Lecture 1. A. Sahu and S. V. Rao. Indian Institute of Technology Guwahati

Transcription

1 Lecture 1 Introduction to Computing A. Sahu and S. V. Rao Dept of Comp. Sc. & Engg. Indian Institute of Technology Guwahati 1

2 Outline Computer System Problem Solving and Flow Chart Linux Command ls, mkdir, cp, mv, rm, cat,.. Editor: vi, pico, gedit, kwrite, emacs How to program Write, Compile eand Execute e Explanation of C program Demonstration: if possible 2

3 What Is A Computer? An electronic device Operates under control of instructions (software) Stored in its own memory unit It can Accept data (input), Manipulate data (process), Produce output from the processing. A collection of devices that function together A collection of devices that function together as a system. 3

4 Computer System I/P Processing O/P Keyboard, Mouse : Input Speaker, Monitor/Display : Output CPU Box : Processing 4

5 Computer System: Von Newman Memory I/P Processing O/P Input and Output Processing Memory : Where it store Instruction, Data, Intermediate compute 5

6 Inside PC : Motherboard 6

7 Inside PC: Memory Card 7

8 Inside PC : Hard Disk 8

9 Inside PC : Processor 9

10 Computer System: When you Switch on Operating System boots from Hard disk OS : Give you an environment where you work Different OS Window XP/Vista/7 Linux: Fedora, Ubuntu, Debian Application can be invoked by clicking some icon Application: Word, Excel, Internet Explorer, Mozilla, MediaPlayer 10

11 Screen shot : Window & Linux Both are equally Good and Powerful Window: User friendly, prone to Virus, Commercial (Not Free: you have to Pay Money) Linux : Robust and Freely available 11

12 Application Software Application Software consists of programs That tell a computer how to produce information. Someofthemorecommonlyusedpackages are: Word processing, Spreadsheet Database Presentation graphics 12

13 Word Processing Used to create and print documents. A key advantage of word processing software Users easily can make changes in documents. 13

14 Electronic Spreadsheets Allows the user can do on rows and columns of numbers Add, Subtract, user defined calculations These numbers can be changed Spreadsheet quickly recalculates the new results 14

15 Database Software Allows the user to enter, retrieve, and update data In an organized and efficient manner With flexible inquiry and reporting capabilities. 15

16 Presentation Graphics Allows the user to create documents slides to be used in making the presentations. Using special projection devices to Project Slides display as they appear on the computer screen 16

17 Internet Browsing Allows the user to browse website View HTML pages Play internet video, games, do many things 17

18 How to create your own Application? Operating System : Linux, Window Applications: Word/Excel, Media Player, Mozilla, Explorer, etc We use it to do some tasks, but don t know inside contents Programming helps us to create our own application Already solution approach is known Draw the flow chart, writepseudocode Write code, compile, run and test 18

19 Programming: Purpose? Programming Purpose : to create a program that performs specific operations or exhibits a certain desired bh behavior. Computer Language (C, C++, Java, Fortran, Cobol) Design our own application Almost from the beginning Understanding how software/application works 19

20 How to do programming Problem: Specification Example: Compute sum of firstn natural number Define Input {N}, Output {SUM} How to do : Flow chart Write the C/C++/{*} Code in Note/Paper Program Sequence of Instructions and Data Can be run by Compiling and running Interpreting 20

21 How to do programming OS, Shell, IDE, Editor: Linux, Bash Shell, gedit/vi/pico Word Processor is not used to write program Integrated Development Environment: GUI Based TurboC/VisualC++/Kdevelop/Dev GUI Use the Program (Method 1) Compiling: GCC, TCC, VCC Running:./a.out Use the Program (Method 2) Interpret the program and run 21

22 Interpreter Interpreter Vs Compiler Examples: Shell/Command Prompts, ML, Perl, Python, Matlab Read code line by line and execute, sequential Basic syntax Errors occur at run time Compiler Example: C, C++, Java Read whole code together, make an executable and run the executable tbl Basic syntax Errors don t occur at run time, only logical and runtime error occurs 22

23 Interpreter Interpreter Example Examples: basic command line calculator l of Linux $bc 3* (3+2)^2 31 Doing small computation easier Interpreter can read from file and execute line by line, example shell script 23

