COMPUTERSCIENCE-NOTES @compscience-notes-blog - Tumblr Blog

Posts

Notesformsc has lot of study materials to learn Computer Science and Programming - C/C++, Java, HTML, CSS, JavaScript. CS topics like Digital Design, Operating Systems, Computer Organization, Networking. We also have lot of programming examples, problems and their solutions.

Only Computer Science has the Answer

This is my other site which has study materials for computer science.

Quizzes

Inserting Date in Oracle 10g XE table

We will create a table and then add a data type 'DATE', but in Oracle 10g or higher version does not take values for Date type easily.Our purpose is not to explore the details of this data type right now. That would be topic for another blog post. As a newbie to Oracle, I had a very hard time figuring , to insert Date type value to my table in Oracle 10g XE. I am sure lot of people new to Oracle would experience similar problem. To cut long story short, let us create a table 'SUPERVISOR' with a field with DATE type.

Create a Table - Supervisor

Inserting values in SUPERVISOR table

Now if we insert values in SUPERVISOR table using DML commands as follows.

Error while inserting values

We receive the error "Not a valid Month" which means the date entered is not recognized as a valid value. So, how do we enter the date values ? Below is the example of correct syntax to enter date values into SUPERVISOR table.

Use To_Date to enter date values

Other Formats of TO_DATE ()

There are other formats of that you can use if inserting dates using TO_DATE function. For example,

you can use TO_DATE('3/5/2012',DD/MM/YYYY') for to enter date.

Let see an example,

Enter Date in a different format

It does not matter if the date is entered in a specific format. The date is displayed in a specific format (DD-MM-YY). You can change the date format by changing the NLS_Parameters of TO_DATE();

#Programming #DBMS

Understanding Structure Array

Introduction

In C programming, the structure is very useful when you have to deal with heterogeneous data types. Only C++ implements multiple data types in class. The structure implementation becomes complex when we use an array of structure. Consider an example program which implement a simple array of integers. I am using Turbo C++ compiler. /* Program to implement a simple integer array */ #include main() { int i,arr[10]={1,2,3,4,5,6,7,8,9,10}; int *p; clrscr(); for(i=0;i<10 br="" i=""> { p = &arr[i]; printf("%u\n",p); 10> getch( ); return 0; } Output:

The output shows that each element of array took 2 byte of data address space. For example, Starting address of arr[0] = 65504 Starting address of arr[1] = 65506 . . . . . . Starting address of arr[9] = 65522

Array of Structure

The array of structure is similar to simple one dimensional array, but the size of array depends on size of structure. This is because structure contains heterogeneous data types. Consider an example, we defined a structure for Student with name, registration no, student marks and grade. Each of the variable with different data type. Name 20 byte because char take 1 byte. Regno 2 byte because int take 2 byte. Marks 2 byte Grade 1 byte _______________ Total 25 byte We will verify this using the following Program which uses array of structure. /* Program to implement Array of Structure */ #include #include struct student{ char name[20]; int regno; int marks; char grade; }; main() { struct student stu[5]; int i; struct student *p; clrscr(); for(i=0;i<5 br="" i=""> { p = &stu[i]; printf("%u\n",p); } getch(); return 0; }5> OutPut:

This time we will consider the total size of array in bytes, which is 25 bytes per structure element. For example, Starting address of stu[0] = 65398 Starting address of stu[1] = 65423 . . . . . . Starting address of stu[4] = 65498

How to access array of structure elements and their properties ?

Here is an example program that use array of structure to compute grade of students.

/* Program to compute the grade of a student using array of structure */

#include #include struct student{ char name[20]; int regno; int marks; char grade; }; main() { struct student stu[5];

int i;

clrscr();

printf("READ STUDENT INFORMATION:\n");

for(i=0;i<5 i="" span="">5>

{

printf("NAME:");

scanf("%s",&stu[i],name);

printf("REGNO:");

scanf("%d",&stu[i].regno);

printf("MARKS:");

scanf("%d",&stu[i].marks);

}

/* Compute Student Grade */ for(i=0;i<5 br="" i=""> {5>

if(stu[i].marks < 50 )

{ stu[i].grade = 'F';

