Bangladesh karmachari Kallyan Board- Assistant Programmer, 2017

Bangladesh karmachari Kallyan Board- Assistant Programmer, 2017

1.   What is computer bus? What is the unit of measurement of speed of computer bus? Describe various types of computer bus.

The electrically conducting path along which data is transmitted inside any digital electronic device. A Computer bus consists of a set of parallel conductors, which may be conventional wires, copper tracks on a PRINTED CIRCUIT BOARD, or microscopic aluminum trails on the surface of a silicon chip. Each wire carries just one bit, so the number of wires determines the largest data WORD the bus can transmit: a bus with eight wires can carry only 8-bit data words, and hence defines the device as an 8-bit device.

speeds are expressed in megahertz MHz or gigahertz GHz. Mega means million and hertz means times per second, 200 MHz is 200 million times per second (and 200 GHz is 200 billion times per second).

Types of Computer Bus

There are a variety of buses found inside the computer.

Data Bus: The data bus allows data to travel back and forth between the microprocessor (CPU) and memory (RAM).

Address Bus: The address bus carries information about the location of data in memory.

Control Bus : The control bus carries the control signals that make sure everything is flowing smoothly from place to place.

 

2.   What is an operating system? Write 4 functions of operating system?

An Operating System (OS) is an interface between a computer user and computer hardware. An operating system is a software which performs all the basic tasks like file management, memory management, process management, handling input and output, and controlling peripheral devices such as disk drives and printers.

1.     Security –The operating system uses password protection to protect user data and similar other techniques. it also prevents unauthorized access to programs and user data.

2.     Control over system performance –Monitors overall system health to help improve performance. records the response time between service requests and system response to have a complete view of the system health. This can help improve performance by providing important information needed to troubleshoot problems.

3.     Job accounting –Operating system Keeps track of time and resources used by various tasks and users, this information can be used to track resource usage for a particular user or group of user.

4.     Error detecting aids –Operating system constantly monitors the system to detect errors and avoid the malfunctioning of computer system.

5. Coordination between other software and users –
   Operating systems also coordinate and assign interpreters, compilers, assemblers and other software to the various users of the computer systems.
6. Memory Management –
   The operating system manages the Primary Memory or Main Memory. Main memory is made up of a large array of bytes or words where each byte or word is assigned a certain address. Main memory is a fast storage and it can be accessed directly by the CPU. For a program to be executed, it should be first loaded in the main memory.
7. Processor Management –In a multi programming environment, the OS decides the order in which processes have access to the processor, and how much processing time each process has. This function of OS is called process scheduling.
8. Device Management –An OS manages device communication via their respective drivers. It performs the following activities for device management. Keeps tracks of all devices connected to system.
9. File Management - A file system is organized into directories for efficient or easy navigation and usage. These directories may contain other directories and other files.

 

3.   What is a computer virus? Write the name of 6 anti-virus in computers?

A computer virus is a type of computer program that, when executed, replicates itself by modifying other computer programs and inserting its own code. When this replication succeeds, the affected areas are then said to be "infected" with a computer virus.

name of 6 anti-virus in computers

Norton Antivirus

REVE Antivirus

Avira Antivirus

AVG Antivirus

Kaspersky Lab Internet Security

McAfee Antivirus

4.   What is computer network? Write the name of 4 networking topology.

A computer network is a system in which multiple computers are connected to each other to share information and resources.

BUS Topology

Bus topology is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is called Linear Bus topology.

Advantages of Bus Topology

It is cost effective.

Cable required is least compared to other network topology.

Used in small networks.

It is easy to understand.

Easy to expand joining two cables together.

Disadvantages of Bus Topology

Cables fails then whole network fails.

If network traffic is heavy or nodes are more the performance of the network decreases.

Cable has a limited length.

It is slower than the ring topology.

RING Topology

It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbours for each device.

Advantages of Ring Topology

Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data.

Cheap to install and expand

Disadvantages of Ring Topology

Troubleshooting is difficult in ring topology.

Adding or deleting the computers disturbs the network activity.

Failure of one computer disturbs the whole network.

STAR Topology

In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.

Advantages of Star Topology

Fast performance with few nodes and low network traffic.

Hub can be upgraded easily.

