Unit: 1 – Computing Devices, Software and Operating System Level: BBA 1st Semester
Subject: Computer & It Application
(For Pokhara University)
Section B: Descriptive answer questions.
1. Draw a block diagram of a simple digital computer and explain the function of each block briefly.
Computer system is an integrated work of input unit, Central processing unit (CPU) and Output unit. Row data given by input is processed by central processing unit and the required. Output (information) is provided by output unit. The components of digital computer system are:
i. Input unit: An input unit tells input and converts it into binary form so that the computer can understand it. It is formed by input devices e.g.: keyboard, mouse, light-pen etc.
ii. Central processing unit: The brain of computer execute programs and control the operation of other units. The components of CPU are:
Memoryunit (MU) or register: It is primary storage and temporarily stores incoming data, intermediate data and the final result of processing. It also stores instruction for a job.
- Arithematic and logical unit (ALU): ALU performs mathematical calculation such as addition, subtraction, multiplication, division (+, -, *, /) and logical operation such as greater than, less than, equal than or equal, not equal, greater or equal (<,>,=,<=,>=,<>), AND, OR. The result of
logicaloperation is TRUE ofFalse.
- Control unit: The control unit (CU) controls and guides the instruction flow and manipulation of all data’s and information. CU sends control signals until the required operations are done property by ALU and memory. It is responsible for timing and
queingfor data and instruction. CU gives commandto transfer data from the input devices, MU, ALU, memory and out device.
CPU = ALU + CU + MU
iii. Output: The outcome of CPU is in the form of electronic binary signals which is converted by output unit so that they can be understood by human being. Monitor, printer, plotter, speller, etc are the example of output unit devices.
iii. Secondary storage: Due to
2. Add two binary numbers (1010011)2 and convert the sum result into hexadecimal format.
= (101001)2 + (110111)2 = (10001010)2
1×27 + 0×26 + 0×25 + 0×24 + 0×23 + 0×22 + 0×21 + 0×20 = decimal value.
(10001010)2 = (138)10
8 10 ⇒ (8A)16
(10001010)2 = (138)10 = (8A)16
3. What is operating system? Why is it necessary in computer? Is the computer system possible without it?
Ans: Operating System
An operating system is an organized set or collection of software programs that control the overall operation of the computer system. OS is an interface between hardware and user which is responsible for the management and co-ordination of activities and the sharing of resources of the computer that acts as a host for computing applications run on the machine. E.g. Windows, MS-DOS, Linux, AIX etc.
It is necessary in computer because without it, computer is simply an object with no response. the application program makes the use of operating system by making request for services through a defined application program interface. Due to the presence of OS, an operator (user) does not have to know all the technical details and functional aspects of the hardware.
The computer system is not possible without it as all the operation and function of hardware are interact by user through operating system. All human are not able to interact directly to machine (hardware) as the technical and logical aspects are complex.
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4. Explain the function of the following commands with syntax (any four).
i. MKDIR ii. DIR/W/P/S iii. Ver iv. Edit v. Scandisk
Creates a directory.
Syntax: MKDIR [drive] path.
e.g: C:\>MKDIR Test :- Creates test directory in C drive.
C:\>MKDIR \BBA\ab1 :- Creates subdirectory lab1 in the directory BBA in C drive.
DIR: Displays a list of files and subdirectories in a directory.
Syntax: DIR [drive:] [path] [filename] [/A:[Attributes]] [/B] [/C] [/L]
[/O:[order]] [/S] [/P] [/W] [/Q]
[Drive:] [path] [filename]: drive, directory and files to display.
/P: pause after each screenful information.
/W: display the list of files in a wide formal.
/S: displays files in specified directory and sub directories.
It is internal command. Displays the MS DOS version in use.
- External command
- It is used to compile, edit, save, copy and print straight forward and simple text.
Syntax: EDIT [drive:] [path] filename
e.g. C:\> Edit CONFIG.SYS
- External command.
- It repairs the disks. It checks the surface of disks.
Syntax: Scandisk [drive:] [/All] [/CHECKONLY] [/AUTOFIX] [/NOSAVE] [/SURFACE]
To check and repair the disk at current drive.
5. Define different kinds of network topologies used in computer networking.
- Bus Topology
A bis topology uses one long cable (backbone) to which network devices (computer or a ) are directly attached or attached by using short drop cable. As all computers share this bus, a computer checks for any information that might be coming down the backbone before sending its message. A message passes the other computers on the way to computers destination.
Each computer then checks the address of each the to see if it matches its own. They don’t move data affect the rest of the networks. Backbone must be terminated at both ends to prevent echoing back of signal.
- Ring Topology
Ring Topology consists of several computers joined together to form a circle. Messages move from one computer to the next in one direction only. When a computer receives a message addressed to it, the message is copied and sent back with modification to indicate that it was received. Computers connected to a ring topology are responsible for moving data from themselves to the next computer. Thus, if one computer fails, it affects the rest of the network.
- Star Topology
In star topology, each device (computer) has a dedicated point to point to point link only to a central controller, usually called a hub. The computers are not directly linked to one another. Unlike other topology, start topology does not allow direct traffic (flow of data) between computers. The controller acts as an exchange. If one link fails, only that link is affected and all other links are active.
- Mesh Topology
In mesh topology, each computer has a dedicated point to point link to other computers. The term dedicated means that the link carries traffic only between the two devices. Hence, a fully connected topology of n computers has n(n-1)/2 links. If one link fails, it does not affect entire system. It has privacy or security. Large amount of cable is required.
- Solved Notes – Unit: 1 – Computing Devices, Software & Operating System | BBA 1st Semester | Computer & IT Application
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