}

else if(stu[i].marks > 50 && stu[i].marks < = 70)

{

stu[i].grade = 'C';

}

else if(stu[i].marks > 70 && stu[i].marks <=80 )

{

stu[i].grade = 'B';

}

else if(stu[i].marks > 80 && stu[i].marks <= 100)

{

stu[i].grade = 'A';

}

/* Print Results */

printf("Name\tRegno\tMarks\tGrade\n");

for(i=0;i<5 i="" span="">5>

{

printf("%s\t%d\t%d\t%c\n",stu[i].name,stu[i].regno,

stu[i].marks,stu[i].grade);

} getch(); return 0; }

Conclusion

The array of Structure is very useful in C because it simplify a complex data structure for easy manipulation. But it has it's own disadvantage. If the array is static there is not problem, but when the array size exceed memory then program will crash due to insufficient allocation.

We could use pointers to structure in order to solve the dynamic memory allocation problem or use similar techniques. C programming, support dynamic memory allocation using malloc( ), alloc( ),etc;

#Programming #DBMS

Understanding Bubble Sorting Algorithm

Setup Oracle DBMS for Lab Practice

It is very important for students to practice SQL to learn RDBMS concepts. It is not enough to read the theories given in books and listen to lectures. Learn by doing helps understand the topic quickly. To practice DBMS labs on you personal computer, one must install a DBMS software such as SQL, MySQL, DB 2 and Oracle. Oracle is very popular and standard software with all the relational DBMS features. It is very good for practicing DBMS labs. Other systems are equally good and there are may Standard products, so one must choose according to their own choice. All of them can run fundamental SQL commands.

To setup Oracle for lab practice you need to following :

1. Download the latest Oracle software :

You can get the latest Oracle software from their web site. The size of the software is large if you download the full version. Since we are only downloading for practice download the Oracle Express edition which is a compact version of the Oracle.

There are three types of download available, they are as follows

Windows version for 64 bit systems.

Window version for 32 bit systems.

Linux / Unix version

Oracle Database Express Edition 11g Release 2

Oracle Database Software Downloads

For purpose of this article, I have downloaded Oracle 10g Express edition which is no longer from their website and in rest of the article we will configure it so that you run SQL queries on it.

2. Install the Oracle software on you personal computer.

Once downloaded run to install the software on you personal computer. You may have a different version of setup , but when you click on it then you should see the installation wizard.

After the installation you may see that startup menu have new icons.

Startup menu have new Oracle programs

Click the start database, to start the database and work on it. It you want to stop the database just click on the stop database. By default the database get started automatically.

Now Click 'Go To Database Home Page', this will open a web interface for Oracle database. You need to Log In to the database using user name and password.

Username : system

Password: < this is password that you entered during Installation >

Oracle 10g XE Home Page

SQL option on the Home page is to run DDL and DML commands and Administration page is maintain database and users. There are many privileged users by default. Here is list of default users for the Database. Also you can create new users for the database with different access levels.

DB Users

3. Configure the SQL Command Line

The command line utility is very useful for running SQL commands and Queries. You need to configure the SQL command line interface, there is not need to configure Environment path to run SQL command line in Windows.

SQL Command Line

The SQL command line is row command mode and that's why we will use a utility called SQLPlus to run the SQL queries using command line interface.

For more information you can visit : Configuring SQL *Plus

The SQL *Plus is already part of your installation, but there is also a downloadable package for SQL *plus which you can download according to your need.

Instant Client Downloads for Microsoft Windows (x64)

The information to use the Client is available in Sqlplus_user guide.

/manual/sqlsplus_ug.pdf

4. Configuring SQL plus IDE

The command line interface of SQL *plus is not interactive. To make it interactive we have to download another utility called the sqlplusw.exe. It is available in most of the Oracle database softwares. The sqlplusw is located in \oracle\product\10.2.0\server\BIN folder.

Right click on the Sqlplus software and make a shortcut to desktop. You can then change the ICON and screen options for SQL Plus.

sqlplusw.exe property

5. Test Logon using sqlplusw

Now that we are ready to run SQL Plus. Click on the shortcut created earlier and run it. You should be able to see the logon window.

