Fundamentals of Computer – Semester II - SAMUNDRAGYAAN EDUCATION FOUNDATION

MOST REPEATED QUESTIONS

SEMESTER – 2 EXAM

Q.1 What is Computer ? Explain different types of Computer ?

A computer is a programmable electronic device that accepts raw data as input and processes it with a set of instructions (a program) to produce the result as output. It renders output just after performing mathematical and logical operations and can save the output for future use. It can process numerical as well as non-numerical calculations. The term “computer” is derived from the Latin word “computare” which means to calculate.
A computer is designed to execute applications and provides a variety of solutions through integrated hardware and software components. It works with the help of programs and represents the decimal numbers through a string of binary digits. It also has a memory that stores the data, programs, and result of processing. The components of a computer such as machinery that includes wires, transistors, circuits, hard disk are called hardware. Whereas, the programs and data are called software.
It is believed that the Analytical Engine was the first computer which was invented by Charles Babbage in 1837. It used punch cards as read-only memory. Charles Babbage is also known as the father of the computer.

The basic parts without which a computer cannot work are as follows

Processor: It executes instructions from software and hardware.
Memory: It is the primary memory for data transfer between the CPU and storage.
Motherboard: It is the part that connects all other parts or components of a computer.
Storage Device: It permanently stores the data, e.g., hard drive.
Input Device: It allows you to communicate with the computer or to input data, e.g., a keyboard.
Output Device: It enables you to see the output, e.g., monitor.

Computers are divided into different types based on different criteria. So, on the basis of size, there are five types of computers:

Supercomputer
Mainframe computer
Minicomputer
Workstation
PC (Personal Computer)

And on the basis of data handling capabilities, there are three types of computer:

Analogue Computer
Digital Computer
Hybrid Computer

1. Supercomputer:

When we talk about speed, then the first name that comes to mind when thinking of computers is supercomputers. They are the biggest and fastest computers(in terms of speed of processing data). Supercomputers are designed such that they can process a huge amount of data, like processing trillions of instructions or data just in a second. This is because of the thousands of interconnected processors in supercomputers. It is basically used in scientific and engineering applications such as weather forecasting, scientific simulations, and nuclear energy research. It was first developed by Roger Cray in 1976.

Characteristics of supercomputers:

Supercomputers are the computers which are the fastest and they are also very expensive.
It can calculate up to ten trillion individual calculations per second, this is also the reason which makes it even more faster.
It is used in the stock market or big organizations for managing the online currency world such as bitcoin etc.
It is used in scientific research areas for analyzing data obtained from exploring the solar system, satellites, etc.

2. Mainframe computer:

Mainframe computers are designed in such a way that it can support hundreds or thousands of users at the same time. It also supports multiple programs simultaneously. So, they can execute different processes simultaneously. All these features make the mainframe computer ideal for big organizations like banking, telecom sectors, etc., which process a high volume of data in general.

Characteristics of mainframe computers:

It is also an expensive or costly computer.
It has high storage capacity and great performance.
It can process a huge amount of data (like data involved in the banking sector) very quickly.
It runs smoothly for a long time and has a long life.

3. Minicomputer:

Minicomputer is a medium size multiprocessing computer. In this type of computer, there are two or more processors, and it supports 4 to 200 users at one time. Minicomputers are used in places like institutes or departments for different work like billing, accounting, inventory management etc. It is smaller than a mainframe computer but larger in comparison to the microcomputer.

Characteristics of minicomputer:

Its weight is low.
Because of its low weight, it is easy to carry anywhere.
less expensive than a mainframe computer.
It is fast.

4. Workstation:

Workstation is designed for technical or scientific applications. It consists of a fast microprocessor, with a large amount of RAM and high speed graphic adapter. It is a single-user computer. It generally used to perform a specific task with great accuracy.

Characteristics of Workstation:

It is expensive or high in cost.
They are exclusively made for complex work purposes.
It provides large storage capacity, with better graphics, and a more powerful CPU when compared to a PC.
It is also used to handle animation, data analysis, CAD, audio and video creation, and editing.

5. PC (Personal Computer):

It is also known as a microcomputer. It is basically a general-purpose computer and designed for individual use. It consists of a microprocessor as a central processing unit(CPU), memory, input unit, and output unit. This kind of computer is suitable for personal work such as making an assignment, watching a movie, or at office for office work, etc. For example, Laptops and desktop computers.

