CISC105 General Computer Science

1. CISC105 General Computer Science Class 1 – 6/5/2006

2. Important Notes! • The lab session has been moved from 040 Smith Hall to 009 Willard Hall. It will meet at the same day and time.

3. Computer Hardware

4. Main Memory • Memory Cells • Address • Memory content • Data • Program Instruction • RAM vs. ROM • Random Access Memory = volatile • Read Only Memory = non-volatile

5. Bits and Bytes • Information stored in memory as bits • 8 bits = 1 Byte • 1 b vs. 1 B • 1 KB = 1024 B • 1 GB = 1024 MB = 1,048,576 MB = 1,073,741,824 B

6. Secondary Storage • Secondary Storage is used for long term storage of programs and information • Information is stored in Files, directories and subdirectories

7. Central Processing Unit (CPU) • “Brain” of the computer with 2 primary functions • Coordinate all computer operations • Performing arithmetic and logical operations on data • CPU follows instructions contained in a computer program • Fetch Instruction -> Interpret Instruction -> retrieve data (if necessary) -> carry out instruction • Uses Registers (high speed memory) to speed up retrieval

8. Input Devices • Input Devices - Any device used to enter information into a computer • Keyboard, Mouse, Digitizer etc.

9. Output Devices • Output Devices used to observe the results of the data manipulation • Monitor, printer, etc.

10. Computer Network • Local Area Network (LAN) – computers and peripherals connected together in order to share resources. Usually contained in a building. • Network Printers, Scanners, secondary storage (file servers) etc.

11. Computer Network (WAN) • Wide Area Network (WAN) – a network that attaches a large number of computers over a large geographic area. • The Internet is the most well know WAN (WWW and GUI via Browser)

12. How to connect to Networks • Modem - Use a telephone line (modulator / demodulator) - transmit up to 50,000 bps • Digital Subscriber Line (DSL) – uses telephone line but can have simultaneous voice communication. (~1.5 Mbps) • Cable Internet access – uses the coax cable that is used to deliver TV to your house

13. Computer Software • Operating System • Application Software • Computer Languages • Software Development Method

14. Operating System • Operating System (OS) - Collection of programs that control the interaction of the user and computer hardware • Booting a computer – loading the OS into memory

15. OS Responsibilities • Communicating with the computer users • Managing memory allocation, processor time and other resources • Collecting input from Input devices • Conveying output to screen, printer, etc • Fetch data from secondary storage • Write data to secondary storage

16. Application Software • Application – software used for a specific task – word processing, email, accounting, etc • Applications are made available by installing them. • Must be compatible with the Hardware and operating system you are using.

17. Computer Languages • Machine language – collection of binary numbers • Only understood by a specific CPU • Not very readable • Not standardized • Assembly Language – mnemonic codes that correspond to machine language • Suffers from same problems as Machine Language

18. Computer Languages • High-Level language • CPU independent • Combine algebraic expressions • A compiler will translate a high-level source file into machine code • Syntax is very important! • Some developers use an IDE to

19. Entering, Translating, and Running a High-Level Language Program

20. Flow of information during program execution

21. Software Development Method • PAD IT Man! • Problem Definition • Analyze the Problem • Design Algorithm • Implement the Algorithm • Test and verify the program • Maintain and Update the program

22. Software Development Method (example) • Problem definition: Your job requires you to convert miles to kilometers. • Analysis: • Program input: distance in miles • Program output: distance in kilometers • Relevant Formula: 1 mile = 1.609 kilometers

23. Software Development Method (example) Design • Get the distance in miles • Convert the distance to kilometers • Distance in kilometers is 1.609 times the distance in miles • Display the distance in kilometers Check the algorithm = 10 miles times 1.609 = 16.09km

24. Software Development Method (example) • Implement and test

25. Chapter 2 • C Language Elements • Variable Declaration and Data Types • Executable Statements • General Form of a C program • Formatting Numbers in Output • Interactive Mode, Batch Mode, and Data Files • Common Programming Errors

27. Variable Declaration and Data Types • Variable – a name associated with a memory cell whose value can change • Variable Declaration – statements that communicate to the compiler the names of the variables in the program and the kind of information it stores. • Data Types – a set of values and operations that can be performed on those values

28. Executable Statements • Assignment Statements – an instruction that stores a value or a computational result in a variable

29. Executable Statements

30. I/O Statements - printf • printf is an output statement supplied by the stdio.h library • printf is executed by running a function call • printf(“That equals %f kilometers.\n”, kms); • Function arguments • Format String (placeholders – multiple placeholders) • Print list • \n and the cursor