1. COMP 14 Introduction to Programming Mr. Joshua Stough January 19, 2005 Monday/Wednesday 11:00-12:15 Peabody Hall 218

2. Announcements Registration – Today is last day to add – Karen Thigpen ( thigpen@cs.unc.edu ) thigpen@cs.unc.edu – HW 0 due today 11:59pm Please pay attention to what you are supposed to name the file. – Questions I responded to? – Office hours: W 9:30, F 12:00, by appointment

3. Questions from Last Time Note announcements on Blackboard Do I need a laptop for COMP 14? Do I need Internet access for COMP 14?

4. Last Time in COMP 14 Syllabus Honor Code Blackboard jGRASP Due today –Homework 0 –Pledge form bring to front at end of class turn in to Sitterson front desk by 5pm today

5. Today in COMP 14 Parts of the computer –hardware vs. software –CPU and memory Binary numbers What is an algorithm? Book references: Chapter 1

6. Reading Check-Up 1.- computer components including the CPU, main memory, I/O devices, and secondary storage 2.- the brain of the computer, containing the CU, PC, IR, ALU, and ACC 3.- computer instructions to solve a problem 4.The digits 0 and 1 are called or the shortened term hardware CPU program binary digits bits

7. Before Programming... You need a basic understanding of how a computer works –if you’re going to drive a car, you need to know that it runs on gasoline... Understanding the pieces will help you understand what your programs actually do Plus, we want you to be able to talk intelligently about computers

8. Hardware vs. Software A computer is made up of hardware and software Hardware Software CPU - ex: 1 GHz Pentium III input/output - keyboard - monitor - network card main memory - ex: 256 MB RAM secondary memory - ex: 20 GB hard drive operating systems - Windows XP - Mac OS X applications - games - Microsoft Word - Internet Explorer

9. Hardware Organization motherboard CPU memory hard drive

10. Central Processing Unit CPU Control Unit (CU) –"the brain" of the CPU Program Counter (PC) –points to the next instruction to be executed Instruction Register (IR) –holds the currently executing instruction Arithmetic Logic Unit (ALU) –carries out all arithmetic and logical ops Accumulator (ACC) –holds the results of the operations performed by the ALU

11. Main Memory Ordered sequence of cells AKA Random Access Memory (RAM) Directly connected to the CPU All programs must be brought into main memory before execution When power is turned off, everything in main memory is lost

12. Main Memory With 100 Cells Each memory cell has a numeric address, which uniquely identifies it

13. CPU and Main Memory Chip that executes program instructions Primary storage area for programs and data that are in active use (RAM) All programs must be brought into main memory before execution

14. Secondary Storage Provides permanent storage for information Retains information even when power is off Examples of secondary storage: –Hard Disks –Floppy Disks –ZIP Disks –CD-ROMs –Tapes

15. Secondary Storage Secondary memory devices provide long-term storage Information is moved between main memory and secondary memory as needed

16. Input Devices Definition: devices that feed data and computer programs into computers Examples: –Keyboard –Mouse –Secondary Storage

17. Output Devices Definition: devices that the computer uses to display results Examples: –Printer –Monitor –Secondary Storage

18. Input/Output Devices I/O devices facilitate user interaction

19. Hardware Components

20. Opening Notepad Use the mouse to select Notepad The CPU requests the Notepad application Notepad is loaded from the hard drive to main memory The CPU reads instructions from main memory and executes them one at a time Notepad is displayed on your monitor

21. Questions 1. - points to the next instruction to be executed 2. - a unique location in memory 3. - stores information permanently 4.Instructions executed by the CPU must be first loaded from program counter (PC) address secondary storage main memory

22. Software Categories Operating System –controls all machine activities –provides the user interface to the computer –first program to load when a computer is turned on –manages computer resources, such as the CPU, memory, and hard drive –examples: Windows XP, Linux, Mac OS X Application –generic term for any other kind of software –examples: word processors, missile control systems, games

23. Operating System (OS) OS monitors overall activity of the computer and provides services Written using programming language Example services: –memory management –input/output –storage management

24. Application Programs Written using programming languages Perform a specific task Run by the OS Example programs: –Word Processors –Spreadsheets –Games

25. Questions Classify the following pieces of software as operating system or application: 1. Microsoft Windows 2000 2. Microsoft PowerPoint 3. Linux 4. Your COMP 14 programs OS app

26. It’s All About Data Software is data –numbers, characters –instructions, programs Hardware stores and processes data –read, write –add, subtract, multiply, divide

27. Analog vs. Digital Analog –continuous wave forms –ex: sound, music on an audio tape Digital –the information is broken down into pieces, and each piece is represented separately –represented as series of 0 and 1 0 - low voltage 1 - high voltage –can be copied exactly –ex: music on a compact disc

28. H i, H e a t h e r. 72 105 44 32 72 101 97 116 104 101 114 46 Representing Text Digitally All information in a computer is digitized, broken down and represented as numbers. Corresponding upper and lower case letters are separate characters.