Characteristics of PC (Personal Computer):

In this limited number of software can be used.
It is smallest in size.
It is designed for personal use.
It is easy to use.

6. Analogue Computer:

It is particularly designed to process analogue data. Continuous data that changes continuously and cannot have discrete values is called analogue data. So, an analogue computer is used where we don’t need exact values or need approximate values such as speed, temperature, pressure etc. It can directly accept the data from the measuring device without first converting it into numbers and codes. It measures the continuous changes in physical quantity. It gives output as a reading on a dial or scale. For example speedometer, mercury thermometer, etc.

7. Digital Computer:

Digital computers are designed in such a way that it can easily perform calculations and logical operations at high speed. It takes raw data as an input and processes it with programs stored in its memory to produce the final output. It only understands the binary input 0 and 1, so the raw input data is converted to 0 and 1 by the computer and then it is processed by the computer to produce the result or final output. All modern computers, like laptops, desktops including smartphones are digital computers.

8. Hybrid Computer:

As the name suggests hybrid, which means made by combining two different things. Similarly, the hybrid computer is a combination of both analog and digital computers. Hybrid computers are fast like an analog computer and have memory, and accuracy like a digital computer. So, it has the ability to process both continuous and discrete data. For working when it accepts analog signals as input then it converts them into digital form before processing the input data. So, it is widely used in specialized applications where both analog and digital data is required to be processed. A processor which is used in petrol pumps that converts the measurements of fuel flow into quantity and price is an example of a hybrid computer.

Q.2 Define Hardware and Software ? Write the difference between system software and Application Software ?

A computer system is divided into two categories: Hardware and Software. Hardware refers to the physical and visible components of the system such as a monitor, CPU, keyboard and mouse. Software, on the other hand, refers to a set of instructions which enable the hardware to perform a specific set of tasks. The software must be installed in the hardware to function properly and similarly, the hardware must be present for the tasks to be performed. Both are interdependent, yet they are also different from each other.

Hardware refers to the physical components of a computer. Computer Hardware is any part of the computer that we can touch these parts. These are the primary electronic devices used to build up the computer. Examples of hardware in a computer are the Processor, Memory Devices, Monitor, Printer, Keyboard, Mouse, and Central Processing Unit.

Hardware	Software
Hardware is further divided into four main categories: Input Devices Output Devices Secondary Storage Devices Internal Components	Software is further divided into two main categories: Application Software System Software
Developed using electronic and other materials	Developed writing using instructions using a programming language
When damaged, it can be replaced with a new component	When damaged it can be installed once more using a backup copy
Hardware is physical in nature and hence one can touch and see hardware	The software cannot be physically touched but still can be used and seen
Hardware cannot be infected by Viruses	The software can be infected by Viruses
Hardware will physically wear out over time	Software does not wear out but it can be affected by bugs and glitches
An example of Hardware is hard drives, monitors, CPU, scanners, printers etc.	An example of software is Windows 10, Adobe Photoshop, Google Chrome etc

Types of Computer Hardware

Input Devices
Output Devices
Storage Devices
Internal Component

1. Input Devices: Input Devices are those devices through which a user enters data and information into the Computer or simply, User interacts with the Computer. Examples of Input Devices are Keyboard, Mouse, Scanner, etc.

2. Output Devices: Output Devices are devices that are used to show the result of the task performed by the user. Examples of Output Devices are Monitors, Printers, Speakers, etc.

3. Storage Devices: Storage Devices are devices that are used for storing data and they are also known as Secondary Storage Data. Examples of Storage Devices are CDs, DVDs, Hard Disk, etc

4. Internal Component: Internal Components consists of important hardware devices present in the System. Examples of Internal Components are the CPU, Motherboard, etc.

Computer Software

Software is a collection of instructions, procedures, and documentation that performs different tasks on a computer system. we can say also Computer Software is a programming code executed on a computer processor. The code can be machine-level code or code written for an operating system. Examples of software are MS- Word, Excel, PowerPoint, Google Chrome, Photoshop, MySQL, etc.

Types of Computer Software

System Software
Application Software

1. System Software: System Software is a component of Computer Software that directly operates with Computer Hardware which has the work to control the Computer’s Internal Functioning and also takes responsibility for controlling Hardware Devices such as Printers, Storage Devices, etc. Types of System Software include Operating systems, Language processors, and Device Drivers.

2. Application Software: Application Software are the software that works the basic operations of the computer. It performs a specific task for users. Application Software basically includes Word Processors, Spreadsheets, etc. Types of Application software include General Purpose Software, Customized Software, etc.