SQL *Plus Logon

Enter the credentials for system and password specified during the installation. I have not specified any Host String for the database. So I have not entered any during logon process.

The system account have DBA rights. If you are not able to logon make sure that you have TNSNAMES.ORA file in following location.

oracle\product\10.2.0\server\NETWORK\ADMIN

After you have logon to the SQLPLUS , you should see the screen shown below.

Oracle SQL plus

6. Create a Table

Once you have completed the installation then go ahead and run DDL command and create a table to test it.

for example, run following command to Create a table.

CREATE TABLE ( ROLLNO NUMBER(3), NAME VARCHAR2(15), MARKS (IN %) NUMBER(2), GRADE VARCHAR2(1));

Create a new table

Conclusion

You may experience problem with the installation sometimes or sometimes there may be issues with logon. Make sure that use an account that have full access to the database. The 'system' account has full privilege to the database.

#DBMS

Shortcut to compute nth factorial

Factorial is very important concept in mathematics and computer science. So nth-factorial is denoted by N! and there are other notations too.It is used in permutation,combination and other areas of mathematics. N! us multiplicative result of all numbers up to N. N! = 1 x 2 x 3 x ......x (n-1)(n)

Newer Method

Another way of getting the N! is use the following formula.

For Example: computer factorial of n = 10; 10! = 1 x 2 x 3 x ......x 9 x 10 = 990

Study Tips: Note Making

Note making is the most important task for studying. Your performance in tests depends in this skill. To remember something we must relearn and practice them repeatedly, Until it become our second nature.Study Notes help us to reach that goal.

Difficulties in Note making

Common difficulties in note making is, to decide whether notes prepared by the students will guarantee them success in exams.

Another thing which confuse many students is the style of note making. There are many ways to wrote Notes. Students ask these questions frequently.

Should we note down word to word or just the important points?

What if I miss important points ?

Is it better to make notes from text book and skip the lecture notes? Shall I copy notes from other people ?

Answers to question is, "Notes are pointers which help you remember the whole structure of text book chapter or Lecture".

Notes should be written in form of pointers. Students have to go through lot of academic material during a course. It is not possible to write down everything or memorize them.

Most people who have problem with reading and writing skills are always doubtful of their Notes.

Why make notes and what mistakes students do?

We make notes as proof of our understanding.You should be able to recall everything you studied, just by looking at your notes.So write your own notes.

Student often make mistake by copying other people work or writing note without understanding anything from it.

Note making skill is related to the ability to reproduce your learning during exams, Otherwise it's of no use.

This means you should develop the skill of writing as well. If your writing is not good, it is not possible to take good notes, also not possible to write essays using the notes.

Understanding

Understanding means that visualizing the concepts. Students can only understand when they are able to visualize the learning.

More deeper learning take place when relate information. This would be the best time to note down your understanding. This means you may have to go through the material multiple times.

Review

After you have taken notes from your understanding, you need to review it periodically. The review process is passive most of the time. It does not have to be that way.Without looking at the material, you try to reproduce it.

When you successfully reproduce the work. Writing answers to questions comes naturally.That's another way of reviewing. That is, practice writing answers to questions. Short answer questions / long answer questions or multiple types.

How to take notes ?

To take effective notes, we follow certain guidelines. The guidelines are regardless of which course you are studying. You may know them already, so here it is

Headings and Subheadings

Heading are to categorize the topic you are writing about. If you want to refine your category - you create more subheadings.

Write notes means either you write phrases or simple sentences which make sense. You can assist your notes with suitable Diagrams or Pictures.

Formulas and Definitions

Memorize facts and formulas as it is. You must include them in your notes without making any changes.

Math and Problem Based Learning

Math need lot of practice and need practice in ordered fashion way, because you cannot skip a topic and move on to the next until you understand the previous one. Problem based learning need more effort. Keep a set example problems for each topic learned.

Problem Set

Also, students need to create problem sets to go through them during test.The idea here is to keep the solution of worked out problems in notes.

When you work them again before exams, you may not have to struggle for the steps involved in the solution, because you have them already.

Hope you like these tips , Please subscribe for more.