Easy to troubleshoot.

Easy to setup and modify.

Only that node is affected which has failed, rest of the nodes can work smoothly.

Disadvantages of Star Topology

Cost of installation is high.

Expensive to use.

If the hub fails then the whole network is stopped because all the nodes depend on the hub.

Performance is based on the hub that is it depends on its capacity

MESH Topology

It is a point-to-point connection to other nodes or devices. All the network nodes are connected to each other. Mesh has n(n-1)/2 physical channels to link n devices.

Advantages of Mesh Topology

Each connection can carry its own data load.

It is robust.

Fault is diagnosed easily.

Provides security and privacy.

Disadvantages of Mesh Topology

Installation and configuration is difficult.

Cabling cost is more.

Bulk wiring is required.

TREE Topology

It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy.

Advantages of Tree Topology

Extension of bus and star topologies.

Expansion of nodes is possible and easy.

Easily managed and maintained.

Error detection is easily done.

Disadvantages of Tree Topology

Heavily cabled.

Costly.

If more nodes are added maintenance is difficult.

Central hub fails, network fails.

HYBRID Topology

It is two different types of topologies which is a mixture of two or more topologies. For example if in an office in one department ring topology is used and in another star topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology).

Advantages of Hybrid Topology

Reliable as Error detecting and trouble shooting is easy.

Effective.

Scalable as size can be increased easily.

Flexible.

Disadvantages of Hybrid Topology

Complex in design.

Costly.

5.   What is Database? What is DBMS? Write the full meaning of DDL and DML?

A database is an organized collection of data, generally stored and accessed electronically from a computer system. Where databases are more complex they are often developed using formal design and modeling techniques.

A database management system (DBMS) is system software for creating and managing databases. A DBMS makes it possible for end users to create, read, update and delete data in a database. The most prevalent type of data management platform, the DBMS essentially serves as an interface between databases and end users or application programs, ensuring that data is consistently organized and remains easily accessible.

DDL

DDL is Data Definition Language and is used to define the structures like schema, database, tables, constraints etc. Examples of DDL are create and alter statements.

DML

DDL is Data Manipulation Language and is used to manipulate data. Examples of DML are insert, update and delete statements.

       

6.   Differentiate between cache memory and virtual memory?    

Difference between Virtual memory and Cache memory:

S.NO	VIRTUAL MEMORY	CACHE MEMORY
1.	Virtual memory increases the capacity of main memory.	While cache memory increase the accessing speed of CPU.
2.	Virtual memory is not a memory unit, its a technique.	Cache memory is exactly a memory unit.
3.	The size of virtual memory is greater than the cache memory.	While the size of cache memory is less than the virtual memory.
4.	Operating System manages the Virtual memory.	On the other hand hardware manages the cache memory.
5.	In virtual memory, The program with size larger than the main memory are executed.	While in cache memory, recently used data is copied into.
6.	In virtual memory, mapping frameworks is needed for mapping virtual address to physical address.	While in cache memory, no such mapping frameworks is needed.

 

8.   What is data communication? Describe about 3 modes of data communication?

Data communication refers to the exchange of data between a source and a receiver via form of transmission media such as a wire cable. Data communication is said to be local if communicating devices are in the same building or a similarly restricted geographical area.

Comparison Chart

Basis for Comparison	Simplex	Half Duplex	Full Duplex
Direction of Communication	Unidirectional	Two-directional, one at a time	Two-directional, simultaneously
Send / Receive	Sender can only send data	Sender can send and receive data, but one a time	Sender can send and receive data simultaneously
Performance	Worst performing mode of transmission	Better than Simplex	Best performing mode of transmission
Example	Keyboard and monitor	Walkie-talkie	Telephone

 

8.      Give the full form of: VGA, OCR, LAN, VLAN, SMTP, ICMP, URL, VOIP, VSAT, TCP/IP, and DHCP.

Video Graphics Array (VGA) 

Optical character recognition

Local Area Network

Virtual Local Area Network

SMTP Simple Mail transfer Protocol

Internet Control Message Protocol

Uniform Resource Locator (URL)

Voice over Internet Protocol

Dynamic Host Configuration Protocol (DHCP)

very-small-aperture terminal (VSAT)