System Software vs Application Software – Comparative Analysis

As discussed earlier, there are various points of difference between a system and application software. The same has been given in a tabulated manner below for an easy and better understanding of the two.

Difference Between System Software and Application Software
System Software	Application Software
This acts as an interface between the system and the applications	This is designed directly from the user perspective
It is the platform that allows the various application software to run on the system	These are independent applications which can be download and installed in the system
System Software is generally developed in low-level languages. This is so that the interaction between the software and hardware can be simplified and made more compatible	Each application has a specific purpose and thus is developed with high-level languages so that the purpose can be fulfilled
Is working is more automated. Once a system is turned on, the system software starts working	User action is required to start application software. These applications can only be work when the user commands the system to do so
These are responsible for the working of the system	They have minimum involvement in the processing and functioning of the computer device
The system software are installed at the time of installing the operating system. A computer device cannot work without its presence	The application software can be installed as and when the user requires them
It is an independent software. Once this is installed the computer will work	This is a dependent software. Applications can only be downloaded when the operating system is installed
Since a device cannot work without a system software, the user has to have it installed in their devices	These are designed to be user interactive, thus the application software can be removed as and when required by the user
Example for System Software includes Android, Mac Operating system, MS Windows, etc.	Examples of Application Software includes Word Processor, games, media player, etc.

Q.3 What is Operating System ? Explain different types of Operating System and features of OS ?

Operating System lies in the category of system software. It basically manages all the resources of the computer. An operating system acts as an interface between the software and different parts of the computer or the computer hardware. The operating system is designed in such a way that it can manage the overall resources and operations of the computer. It is a fully integrated set of specialized programs that handle all the operations of the computer. It controls and monitors the execution of all other programs that reside in the computer, which also includes application programs and other system software of the computer.

Examples of operating system are Windows, Linux, Mac OS, etc.

An operating system (OS) is a collection of software that manages computer hardware resources and provides common services for computer programs. The operating system is the most important type of system software in a computer system.

History of Operating Systems

The first computer, Z1, was made in 1936 – 1938. Unfortunately, this computer ran without an operating system.
Twenty years later, the first-ever operating system was made in 1956.
In the 1960s, bell labs started working on building UNIX, the first multitasking operating system.
In 1977 the apple series came into existence. Apple Dos 3.3 was the first disk operating system.
In 1981, Microsoft built the first operating system called DOS by purchasing 86 – DOS software from a Seattle company.
The most famous Microsoft windows came into existence in 1985 when MS-DOS was paired with GUI, a graphics environment.

The primary functions of an operating system include:

Resource management: The operating system manages and allocates memory, CPU time, and other hardware resources among the various programs and processes running on the computer.
Process management: The operating system is responsible for starting, stopping, and managing processes and programs. It also controls the scheduling of processes and allocates resources to them.
Memory management: The operating system manages the computer’s primary memory and provides mechanisms for optimizing memory usage.
Security: The operating system provides a secure environment for the user, applications, and data by implementing security policies and mechanisms such as access controls and encryption.
File management: The operating system is responsible for organizing and managing the file system, including the creation, deletion, and manipulation of files and directories.
Device management: The operating system manages input/output devices such as printers, keyboards, mice, and displays. It provides the necessary drivers and interfaces to enable communication between the devices and the computer.
Networking: The operating system provides networking capabilities such as establishing and managing network connections, handling network protocols, and sharing resources such as printers and files over a network.
User interface: The operating system provides a user interface that enables users to interact with the computer system. This can be a graphical user interface (GUI), a command-line interface (CLI), or a combination of both.
Backup and recovery: The operating system provides mechanisms for backing up data and recovering it in case of system failures, errors, or disasters.
Virtualization: The operating system provides virtualization capabilities that allow multiple operating systems or applications to run on a single physical machine. This can enable efficient use of resources and flexibility in managing workloads.
Performance monitoring: The operating system provides tools for monitoring and optimizing system performance, including identifying bottlenecks, optimizing resource usage, and analyzing system logs and metrics.
Time-sharing: The operating system enables multiple users to share a computer system and its resources simultaneously by providing time-sharing mechanisms that allocate resources fairly and efficiently.
System calls: The operating system provides a set of system calls that enable applications to interact with the operating system and access its resources. System calls provide a standardized interface between applications and the operating system, enabling portability and compatibility across different hardware and software platforms.