#Study Tips

Microprocessor Operation -Instruction Execution

Microprocessor has 6 general purpose registers including Accumulator. These register store 8 bit and 16 bit data individually or in pair.

What is H-L register pair used for ?

Answer : The register pair H-L is widely used for the register indirect addressing. All instruction that involve

Data transfer to/from memory

Without mentioning register pair

Or just containing memory address

2. What is meant by incrementing program counter(PC)?

Answer : Program Counter is a 16 bit register which points to the next instruction to be executed.

3. How to identify the operation of an instruction?

Answer : Any operation involving memory or memory addresses, it is stored in the H-L pair. Any operation involving memory or memory addresses, it is stored in H-L pair. Any Microprocessor instructions that have data along with the instruction have to an immediate instruction. Instruction involving Register is Direct.

Instruction Execution

Microprocessor instructions are executed and require certain machine cycle with T-states. Two stages of executing instruction are Opcode fetch and Oprand fetch and execute.

Machine Cycle has 'n' T states.

A machine cycle has 'n' T-states. Machine cycle 1, Opcode is fetched and decoded requires 4 - 6 t-states. In other Machine cycle, data is fetched and executed which require 3 t-states.

Machine Cycle

Calculating clock period

Clock frequency of system = 2 MHz

Clock Period T = 1 / f = 1/2 x 10^ -6 = 0.5

Example

Time to execute a command MVI = 7 t-states x 0.5 = 3.5 μs

Task : Find why we need 7 state for MVI instruction.

Importance of calculating clock period

Calculating clock period is important in a microprocessor based program with loop or counter.

Time Delay in Loop TL

TL = (T x loop T-states x N10)

T = System Clock period = 2 MHz

N10 = Decimal equivalent of Hexadecimal count loaded in register.

Adjusted Loop Delay

TLA = TL - (T-states x Clock Period)

Total Delay

TD = T0 + TLA

Bibliography

Kant, K. (2010). An Introduction to Microprocessors and Applications. McMillan.

#Programming #Microprocessor

MATRICES

Matrices are linear equations and linear functions, which are represented in tabular or matrix form. Matrix has row and columns. So, as if we say m x n matrix mean that the matrix has

m = rows

n = columns

Linearity of function which meet two condition most of the time,

f(x + y) = f(x) + f(y)

f (ax) = a f(x)

linear transformation happens when linear function changes with some operations.

Example of a linear function

2x + y = 3 where x and y both have value 1.Thus the equation have a solution

x =1 and y =1 which satisfy 2x + y =3.

Graph of Linear Equation

While plotting graph, we want the

y value = x value, actually it is f(x) = x means [what value of x will give me y?]

If we plot the graph of 2x + y = 3, it is y = 3-2x which means if 'x' is 1, then y =1

Using this we can plot the graph, if we look at the graph it is value of y is decreasing function. So a function can be negative or positive.

Matrix: a system of linear Equations

The above two dimensional graph is a Cartesian co-ordinate system. We understand from above figure that there could be many equations and solution to the graph and very difficult to manage or manipulate.

2x + y = 3 can be represented in a matrix form.

Many Equations can have same or different solutions, so we write them as

2x + y = 3

5x - 2y = 3

A matrix representation of linear equation

Unknown variables

If we observe then we have two unknown variable [x and y] in the linear equation and once we identify these variables and satisfy the equation we can say that the SOLUTION to the system of equation is found.

#Mathematics

Pointer to Fuctions in C/C++

Pointer is very important concept in C/C++ programming. A pointer is memory location that points to memory location of another variable. Visualizing the function of pointer gives a clear understanding of how it works and can be very helpful in constructing efficient programs. Lets see the Our Example code and Diagram of Pointer to function.

#include main() { int a,b,c,mul(int a,int b); // assign values a = 10; b = 20; int(*p)(int ,int) ; //our pointer to function p = mul(int a, int b); // initialize pointer c = (*p)(int ,int); // assigning value of pointer // to c printf("%d\n",c); // print the result } // come to function mul() mul(int a , int b) { return( a * b); } // This will return the value to // the LOCATION where pointer // points to Hope you like this, Please send your comments .

