What is software process? What are the 4 activities of software process framework?

Software Process: 

Software Process is a set of required activities and the outcome of the activities with a target to produce a software product. A software process is a flowchart of developing a software product, which includes fathering requirements, analyzing those requirements, scheduling development phases, checking the developments, implementing changes etc. and this can be till the delivery of the final software product to the after delivery service methods and more.

What are the types of software products?

Types of Software Product: Based on how and why the software products are being developed, software products can be of the following two types

What are the conditions for deadlock situation to occur?


In a system, deadlock situations are moments when processes never finish executing and system resources are tied up, which ultimately prevents other processes from ever starting. Dead lock situations are obviously undesirable, however they occur in systems while the following conditions take place simultaneously. These conditions are not completely independent, that is, all four conditions must hold for a deadlock to occur.

Explain an example of Dry Cell or Short note on Leclanche cell.

Example of Dry Cell - Leclanche Cell:

The most common example of dry cell is Leclanche cell invented by French scientist Georges Leclanche. We use to call it a battery. It has a cylindrical Zn container which works as the anode. At the center of the Zn container a carbon or graphite rod is placed vertically in a mixture of MnO2 and graphite powder. The Zn container is then filled up with a paste of ZnCl2 and NH4Cl. The above described Leclanche cell may be represented as follows,

What is chemical bond? What are different types of chemical bonds?

Chemical bond

Atoms of all elements except of the inert gasses have a tendency to combine either with each other or with the atoms of other elements to form cluster of atoms with definite composition. A cluster formed may be either a molecule or an ion. The attraction between the atoms forming the cluster is called a chemical bond.

Nature of bonding and properties of certain solids.


Diamond is an allotrope of carbon. Due to difference in bonding in its structure, it looks quite different from the other allotropes. Each carbon atom of diamond is sp3 hybridized. The four sp3 orbital arrange themselves in the four corners of a tetrahedron. Each orbital forms a bond with an orbital of another carbon atom. So, in diamond, each carbon atom surrounded by four carbon atoms arranged tetrahedral forming a giant three dimensional molecule. All the electrons in the outer most shell of each carbon atom is engaged in covalent formation. So, no free electron is found, which makes diamond a non-conductor of electricity. It is also transparent to X-ray and white light as there are no free electrons to encounter with X-ray or white light. Due to its firm rigid arrangement of the carbon atom, with bond distance of 1.54 A, diamond is the hardest substance found in naturally.

Also it needs a high amount of energy to break the bonds between the carbon atoms to turn it into liquid. So its melting point is very high (3500°C) and its density is 3.5.

Briefly explain the formation of dimmers and trimmers.

Some compounds like hydrogen fluorides, ethanoic acids, benzoic acid form dimmers or trimmers by joining up of their two or three molecules by H-bonding. Sometime, due to the formation of these dimmers or trimmers the molecular weight of these compounds appears to be doubled or tripled. That is, ethanoic acid has molecular weight of 60, but in a dimmer of this molecule the molecular weight appears to be 120.

Briefly explain Atomic spectra and Hydrogen Spectra.

Atomic spectra:

When a ray of light is passed through a glass prism, it is dispersed into a band of seven colors. This is called a spectrum. 

When a gas or vapor is heated to a high temperature or subjected to electric discharge, it emits light of all wavelengths. This light, if passed through a prism, a spectrum is formed having single lines or band lines at definite positions and the lines have definite frequencies also. The line spectra are also formed by atoms and are called atomic spectra. The band spectra are actually a collection of many lines formed by a molecule and is also called a molecular spectrum. Line spectra are characteristic properties of elements. 

What is a process in operating system? What are the process states?


A process can be thought as a program in execution, but a program by itself is not a process. Process is nothing but a set of instruction to be executed. Multiple instances of a single process can be running at any given time and also a process may create sub-processes with time. Processes may need certain resources like, CPU time, memory, files and access to other devices.

Reasons for building Distributed Systems.

Distributed Systems: 

Distributed Systems (also loosely coupled systems) are also multiprocessor systems but they will not be sharing clock, memory etc. and will be communicating with each other with high speed buses, telephone lines etc. Processors in distributed systems may vary in size and function and include microprocessors, workstations to large general-purpose computers. Some of the reasons for building distributed systems are resource sharing, computation speed up, reliability, communication etc.

Briefly describe different types of operating systems.

Operating systems and computer architecture have had a great influence on each other. As hardware industry started to develop powerful and feature enriched hardware for computers, the operating systems needed to update themselves to harness the power of those hardware. Again, as operating systems started to show what else they can do, hardware manufacturers needed to develop further better hardware. Following is a list of operating systems.

What is operating system? Describe operating systems in brief.

Operating System: An operating system is an intermediary program between computer user and the computer hardware. This computer user can also be just another software running on the operating system or another computer or device. So basically, operating systems are computer programs that let other computer programs or humans communicate with the hardware of the computers. 