There are several types of operating systems, including single-user, multi-user, and distributed systems. Some of the most popular operating systems in use today are Microsoft Windows, Apple macOS, and Linux.

Characteristics:

Let us now discuss some of the important characteristic features of operating systems:

Device Management: The operating system keeps track of all the devices. So, it is also called the Input / Output controller that decides which process gets the device, when, and for how much time.
File Management: It allocates and de-allocates the resources and also decides who gets the resource.
Job Accounting: It keeps the track of time and resources used by various jobs or users.
Error-detecting Aids: It contains methods that include the production of dumps, traces, error messages, and other debugging and error-detecting methods.
Memory Management: It keeps track of the primary memory

Types of Operating Systems

An Operating System performs all the basic tasks like managing files, processes, and memory. Thus operating system acts as the manager of all the resources, i.e. resource manager. Thus, the operating system becomes an interface between user and machine.

Types of Operating Systems: Some widely used operating systems are as follows-

1. Batch Operating System –
This type of operating system does not interact with the computer directly. There is an operator which takes similar jobs having the same requirement and group them into batches. It is the responsibility of the operator to sort jobs with similar needs.

Advantages of Batch Operating System:

It is very difficult to guess or know the time required for any job to complete. Processors of the batch systems know how long the job would be when it is in queue
Multiple users can share the batch systems
The idle time for the batch system is very less
It is easy to manage large work repeatedly in batch systems

Disadvantages of Batch Operating System:

The computer operators should be well known with batch systems
Batch systems are hard to debug
It is sometimes costly
The other jobs will have to wait for an unknown time if any job fails

Examples of Batch based Operating System: Payroll System, Bank Statements, etc.

2. Time-Sharing Operating Systems –
Each task is given some time to execute so that all the tasks work smoothly. Each user gets the time of CPU as they use a single system. These systems are also known as Multitasking Systems. The task can be from a single user or different users also. The time that each task gets to execute is called quantum. After this time interval is over OS switches over to the next task.

Advantages of Time-Sharing OS:

Each task gets an equal opportunity
Fewer chances of duplication of software
CPU idle time can be reduced
Resource Sharing: Time-sharing systems allow multiple users to share hardware resources such as the CPU, memory, and peripherals, reducing the cost of hardware and increasing efficiency.
Improved Productivity: Time-sharing allows users to work concurrently, thereby reducing the waiting time for their turn to use the computer. This increased productivity translates to more work getting done in less time.
Improved User Experience: Time-sharing provides an interactive environment that allows users to communicate with the computer in real-time, providing a better user experience than batch processing.

Disadvantages of Time-Sharing OS:

Reliability problem
One must have to take care of the security and integrity of user programs and data
Data communication problem
High Overhead: Time-sharing systems have a higher overhead than other operating systems due to the need for scheduling, context switching, and other overheads that come with supporting multiple users.
Complexity: Time-sharing systems are complex and require advanced software to manage multiple users simultaneously. This complexity increases the chance of bugs and errors.
Security Risks: With multiple users sharing resources, the risk of security breaches increases. Time-sharing systems require careful management of user access, authentication, and authorization to ensure the security of data and software.

Examples of Time-Sharing OSs are: Multics, Unix, etc.

Examples of Time-Sharing OS with explanation:

IBM VM/CMS: IBM VM/CMS is a time-sharing operating system that was first introduced in 1972. It is still in use today, providing a virtual machine environment that allows multiple users to run their own instances of operating systems and applications.
TSO (Time Sharing Option): TSO is a time-sharing operating system that was first introduced in the 1960s by IBM for the IBM System/360 mainframe computer. It allowed multiple users to access the same computer simultaneously, running their own applications.
Windows Terminal Services: Windows Terminal Services is a time-sharing operating system that allows multiple users to access a Windows server remotely. Users can run their own applications and access shared resources, such as printers and network storage, in real-time.

3. Distributed Operating System –
These types of the operating system is a recent advancement in the world of computer technology and are being widely accepted all over the world and, that too, with a great pace. Various autonomous interconnected computers communicate with each other using a shared communication network. Independent systems possess their own memory unit and CPU. These are referred to as loosely coupled systems or distributed systems. These system’s processors differ in size and function. The major benefit of working with these types of the operating system is that it is always possible that one user can access the files or software which are not actually present on his system but some other system connected within this network i.e., remote access is enabled within the devices connected in that network.