#Programming #Algorithms

Pointers Accessing different Data Types

One of the most difficult task while learning C/C++ Programming is to master Pointers. A Good programmer is C/C++ is one how knows how to extensively work with Pointers.For Starters, Let us see how an example of pointers accessing other data-types. #include struct store { int id; float price; char name[10]; }; main() { int x,i; /* declare variables before */ char name[10];/*pointers */ static int array[4]= { 29,44,44,23}; struct store data; int *p ,*q;/* then declare pointers */ char *m; struct store *y; /* * all types of pointers are now initialize * */ x = 10; p = &x;/* holds address of x */ printf("%d",*p);/* prints 10 */ strcpy(name,"Jesus"); /* assign value to name */ m = name; printf("%s",*m); /* prints Jesus */ for(i=0;i<4;i++) { /* p= array[0] is 1st */ p = array[i]; /* prints all array */ printf("%d\n",*p);/* values in line */ } data.id = 10;/* assign value to all value*/ data.price = 20.33; /* in struct stores */ strcpy(data.name,"harry potter"); y->id = data.id; /* assign values to pointer */ y->price = data.price; strcpy(y->name,data.name); printf("%d\n",y->id); printf("%f\n",y->price); printf("%s\n",y->name); return 0; } References:- E. Balagurusamy, Programming In Ansi C, 5E, Tata McGraw-Hill Education

#Programming #Algorithms

Introduction to Software Engineering

Software Engineering - What is it?

Have you ever thought how those complex Software Packages are made? The techniques used in making these software products are the basis for Software Engineering.

Software engineering is past experiences arranges in methodologies and guidelines. Without using principles of software engineering building a large software program is difficult. We need more than just common sense.

Large programs are complex and software engineering reduces complexity using two methods.

Decomposition

Abstraction

Abstraction take account of only those aspects of software engineering with is relevant to the tasks.

Once simple task is completed, another level of abstraction is taken into account.

Decomposition is to break the large program into smaller tasks. We can treat each task as a small problem to solve independently.

Software Engineering problems

Software and Hardware costs are increasing day by Day because of poor use of resources, Cost overruns due to lack of training in software development, skill shortage and time to develop software.

All amount to low productivity. Solution to these problems would be increasing awareness of Software Engineering principles and practices.

Difference between Program and Software product

Programs developed by individuals for their personal use mostly. They are limited in tasks and easier to develop. Software products are large and complex and people involve in are not the same person but they are normal users. Software product user interfaces are also designed carefully for the same reason.

Bibliography

Kharagpur, I. (n.d.). Software Engineering. Retrieved from Nptel: nptel.ac.in

#Software Engineering

Functional Oriented Software Design – Data Flow Diagram

In Structured analysis phase we

Graphically presented information

Each function is decomposed in more detailed functions

What are DFDs?

Also known as bubble chart

Symbols used for data flow diagram and are independent.

Related to software designs.

It is simple to use.

Data dictionary and its importance All data item that would appear in DFDs. Uses data definition operators to show composition of data items. - a+b show a and b.

Importance: standard terminology and definition of data structures.DFD is balanced: Input and output of DFD must match with the next level of the DFDs.DFD model of a system

What is a context diagram?

It is abstract data flow representation of a system.

It is also called level 0 DFD

The most abstract data model of the system is context diagram.

How to create DFD model of any system?

A DFD model of a system graphically depicts transformation of data input to the system to the final output.

Then develop level 1 DFD - examine high level functional requirements.

Each bubble at any level is then decomposed in to several levels called factoring or exploding the bubble.

Bubbles are numbered 0.1,0.2 etc and there sub levels x.1,x.2 etc

Develop data dictionary for any given problem?

List all the data items in DFDs.

Common error during DFD creation

Context diagram should depict the single bubble.

External entries should be shown in context diagram.

Unbalanced DFDs

Control information in DFD like error messages.

DFD is only data flow model

No other information other than SRS

What is the Shortcoming of a DFD Model?

Not precise

No control aspect - like error messages

Several possibilities of the same diagram

Bibliography

Kharagpur, I. (n.d.). Software Engineering. Retrieved from Nptel: nptel.ac.in

#Software Engineering

Basic Logic Gates

We will start with some definitions.