24 Writing and Compiling C Program #include <stdio.h> int main(){ under Linux printf( Hello world ); Header file: Standard Input/Output Starting of program } return 0; Printing message End of program 24

25 Compiling program: test.c Compiling : $gcc test.c Listing : $ls test.c aout a.out Execute the program : $./a.out Hello world 25

26 Example 1: Adding two number Flowchart START Step 1: Input A and B Step 2: S A + B Step 3: Print S Input A and B S A + B Print S STOP

27 Sum A+B : Input and output #include <stdio.h> int main(){ int A,B, S; printf( Enter two numbers ); scanf( %d %d,&a,&b); S=A+B; printf( Res=%d, B); return 0; } Header file: Standard Input/Output Printing message Asking for inputs Compute Output Result logical mistake, should 27 be S

28 Compiling program: test.c Compiling : $gcc Wall test.c It is advisable di to use Wall Wlloption to raise all warnings of the code Listing using $ls test.c aout a.out Executing : $./a.out Input two numbers 5 7 Res=12 28

29 C Programming in Liunx Environment We will be using Linux environment in CS110 Lab Editor : vim and gedit Compiler: GCC (Gnu Compiler Collection) You should ldknow a bit of Linux and Linux Command 29

30 Linux Basics Freely Downloadable from websites Available as sets of DVDs and IIT internal site Installation is very simple After installation you can create logins for different users

31 Linux Basics Each user may login by his/her own login and passwd own login area Upon login, default directory is home directory of the user In Computer center, We will provide machine withlinux installed.

32 Screen shot : Window & Linux Both are equally Good and Powerful Window: User friendly, prone to Virus, Commercial (Not Free: you have to Pay Money) Linux : Robust and Freely available 32

33 Linux basics: Command, Shell Basic

34 Linux basics: Command, Shell Basic Whatever you can do by clicking using GUI Same can be done by textual command Doing using GUI and mouse click Is easy and convenient for layman users Internally : Mouse click convert get converted to textual command and execute Textual commands are Faster and easy to understand

35 Linux basics: Shell Basic Command Prompt Linux/Unix i is case sensitive i.e. WHO is not same as who Shell is a command program to communicate with a computer Shell interprets the command that you enter on keyboards Shell commands can be used to automate various programming gtasks

36 Linux commands Usually short and cryptic like vi or rm Commands may also have modifiers for advance options like: ls l and mv R are different that ls or mv respectively

37 Important commands ls: listing of the current directory cp: Copy file from source to destination mv: Move file from source to destination vi, Edit a file. vi is one of the most powerful text editors

38 Important Linux Commands chmod, Change file permissions mkdir, rmdir Make/Remove a directory cd, Change directory rm, Remove a file. Can also remove directory tree man ls, Get help for ls.

39 Command: ls Command to list files and directory ls $ ls Command : ls *.c list all file with extension.c List all C file in the current dirctory Command: ls a* list all the file/directory started with a

40 Wildcards You can substitute the * as a wildcard symbol for any number of characters in any filename. You can mix the * with other characters to form a search pattern: ls a*.txt will list all files that start with a and end in.txt The? wildcard d stands for any single character: ls draft?.doc will list draft1.doc, draft2.doc, draftb.doc,, etc.

41 Control characters You type Control characters by holding down the control key while also pressing the specified character. While you are typing a command: ctrl W erases the previous word ctrl U erases the whole command line Control commands that work (almost) any time ctrl S suspends (halts) output scrolling up on your terminal screen ctrl Q resumes the display of output on your screen ctrl C will abort any program

42 Text Editors Available on Linux Systems Vi/vim Non graphical (terminal based) editor. Guaranteed to be available lbl on any system. Requires knowledge of arcane keystroke commands. Distinctly unfriendly to novices. emacs, gedit, kwrite, pico Window based editor Primitive menus make it slightly more friendly to novices. Emacs: Still need to know keystroke commands to use. Installed on all Linux distributions and on most other Unix systems.

43 File Type and permission $ls l list all file in detail $file test.c executable, text, media, library Attribute of file and directory User, group and others 43

44 Help on command line: Manual page Best local resources in the Linux System man :Typeman and the name of a command to read the manual page for that command. e.g. man ls man mv You can find many web resources on Linux command Basic Linux Command ence.pdf

45 Thanks 45