Advantages of Distributed Operating System:

Failure of one will not affect the other network communication, as all systems are independent from each other
Electronic mail increases the data exchange speed
Since resources are being shared, computation is highly fast and durable
Load on host computer reduces
These systems are easily scalable as many systems can be easily added to the network
Delay in data processing reduces

Disadvantages of Distributed Operating System:

Failure of the main network will stop the entire communication
To establish distributed systems the language which is used are not well defined yet
These types of systems are not readily available as they are very expensive. Not only that the underlying software is highly complex and not understood well yet

Examples of Distributed Operating System are- LOCUS, etc.

4. Network Operating System –
These systems run on a server and provide the capability to manage data, users, groups, security, applications, and other networking functions. These types of operating systems allow shared access of files, printers, security, applications, and other networking functions over a small private network. One more important aspect of Network Operating Systems is that all the users are well aware of the underlying configuration, of all other users within the network, their individual connections, etc. and that’s why these computers are popularly known as tightly coupled systems.

Advantages of Network Operating System:

Highly stable centralized servers
Security concerns are handled through servers
New technologies and hardware up-gradation are easily integrated into the system
Server access is possible remotely from different locations and types of systems

Disadvantages of Network Operating System:

Servers are costly
User has to depend on a central location for most operations
Maintenance and updates are required regularly

Examples of Network Operating System are: Microsoft Windows Server 2003, Microsoft Windows Server 2008, UNIX, Linux, Mac OS X, Novell NetWare, and BSD, etc.

5. Real-Time Operating System –
These types of OSs serve real-time systems. The time interval required to process and respond to inputs is very small. This time interval is called response time.

Real-time systems are used when there are time requirements that are very strict like missile systems, air traffic control systems, robots, etc.

Two types of Real-Time Operating System which are as follows:

Hard Real-Time Systems:
These OSs are meant for applications where time constraints are very strict and even the shortest possible delay is not acceptable. These systems are built for saving life like automatic parachutes or airbags which are required to be readily available in case of any accident. Virtual memory is rarely found in these systems.
Soft Real-Time Systems:
These OSs are for applications where time-constraint is less strict.

Advantages of RTOS:

Maximum Consumption: Maximum utilization of devices and system, thus more output from all the resources
Task Shifting: The time assigned for shifting tasks in these systems are very less. For example, in older systems, it takes about 10 microseconds in shifting one task to another, and in the latest systems, it takes 3 microseconds.
Focus on Application: Focus on running applications and less importance to applications which are in the queue.
Real-time operating system in the embedded system: Since the size of programs are small, RTOS can also be used in embedded systems like in transport and others.
Error Free: These types of systems are error-free.
Memory Allocation: Memory allocation is best managed in these types of systems.

Disadvantages of RTOS:

Limited Tasks: Very few tasks run at the same time and their concentration is very less on few applications to avoid errors.
Use heavy system resources: Sometimes the system resources are not so good and they are expensive as well.
Complex Algorithms: The algorithms are very complex and difficult for the designer to write on.
Device driver and interrupt signals: It needs specific device drivers and interrupts signals to respond earliest to interrupts.
Thread Priority: It is not good to set thread priority as these systems are very less prone to switching tasks.

Examples of Real-Time Operating Systems are: Scientific experiments, medical imaging systems, industrial control systems, weapon systems, robots, air traffic control systems, etc.

Features of Operating Systems

Here is a list of some important features of operating systems:

Provides a platform for running applications
Handles memory management and CPU scheduling
Provides file system abstraction
Provides networking support
Provides security features
Provides user interface
Provides utilities and system services
Supports application development

Q.4 What is DOS ? Write difference between Internal and External commands in MS – DOS . Write five internal and external commands of DOS ?

Any operating system which runs from the hard disk drive is termed a Disk Operating System ( D.O.S) This also refers to the specific family of disk operating systems known as MS-DOS or Microsoft disk operating system. Anything that commands and controls the computer’s hardware and peripheral devices with control over the program, and its functionality is known as the operating system. This operating system which runs through the hard disk, is known as a disk operating system. For the first time, It was made and introduced for IBM by Microsoft, known as IBM PC DOS, in 1981.

List of DOS

The list of DOS made from 1981 – 1998 are as follows:

IBM PC DOS – 1981
DR-DOS – 1988
ROM-DOS – 1989
PTS-DOS – 1993
FREE-DOS – 1998

It was rebranded version under the title IBM PC DOS, both of which came in the year 1981. DOS other than Microsoft in the market are:

Apple DOS
Apple Pro DOS
Atari DOS
Commodore DOS
TRSDOS
Amiga DOS

It was the first operating system used by IBM-compatible computers. It was first available in two different versions that were typically the same but marketed and controlled under two different brands. MS-DOS was the framework behind Windows operating systems until Windows XP.