Definition: A gate is a logic circuit with one Output and one or more Input signals.

Logic Gates

OR Gate

AND Gate

NOT Gate

OR Gate:

An OR Gate

An OR gate has always high output ( In binary it;s 1) if one of it's input is high( again binary 1). Truth Table for an OR gate

OutPut

AND Gate:

AND Gate

AND Gate has high output when both of it's inputs are high, otherwise output is low( means binary 0).Truth Table for an AND Gate:

OutPut

Not Gate:

NOT Gate

Output from Not gate are complement of Input.Truth Table for a NOT Gate:

OutPut

0Bibliography

Mano, M. (1994). M.M. Mano, Digital Logic and Computer Design,. Prentice Hall of India.

Shjiva, S. G. (1998). Introduction to Logic Design 2nd Edition. Marcel Dekker, Inc.

#Digital Design

Computer Graphics Terminology to Remember

Modeling co-ordinate

Not to be confused with desktop windowing systems ( MS Windows or X Windows ), this coordinate system refers to the subset of the overall model world that is to be displayed on the screen. Depending on the viewing parameters selected, the model window may be rectalinear or a distorted viewing frustrum of some kind.World co-ordinate

Also known as the "universe" or sometimes "model" coordinate system. This is the base reference system for the overall model, ( generally in 3D ), to which all other model coordinates relate.affine - Allowing for or preserving parallel relationships.Arbitrary - Based on random choice or personal whim, rather than any reason or system.shear - A strain produced by pressure in the structure of a substance, when its layers are laterally shifted in relation to each other.Multiple Coordinate Systems in a Graphics Program

In a typical graphics program, we may need to deal with a number of different coordinate systems, and a good part of the work ( and the cause of many headaches ) is the conversion of coordinates from one system to another. We'll learn about the conversion process a little later, but in the meantime, here is a list of some of the coordinate systems you may encounter:

World Coordinate System

Also known as the "universe" or sometimes "model" coordinate system. This is the base reference system for the overall model, ( generally in 3D ), to which all other model coordinates relate.

Object Coordinate System

When each object is created in a modelling program, the modeller must pick some point to be the origin of that particular object, and the orientation of the object to a set of model axes. For example when modelling a desk, the modeller might choose a point in the center of the desk top for the origin, or the point in the center of the desk at floor level, or the bottom of one of the legs of the desk. When this object is moved to a point in the world coordinate system, it is really the origin of the object ( in object coordinate system ) that is moved to the new world coordinates, and all other points in the model are moved by an equal amount. Note that while the origin of the object model is usually somewhere on the model itself, it does not have to be. For example, the origin of a doughnut or a tire might be in the vacant space in the middle.

Hierarchical Coordinate Systems

Sometimes objects in a scene are arranged in a hierarchy, so that the "position" of one object in the hierarchy is relative to its parent in the hierarchy scheme, rather than to the world coordinate system. For example, a hand may be positioned relative to an arm, and the arm relative to the torso. When the arm moves, the hand moves with it, and when the torso moves, all three objects move together.

Viewpoint Coordinate System

Also known as the "camera" coordinate system. This coordinate system is based upon the viewpoint of the observer, and changes as they change their view. Moving an object "forward" in this coordinate system moves it along the direction that the viewer happens to be looking at the time.

Model Window Coordinate System

Screen Coordinate System

This 2D coordinate system refers to the physical coordinates of the pixels on the computer screen, based on current screen resolution. ( E.g. 1024x768 ).

Viewport Coordinate System

This coordinate system refers to a subset of the screen space where the model window is to be displayed. Typically the viewport will occupy the entire screen window, or even the entire screen, but it is also possible to set up multiple smaller viewports within a single screen window.

Bibliography

jbell. (n.d.). Coordinates. Retrieved from ComputerGraphics: http://www.cs.uic.edu/

M.P.Baker, D. a. (1997). Computer Graphics. Prentice Hall of India .

Wikipedia. (n.d.). Coordinate_System. Retrieved from Wikipedia: http://en.Wikipedia.org/wiki/Coordinate_System

#Mathematics #Computer Graphics

Trending Blogs

Recently Viewed Blogs

COMPUTERSCIENCE-NOTES