 1 Byte = 8 bits In a computer, data values are stored as a sequence of bits ICS102: Computer Programming 11 2 7 1004 1005 00000010 00000111 1004 1005

12. ICS102: Computer Programming 12 Program / CPU / Memory Interaction Example: ◦ Input read a number from keyboard ◦ Add 1 to it ◦ Output it on screen Keyboard RAM 1 1 CPU RAM 2 Monitor 1 22

13. 1-13 Software  Software is the programs and data that a computer uses.  Both programs and data are saved in computer memory in the same way.

14. 1-14 Computer Software Types of software Software

15. 1-15 Software Application ProgramsSystems Programs  Word processors  Game programs Spreadsheets Data base systems Graphics programs Web browsers  Operating system. Networking system. Programming language software. Web site server. Device drivers.

16. What is programming?

17. ICS102: Computer Programming 17 What is a program? A (software) program is a list of instructions intended to a computer A program has inputs and outputs Each instruction tells the computer to do something (an action, a calculation, a comparison)

18. ICS102: Computer Programming 18 Program Execution A program tells the CPU how to manipulate and/or move information Programming is about processing information ◦ Take some input, ◦ manipulate it in some way, and ◦ produce a particular output Manipulation Inputs Outputs Program

19. ICS102: Computer Programming 19 Example 1 : Recipe for Scrambled Eggs Ingredients (Inputs) : two eggs, tablespoon of oil, salt Instructions (program): ◦ Add oil to pan ◦ Heat pan on stove ◦ Crack eggs into pan ◦ Add salt ◦ Mix until light and flakey Output: scrambled eggs

20. ICS102: Computer Programming 20 Example 2 : Currency Exchange Input: ◦ Amount ◦ Source Currency ◦ Desired Currency Instructions ◦ Look up in table current exchange rate for the selected currencies ◦ Calculate result as amount * exchange rate Output: result Task : convert an amount of money in some currency (e.g. US Dollars) to another one (e.g. Saudi Riyals).

21. ICS102: Computer Programming 21 Programming language A programming language is the language used to write programs A programming language employs a set of rules that dictate how the words and symbols can be put together to form valid program statements A programming language has a syntax and semantics In this course we focus on Java programming language.

22. ICS102: Computer Programming 22 Java Java is a programming language originally developed by James Gosling at Sun Microsystems It was first released in 1995. The language derives much of its syntax from C and C++. But has a simpler object model and fewer low-level facilities than C and C++.

23. Programming Language Hierarchy

24. The highs and lows of programming languages... High-Level Language (HLL) ◦ closest to natural language ◦ words, numbers, and math symbols ◦ not directly understood by hardware ◦ Java, C/C++, COBOL, FORTRAN, BASIC, Lisp, Ada, etc. Machine Language (lowest level) ◦ natural language for hardware ◦ just 0s and 1s ◦ directly understood by hardware

25. Assembly Language (middle level) a more or less human readable version of machine language words, abbreviations, letters and numbers easily translated from human readable to machine executable code

26. Getting from Source to Machine Code “Compiler” a program that translates HLL source code to machine (object, or executable) code. “Assembler” a program that translates assembly source code to machine (object, or executable) code.

27. Compilers vs. Assemblers vs. Interpreters Compilers and Assemblers ◦ translation is a separate user step ◦ translation is “off-line,” i.e. not at run time Interpreters ◦ interpretation (from source to object code) is not a separate user step ◦ translation is “on-line,” i.e. at run time Compiler, Assembler, or Interpreter Source Code Object Code

28. Java Program Translation Intermediate Code: “Byte Code” ◦ similar to assembly code, but hardware independent Interpreter translates from generic byte code to hardware-specific machine code Java Program Data for Java Program Java Compiler Byte-Code Program Byte-Code Interpreter Machine-Language Instructions Computer Execution of Machine-Language Instructions Output of Java Program Java Virtual Machine

29. Byte-Code and the Java Virtual Machine The Java compiler translates Java programs into byte-code, a machine language called the Java Virtual Machine ◦ Once compiled to byte-code, a Java program can be used on any computer, making it very portable 1-29

30. ICS102: Computer Programming 30 Portability of Java Classical model : Java model :

31. Program terminology Code: A program or a part of a program Source code (or source program): A program written in a high-level language such as Java ◦ The input to the compiler program Object code: The translated low-level program ◦ The output from the compiler program, e.g., Java byte- code 1-31

32. 32 Portability of Java Write once, run anywhere: Because applications written in the Java programming language are compiled into machine- independent bytecodes, they run consistently on any Java platform.

33. 33 A Java Program A Java program consists of one or more classes A Java class consists of one or more methods A Java method consists of one or more statements A Java Program Java classes Java Methods

34. 34 A Java Program A Java program resides in one or more files. The file name of a Java program has extension.java. One of the classes of a Java program is called the driver class. The name of the driver class must be the same as the name of its Java file. (Java is case sensitive. So EX1 is different from ex1.) The driver class must contain a method called main. The execution of Java program starts from the main method of the driver class.

35. 35 Example of a Java Program

36. 36 Example of a Java Program Class name Main method Instruction Class body

37. ICS102: Computer Programming 37 Example of a Java Program Also notice: Curly braces { }

38. 38 Example of a Java Program Also notice: Parentheses ( ) Curly braces { }

39. 39 Example of a Java Program Also notice: Parentheses ( ) Curly braces { } Square brackets [ ]

40. ICS102: Computer Programming 40 Example of a Java Program Also notice: A pair of braces { } define a block

41. Compiling and running a program Type in your program Save the program ◦ Store all your files in one directory for now ◦ Give the program the same name as the class Compile the program ◦ this produces a.class file ◦ Translates the program into something the computer can understand and execute (Java bytecode) Run the program Observe the result and adjust the program if necessary ICS102: Computer Programming 41

42. Edit ICS102: Computer Programming 42 Text Editor Public class /* firstProg.java Public class firstPtog /* This program is an … */ public static void main… /* Program statements g … System.out.print(“Wel … }

43. ICS102: Computer Programming 43 Compile - With Errors firstProg.java Public class firstPtog /* This program is an Arit */ public static void main /* Program statements g System.print(“Welcome } Compiler Errors and Warnings ------------------- Error : The method print( String) is undefined for Type System

44. ICS102: Computer Programming 44 Compile - Success firstProg.java Public class firstPtog /* This program is an Arit */ public static void main /* Program statements System.out.print(“Welcome”); } Compiler firstPtog.class 001011010001011101 1011010001011101110 101000101110111010110100010 111011101011010001011101110 101101000101110111010110100 010111011100010111011101011 010001011101110010111011101 011010001011101110010111011 101011010001011101110010111 011101011010001011101110010 111011101011010001011101110 0101110

45. Run Program ICS102: Computer Programming 45 Welcome to the Arithm The date is Monday Sep What is your name?Fred Well Fred, after a day The cube appears to be You find a Green door, The door closes behind There is a feel of mat firstProg Fred 1