“PC-DOS” was the version of dos developed by IBM and sold to the first IBM-compatible manufactured computers. “MS-DOS” was the version of dos that Microsoft bought the rights and patents and was merged with the first versions of Windows. Command-line was used by DOS, or text-based interface, that typed command allowed by the users. By giving simple instructions such as pwd (print working directory) and cd(change directory), the user can open files or run the program or browse the files on the hard drive. Written originally by Tim Patterson (considered the father of DOS) and owned by Seattle Computer Products, Microsoft takes over 86-DOS for $75,000, licensed the same software, and released it with an IBM PC MS-DOS 1.0 in 1982 with IBM and Microsoft joint venture.

MS-DOS was the main operating system for IBM PC compatible personal computers during the 1980s. It was gradually superseded by operating systems offering a graphical user interface (GUI) in various graphical Microsoft Windows operating system generations.

DOS is also used to describe several similar command-line disk operating systems. Early computers, such as the Commodore 64, Atari 800, and Apple II, all featured a disk operating system, including Commodore Business Machines DOS, Atari DOS, and Apple DOS, respectively. DOS/360 was an OS for IBM mainframes, which first appeared in 1966, but it is unrelated to the 8086-based DOS of the 1980s.

How DOS works?

When a computer is powered on, it goes through various steps called the boot process. For a computer running a disk operating system in the following six steps, such as:

The read-only memory (ROM) bootstrap loader reads the Master Boot Record and passes control over to it.
The boot record loads the disk operating system into memory, and it takes control of the machine.
The computer transfers data stored on a magnetic disk to its main memory, the random access memory.
It also transfers data to external devices attached to the computer, such as a computer screen or printer.
The computer provides various applications programming interfaces for programs like character input/output, memory management, program loading, termination, and handling input from the user through a keyboard.
The OS also provides file management that organizes, reads, and writes files on storage. The files are organized in a hierarchical structure of directories, subdirectories, and files.

A disk operating system doesn’t have a graphical user interface (GUI). Its interface is character-based, so users must type commands in the command line to indicate what actions they want.

Features of DOS

Here are some of the distinguishing features of a disk operating system, such as:

MS-DOS does not offer GUI (Graphical User Interface) and doesn’t accept mouse inputs. It is a character-based interface system where all commands are entered in the text at the command-line prompt.
A disk operating system manages files, folders and allows program loading and execution. It can control hardware devices such as disk, memory and allocate resources.
MS-DOS offers a file system to organize, read and write files to the disk storage.
It is a single-user operating system and performs various tasks to ensure the proper operation of systems.
It uses a 16-bit file allocation table (FAT16), and a 16-bit interface is used to define the location of the memory of each file uniquely. These identifiers are stored in a tabular format with the name File Allocation table.
MS-DOS does not support a multiuser operating system, and it is less secure and does not have a concept of user roles. It is very lightweight due to its basic interface and limited features.

Limitations of MS-DOS

Here are the following limitations of the disk operating system, such as:

Built-in security:DOS does not have built-in security, such as file ownership and permissions.
No multiuser or multitasking:It also does not support multiuser or multitasking. It can only run one program at a time, but it provides direct access to the basic I/O system and underlying hardware.
Challenging interface: A user must type in commands and remember commands to run programs and other OS tasks. For example, typing the command cd \directory_name changes the current working directory to the named directory, and typing the command dir lists the files in the current directory. This approach makes it difficult for beginners to use.

Types of MS-DOS Commands

An instruction given to a computer to perform a specific task is known as a command. The MS-DOS has many commands to perform each task, and these commands are stored in the DOS directory of the disk. The MS-DOS commands are of two types, internal command, and external command.

Internal Command: Internal commands are built-in commands of MS-DOS, stored in the command interpreter file (COMMAND.COM). These commands reside in memory if the system is at prompt (C:\>) level. Some of the internal commands are DATE, TIME, DIR, VER, etc.
External Command: External commands are separate program (.com) files that reside in the DOS directory.

Let’s now discuss the differences between internal and external commands.