29. Language of a Computer Machine language: the most basic language of a computer A sequence of 0s and 1s –binary digit, or bit –sequence of 8 bits is called a byte Every computer directly understands its own machine language –why can't Windows programs run on Apple computers?

30. 1 bit 0101 2 bits 00 01 10 11 3 bits 000 001 010 011 100 101 110 111 4 bits 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 Each additional bit doubles the number of possible permutations Bit Permutations

31. 2 1 = 2 items 2 2 = 4 items 2 3 = 8 items 2 4 = 16 items 2 5 = 32 items 1 bit ? 2 bits ? 3 bits ? 4 bits ? 5 bits ? How many items can be represented by Bit Permutations Each permutation can represent a particular item There are 2 N permutations of N bits –N bits are needed to represent 2 N unique items

32. Binary Numbers N bits to represent 2 N values N bits represent values 0 to 2 N -1 Example: 5 bits –32 unique values (0-31) –00000 = 0 –11111 = 31 2 4 2 3 2 2 2 1 2 0 16 + 8 + 4 + 2 + 1

33. Decimal to Binary 114 1110010 NumberPlace ValueDigit 1142 6 = 641 502 5 = 321 182 4 = 161 22 3 = 80 22 2 = 40 22 1 = 21 02 0 = 20

34. Questions Binary Numbers What’s the maximum value a 6-bit number can represent? What’s the decimal representation of 111010? What’s the binary representation of 35? 63 58 = 32+16+8+2 100011

35. KB2 10 = 1024 MB2 20 (over 1 million) GB2 30 (over 1 billion) TB2 40 (over 1 trillion) UnitSymbolNumber of Bytes kilobyte megabyte gigabyte terabyte Storage Capacity Every memory device has a storage capacity, indicating the number of bytes (8 bits) it can hold Various units:

36. Programming Languages Evolution Early computers programmed in machine language (only 0s and 1s) Assembly languages were developed to make programmer’s job easier Assembler: translates assembly language instructions into machine language

37. Assembly and Machine Language

38. Programming Languages Evolution High-level languages make programming easier Closer to spoken languages Examples: –Basic –FORTRAN –COBOL –C/C++ –Java

39. From Java to Machine Language Computers understand only 0 and 1 (machine language) Compiler translates source code into machine code Java compiler translates source code (file ending in.java) into bytecode (file ending in.class) –bytecode is portable (not machine-specific) Java interpreter reads and executes bytecode –different Java interpreters for different types of CPUs and operating systems (OS) Intel/Windows, Motorola/Mac OS X, Intel/Linux

40. Problem Solving The purpose of writing a program is to solve a problem The general steps in problem solving are: –understand the problem –dissect the problem into manageable pieces –design a solution –consider alternatives to the solution and refine it –implement the solution –test the solution and fix any problems that exist

41. Algorithm Sequence of instructions used to carry out a task or solve a problem May be written in either English or pseudocode –outline of a program that could be translated into actual code May need refinement as you work Always write out your algorithm before you begin programming

42. Problem-Analysis-Coding-Execution most important step without computer with computer

43. Algorithm Design Example Problem: Convert change in cents to number of half- dollars, quarters, dimes, nickels, and pennies to be returned. Example: –given 646 cents –number of half-dollars: divide 646 by 50 quotient is 12 (number of half-dollars) remainder is 46 (change left over) –number of quarters: divide 46 by 25 quotient is 1 (number of quarters) remainder is 21 (change left over) –number of dimes, nickels, pennies –result: 12 half-dollars, 1 quarter, 2 dimes, 0 nickels, 1 penny

44. Resulting Algorithm 1. Get the change in cents 2. Find the number of half-dollars 3. Calculate the remaining change 4. Find the number of quarters 5. Calculate the remaining change 6. Find the number of dimes 7. Calculate the remaining change 8. Find the number of nickels 9. Calculate the remaining change 10. The remaining change is the number of pennies.

45. Program 1 and Homework 1 Smith Center Banners –posted on Blackboard Book problems: Ch.1 and first part of Ch. 2. Make sure program compiles and runs Don't forget to answer questions that are asked in instructions Due Wednesday 26 th at 11:59pm Turn in pledges.

46. What’s Ahead... Java Basics Reading: Ch 2 (pgs. 21-37) Program 1 due on Wednesday, 26 th Homework 1 due on Wednesday, 26 th

47. Remember Pledge form Attend recitation. Bring paper copies of the programs for that day that would help you. Follow instructions in the assignment. Follow the file naming format. Jar your code files.