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ICS 102 Computer Programming

University of Hail College of Computer Science & Engineering Computer Science and Software Engineering Department. ICS 102 Computer Programming. ICS 102 Computer Programming. Chapter1 : Introduction. Components of a Personal Computer. Questions : what are the input devices ?

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ICS 102 Computer Programming

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

  2. ICS 102 Computer Programming Chapter1 : Introduction

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

  4. Motherboard 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.

  5. Motherboard example : Acer E360 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. Example: (3 + 2) = 5 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. 3 5 2 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 computercomponents, devices, and recording mediathat hold digital dataused for computing for some interval of time.  There are mainly three types of memory : ICS102: Computer Programming

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

  9. Main Memory … ICS102: Computer Programming

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

  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 1004 2 1004 00000010 1005 1005 7 00000111 ICS102: Computer Programming

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

  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. Computer Software Types of software Software

  15. Software

  16. What is 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) 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 Program Manipulation Inputs Outputs 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 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). 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. ICS102: Computer Programming

  22. Java • Javais a programming languageoriginally developed by James Goslingat Sun Microsystems • It was first released in 1995. • The language derives much of its syntaxfrom C and C++. • But has a simpler object modeland fewer low-level facilities than C and C++. ICS102: Computer Programming

  23. Programming Language Hierarchy

  24. 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 The highs and lows of programming languages ...

  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 Object Code Source Code

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

  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

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

  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

  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. 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. 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. Example of a Java Program

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

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

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

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

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

  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

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

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

  44. Compile - Success Public class firstPtog /* This program is an Arit */ public static void main /* Program statements System.out.print(“Welcome”); } } 001011010001011101 1011010001011101110 1010001011101110101101000101110111010110100010111011101011010001011101110101101000101110111000101110111010110100010111011100101110111010110100010111011100101110111010110100010111011100101110111010110100010111011100101110111010110100010111011100101110 Compiler firstProg.java firstPtog.class ICS102: Computer Programming

  45. Fred 1 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 Run Program ICS102: Computer Programming

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