INTERNAL COMMAND	EXTERNAL COMMAND
Internal commands are loaded and executed by the operating system	User first requests to load external commands
Internal commands are faster than external commands	External commands are slower than internal commands
Internal commands are part of the shell	External commands require a path
Internal commands are stored in RAM	External commands are stored in a hard drive
These commands are built-in into the command prompt	These commands are not built-in into the command prompt
Examples of internal commands are: type, start, move, path, type, date, del, dir, cls, vol, ver, title, md, rd, prompt, copy con	Examples of external commands are: edit, label, print, help, move, comp, sort, format, backup, restore, tree, find

MS-DOS is not case-sensitive so that commands can type in either uppercase or lowercase. However, other disk operating systems have case-sensitive CLIs. DOS commands include the following.

Commands	Description
Dir	List all files of specific directories or subdirectories.
CD or CHDIR	Navigate or move to a specific directory.
RD or RMDIR	Remove directory.
TREE	Display all directory paths.
PATH	Set sequential search path for executable files.
SUBST	Substitutes a string alias for the pathname.
FORMAT	Formats a disk for DOS files.
COPY	Copies one or more files to another location.
XCOPY	Copy files and directories and their subdirectories.
Del	Delete files.
Ren or rename	Rename the name of a file or directory.
ATTRIB	Set or show file attributes.
BACKUP	Backup files and directories.
PROMPT	Customize DOS prompt.
Deltree	Deletes all files and subdirectories from a computer.
Help	Lists the available commands or more information about a specific command.
mkdir or md	Creates a new subdirectory.
Move	Moves files or directories from one directory to another or from one drive to another.
Type	Displays the contents of a file on the screen.
*	A wildcard character that represents one or more characters a group of files has in common.
?	A wildcard character that represents a single character a group of files has in common.

Example Of Ms-dos Internal Command Are:

– It is a command that allows you to clear the complete contents of the screen and leave only a prompt.
BREAK – Break can be used to enable or disable the braking capability of the computer.
REN – It is used to rename files and directories from the original name to a new name.
CHDIR – Chdir (change directory) is a command used to switch directories in MS-DOS.
EXIT – The exit command is used to withdrawal from the currently running application and the MS-DOS session.
RMDIR – Removes an empty directory in MS-DOS.
DEL- Del is a command used to delete files from the computer.
COPY – Allows you to copy one or more files to an alternate location.
VOL – Displays the volume of information about the designated drive.
TYPE- Display the contents of a text file.
DATE – The date command can be used to look at the current date of the computer as well as change the date to an alternate date.
TIME – Allows the user to view and edit the computer’s time.
DIR – The dir command displays information about files and directories, and how many spaces available.
SET – Allows you to change one variable or string to another.
MKDIR/MD – Allows you to create directories in MS-DOS.
PATH – Path is used to specify the location where MS-DOS looks when using a command.
DISKCOMP- Comparing two diskettes.
DISKCOPY- Copying a diskette.
RD- Remove a directory

Examples of External Commands are:-

DELTREE- Short for delete tree, deltree is a command used to delete files and directories permanently from the computer.
TREE- Allows the user to view a listing of files and folders in an easy to read the listing.
PRINT – The print command allows users to print a text file to a line printer, in the background.
FIND – Allows you to search for text within a file.
XCOPY – Xcopy is a powerful version of the copy command with additional features; has the capability of moving files, directories, and even whole drives from one location to another.
DISK COMP- Compares the contents of a floppy disk in the source drive to the contents of a floppy disk in the target drive.
FORMAT – Format is used to erase information off of a computer diskette or fixed drive.
ATTRIB – Attrib allows a user to change the attributes of a file or files.
SORT- Sorts the input and displays the output to the screen.
CHKDSK- Chkdsk is a utility that checks the computer’s hard drive status for any cross-linked or any additional errors with the hard drive.
FORMAT – Format a diskette.
PRINT – Printing a file.
MOVE- Allows you to move files or directories from one folder to another, or from one drive to another.

The modern computer took its shape with the arrival of your time. It had been around 16th century when the evolution of the computer started. The initial computer faced many changes, obviously for the betterment. It continuously improved itself in terms of speed, accuracy, size, and price to urge the form of the fashionable day computer. This long period is often conveniently divided into the subsequent phases called computer generations:

First Generation Computers (1940-1956)
Second Generation Computers (1956-1963)
Third Generation Computers (1964-1971)
Fourth Generation Computers (1971-Present)
Fifth Generation Computers (Present and Beyond)

Before there are graphing calculators, spreadsheets, and computer algebra systems, mathematicians and inventors searched for solutions to ease the burden of calculation.

