IT Assignment BCA (NOU)

01. Why memory required in computer? Define memory hierarchy..

Memory is needed to store data and retrieve it when needed. Computers have two kind of memory, one is primary and another is secondary. Secondary memory is commonly known as just storage. It's used to store files when they are not needed by the processors.

Memory hierarchy is a concept that is necessary for the CPU to be able to manipulate data.

Computer memory is classified in the below hierarchy.

1 . Internal register is for holding the temporary results and variables. Accessing data from these registers is the fastest way of accessing memory.

2. Cache is used by the CPU for memory which is being accessed over and over again. Instead of pulling it every time from the main memory, it is put in cache for fast access. It is also a smaller memory, however, larger than internal register.

3) Main memory or RAM (Random Access Memory): It is a type of the computer memory and is a hardware component. It can be increased provided the operating system can handle it.

4) Hard disk: A hard disk is a hardware component in a computer. Data is kept permanently in this memory. Memory from hard disk is not directly accessed by the CPU, hence it is slower. As compared with RAM, hard disk is cheaper per bit.

5) Magnetic tape: Magnetic tape memory is usually used for backing up large data. When the system needs to access a tape, it is first mounted to access the data. When the data is accessed, it is then unmounted. The memory access time is slower in magnetic tape and it usually takes few minutes to access a tape.

02. What is computer network? Discuss various LAN topologies with the help of an example of each type.

A computer network is a digital telecommunications network which allows nodes to share resources. In computer networks, computing devices exchange data with each other using connections (data links) between nodes. These data links are established over cable media such as wires or optic cables, or wireless media such as Wi-Fi.

Types of Network Topologies:
The mapping of a LAN design is called Topology. There are four categories: Star topology, Bus topology, Ring topology and Mesh topology. Hybrid combinations of these topologies also exist.

Star topology – all computers and devices are connected to a main hub or switch. The hub or switch amasses and disburses the flow of data within the network. Star topology is the most common type of network and f ollows the Ethernet standard.

Bus topology – In this arrangement computers and devices are connected to a single linear cable called a trunk. The trunk is also referred to as the backbone or a segment. Each end of the trunk must be discharged to prevent the signal from rebounding back up the cable.

Ring topology – computers and devices are connected to a closed loop cable. Here there are no terminating ends so if one system crashes the entire network goes down. Each computer functions as a repeater and charges the signal before sending it to the next station.

In Ring topology data is sent through the network by way of a token. If the token isn’t carrying any data, a computer waiting to send data seizes it, attaches the data and the electronic address to the token and sends it on. Once the token is received by the destination computer it strips the data and the token is sent on. This is why it’s named a token ring network.