What is histogram? How low brightness and high brightness images can be identified from a histogram? DIP


The histogram plots the number of pixels in the image (vertical axis) with a particular brightness value (horizontal axis). Considering the following graph,

Brightness and Contrast in Digital Image Processing.

Brightness: Brightness of an image is defined by the higher grey-scale values. Such as, if an image has grey-scale values like 175,200,255 etc, it can be said that brightness of the image is high. That is, the higher the grey-scale value the higher the brightness of an image. Thus brightness of an image is the higher values of the grey-scale levels.

Describe the high pass filter. DIP

High Pass Filter: Considering the grey-scale values of a part of an image as below,
Here, we have taken 9 grey scale values. It is seen that the 5th value is very different than the other 8 values, that is a big change is occurring at that point due to the big change of the grey-scale value at that point than the other points. 

Describe the median pass filter. DIP

Median Filter: Median filter, as the name implies, replaces the center value of a mask with the median of all the values of the mask. Simply taking some grey-scale values of an image and taking a 3×3 mask. Now we have 9 values and the 5th value is the median. Thus, the center value of the mask will be replaced by the median. So, the implementation of this filter is as follows,

All questions in Class Notes - Database Management System

Following is a list of all the question in the section Class Notes: Database Management System. When new class notes will be added, links of those posts will be added to this list too.

Draw the database system architecture. DBMS

Following is a flowchart drawing of Database system architecture.

Who is Database administrator? Write some functions of DBA in DBMS

Database Administrator: One of the main reasons behind using DBMS is to have central control on both data and the applications access those data. The person who has such central control over the data is called a database administrator (DBA). Some of the functions of DBA are given below,

Describe different types of database users and their interfaces. DBMS

There are about 4 different types of database users differentiated by their way of interaction with the database system. Brief description has been given below,

What is transaction? What is Transaction Management? DBMS

Transaction: A transaction is a collection of operations that performs a single logical function in a database application. Such as, when we want to add BDT 500 to account A and subtract BDT 500 from account B, that will be a transaction. 

Briefly describe the two-tier and three-tier architecture. DBMS

Two-tier Architecture: In the two-tier architecture, the application is partitioned into a component that resides at the client machine and calls the database system functionality at the server machine using query language statements. Application program interface standards like ODBC and JDBC are used for interaction between the client and the server. 

Describe the components of the query processor. DBMS

Query Processor: As query is very much necessary to find out only the data user need from tons of data of the database, query processor is very important to process these query requests. Query processors come with the following components,

Describe the data structures implemented by the storage manager.

Data Structures Implemented by the Storage Manager: The storage manager implements several data structures as part of the physical system implementation.

What is storage manager? Describe the components of storage manager. DBMS

Storage Manager: A storage manager is a program module which is responsible for storing, retrieving and updating data in the database. 

In how many ways can database constraints be tested/evaluated? Describe briefly. DBMS

Database Constraints: Database constraints are like conditions given to the manipulation of values of a field or attribute. Such as, we may limit the values under the payment attribute of a table that its value can never be less than BDT 350. Constraints can be tested as follows,

Describe Data Definition Language (DDL). DBMS

Data Definition Language (DDL): The specific language used to express the database schema by a set definitions is called Data Definition Language (DDL). The DDL is also used to specify additional properties of the data. Another special type of DDL, called the Data Storage and Definition Language, is used to specify storage and data access methods.

What are database languages? Describe DML (DBMS)

Database Language: As whatever we want to be manipulated by computer has to be written using specific language, database is not beyond them. To write or create database management system we use database languages. They are of two types; Data Definition Language (DDL) and Data Manipulation Language (DML). DDL is used to design a database and DML is used express database’s queries and updates.

What is data model? Describe various data models. DBMS

Data Model: Data model is the structure of the database, which is a collection of conceptual tools for describing data, data relationships, data semantics and consistency constraints. 

What are instances and schema? DBMS

Instances: A database is generally used by many users where insertion and deletion of data occurs frequently. Overall information stored in a database at a particular moment is called the instance of the database. 

What is data abstraction? Describe the levels briefly. DBMS

Data Abstraction: Different users require different view of the database which is useful and necessary to them. This is data abstraction by which we abstract useful data from a database for a particular type of users to use. 

Briefly describe the disadvantages of file processing system? DBMS

Disadvantages of File Processing System: Keeping organization information in a file processing system has some disadvantages including the followings,

What are the applications of DBMS?

Applications of DBMS: DBMS is getting used in many places. Everything from file cabinets to dictionaries is disappearing from today’s working place, because it is easy to make use of the data using a DBMS. The uses or applications of DBMS include the following,

What is Database? Define DBMS (Database Management System).

Database: A database contains a collection of related items or facts arranged in a specific structure. The most obvious example of a non-computerized database is a telephone directory. 

How to double-click & run PHP in CMD/console?

Hello everyone,

Welcome to this short tutorial on how to run PHP codes in console or CMD.

You get PHP console with your PHP setup called php.exe which generally resides in your PHP folder. I have WAMP installed in my computer so I have PHP installed via WAMP.