Below are the 8 mechanical calculators before modern computers were invented.

1. Abacus (ca. 2700 BC)

2. Pascal’s Calculator (1652)

3. Stepped Reckoner (1694)

4. Arithmometer (1820)

5. Comptometer (1887) and Comptograph (1889)

6. The Difference Engine (1822)

7. Analytical Engine (1834)

8. The Millionaire (1893)

First Generation Computers: Vacuum Tubes (1940-1956)

The technology behind the primary generation computers was a fragile glass device, which was called vacuum tubes. These computers were very heavy and really large in size. These weren’t very reliable and programming on them was a really tedious task as they used low-level programming language and used no OS. First-generation computers were used for calculation, storage, and control purpose. They were too bulky and large that they needed a full room and consume rot of electricity.

Main first generation computers are:

ENIAC: Electronic Numerical Integrator and Computer, built by J. Presper Eckert and John V. Mauchly was a general-purpose computer. It had been very heavy, large, and contained 18,000 vacuum tubes.
EDVAC: Electronic Discrete Variable Automatic Computer was designed by von Neumann. It could store data also as instruction and thus the speed was enhanced.
UNIVAC: Universal Automatic Computer was developed in 1952 by Eckert and Mauchly.

Main characteristics of first generation computers are:

Main electronic component	Vacuum tube.
Programming language	Machine language.
Main memory	Magnetic tapes and magnetic drums.
Input/output devices	Paper tape and punched cards.
Speed and size	Very slow and very large in size (often taking up entire room).
Examples of the first generation	IBM 650, IBM 701, ENIAC, UNIVAC1, etc.

Main electronic component	Transistor.
Programming language	Machine language and assembly language.
Memory	Magnetic core and magnetic tape/disk.
Input/output devices	Magnetic tape and punched cards.
Power and size	Smaller in size, low power consumption, and generated less heat (in comparison with the first generation computers).
Examples of second generation	PDP-8, IBM1400 series, IBM 7090 and 7094, UNIVAC 1107, CDC 3600 etc.

Main electronic component	Integrated circuits (ICs)
Programming language	High-level language
Memory	Large magnetic core, magnetic tape/disk
Input / output devices	Magnetic tape, monitor, keyboard, printer, etc.
Examples of third generation	IBM 360, IBM 370, PDP-11, NCR 395, B6500, UNIVAC 1108, etc.

Main electronic component	Very large-scale integration (VLSI) and the microprocessor (VLSI has thousands of transistors on a single microchip).
Memory	semiconductor memory (such as RAM, ROM, etc.)
Input/output devices	pointing devices, optical scanning, keyboard, monitor, printer, etc.
Examples of fourth generation	IBM PC, STAR 1000, APPLE II, Apple Macintosh, Alter 8800, etc.

Main electronic component	Based on artificial intelligence, uses the Ultra Large-Scale Integration (ULSI) technology and parallel processing method (ULSI has millions of transistors on a single microchip and Parallel processing method use two or more microprocessors to run tasks simultaneously).
Language	Understand natural language (human language).
Size	Portable and small in size.
Input / output device	Trackpad (or touchpad), touchscreen, pen, speech input (recognize voice/speech), light scanner, printer, keyboard, monitor, mouse, etc.
Example of fifth generation	Desktops, laptops, tablets, smartphones, etc.

RAM	ROM
Definition of RAM is Random Access Memory	Definition of ROM is Read-only Memory
Random Access Memory (RAM) is expensive when compared to ROM	ROM is cheaper when compared to RAM.
The speed of Random Access Memory (RAM) is higher when compared to ROM	The speed of Read-only Memory (ROM) is slower when compared to RAM.
Random Access Memory (RAM) has a higher capacity when compared to ROM	ROM has a lower capacity compared to RAM
Data in RAM can be modified, erased, or read.	Data in ROM can only be read, it cannot be modified or erased.
The data stored in RAM is used by the Central Processing Unit (CPU) to process current instructions	The data stored in ROM is used to bootstrap the computer.
Data stored on RAM can be accessed by the Central Processing Unit.	If the Central Processing Unit (CPU) needs to access the data on ROM, first the data must be transferred to RAM, and then the Central Processing Unit (CPU) will be able to access the data.
Data of RAM is very volatile, it will exist as long as there is no interruption in power.	Data present in Read-Only Memory (ROM) is not volatile, it is permanent. Data will remain unchanged even when there is a disruption in the power supply.