UNIT I:

Basic Structure Of Computers: Computer Types, Functional unit, Basic Operational concepts,
Bus structures, Software, Performance, multiprocessors and multi computers.
Logic gates: Digital Logic gates, Two-level realizations using gates -- AND-OR, OR-AND,
NAND-NAND and NOR-NOR

Computer Types
A computer is an electronic device that has storage, computations, input (data), output (data) and
networking capabilities. With the growing AI, computers also have learning capabilities from the
data provided. The input and output data can be in different forms like text, images, audio and
video. A computer processes the input according to the set of instructions provided to it by the user
and gives the desired output. Computers are of various types, and they can be categorized in two
ways on the basis of size and on the basis of data handling capabilities.

Types of Computer
There are two bases on which we can define the types of computers. We will discuss the type of
computers on the basis of size and data handling capabilities. We will discuss each type of
computer in detail. Let’s see first what are the types of computers.

➢ Super Computer
➢ Mainframe computer
➢ Mini Computer
➢ Workstation Computer
➢ Personal Computer (PC)
➢ Server Computer
➢ Analog Computer
➢ Digital Computer
➢ Hybrid Computer
➢ Tablets and Smartphone

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 that 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 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.

Mainframe computer
Mainframe computers are designed in such a way that they 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.

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

Characteristics of Workstation Computer

• It is expensive or high in cost.
• They are exclusively made for complex work purposes.
• It provides large storage capacity, 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.

Personal Computer (PC)

Personal Computers is also known as a microcomputer. It is basically a general-purpose computer
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 the office for office work, etc. For example,
Laptops and desktop computers.

Characteristics of Personal Computer (PC)

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

Server Computer
Server Computers are computers that are combined data and programs. Electronic data and
applications are stored and shared in the server computer. The working of a server computer is that
it does not solve a bigger problem like a supercomputer but it solves many smaller similar ones.
Examples of server computer are like Wikipedia, as when users put a request for any page, it finds
what the user is looking for and sends it to the user.

Characteristics:
• Handles data and applications for multiple clients or users.
• Centralized management of resources (e.g., databases, websites).
• Designed to run 24/7 without interruption.
• More powerful than a typical PC and optimized for networking and data management.
Examples:

✓ Web servers (e.g., Apache HTTP Server)

✓ Database servers (e.g., SQL Server, Oracle)

Based on Data-Handling Capabilities

Analog Computer
Analog Computers are particularly designed to process analog data. Continuous data that changes
continuously and cannot have discrete values are called analog data. So, an analog 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.

Characteristics:

• Handles continuous data.

• Real-time data processing without needing to convert it into digital form.
• Used in applications where approximate values are sufficient.

Examples:

✓ Speedometer (for measuring vehicle speed)

✓ Thermometers (mercury thermometer)

Digital Computer
Digital computers are designed in such a way that they can easily perform calculations and logical
operations at high speed. It takes raw data as 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.

Characteristics:

• Processes data in the form of binary digits (0s and 1s).

• Handles precise, accurate data and complex operations, including calculations, logical
operations, and storage.
• Fast data processing and capable of running various applications from entertainment to
business management.

Examples:

✓ Laptops
✓ Desktops
✓ Smartphones
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 analog computers and have memory and accuracy like digital computers. 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 are 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.

Characteristics:

• Can handle both analog and digital data.

• Real-time processing with high accuracy.
• Often used in applications where both types of data are needed.

Examples:

✓ Petrol pump processors that convert fuel flow measurements into digital format (quantity
and price).
✓ Medical equipment like ECG (Electrocardiogram) machines

Tablet and Smartphones

Tablets and Smartphones are the types of computers that are pocket friendly and easy to carry is
these are handy. This is one of the best use of modern technology. These devices have better
hardware capabilities, extensive operating systems, and better multimedia functionality.
smartphones and tablets contain a number of sensors and are also able to provide wireless
communication protocols.

Characteristics:

• Portable and compact in size.

• Touch-screen interface and multiple sensors.
• Wireless communication protocols (Wi-Fi, Bluetooth, etc.).
• Capable of running a wide variety of apps for productivity, entertainment, and
communication.

Examples:
✓ Smartphones – iPhone, Samsung Galaxy
✓ Tablets – iPad, Samsung Galaxy Tab
Functional unit

The functional components of a digital computer include the Input Unit, which takes in data; the
CPU, which processes data with its Control Unit (CU), Arithmetic Logic Unit (ALU), and
Registers; the Memory Unit, which stores data temporarily (RAM) or permanently (HDD/SSD);
the Output Unit, which displays results; and the Bus System, which connects and transfers data
between components. These parts work together to execute tasks and provide results.

The functional components of a computer are the key parts that work together to process and
manage data. These include the Input Unit for receiving data, the CPU for processing it, the
Memory Unit for storing information, the Output Unit for displaying results, and the Bus System
that connects all parts. These components help the computer perform tasks efficiently.

Input Unit
Purpose: Captures data and instructions from users or external sources.
Function: Converts user input into binary signals that the computer can process.

Common Devices (2025):

➢ Keyboard, Mouse, Touchscreens
➢ Scanners, Sensors, Stylus pens
➢ Voice Assistants (e.g., Siri, Alexa)
➢ Biometric devices (face/fingerprint recognition)
➢ Iot-based inputs from smart devices

Central Processing Unit (CPU) – The Brain of the Computer

The CPU executes instructions and controls all internal operations. In 2025, CPUs will often have
multiple cores and threads to handle parallel processing efficiently.

Components of CPU:
a. Arithmetic Logic Unit (ALU)
• Performs arithmetic operations (add, subtract, multiply, divide).
• Handles logical operations (comparison, decision-making).
• Supports AI/ML tasks using built-in vector/matrix operations (in modern CPUs).
b. Control Unit (CU)
 • Directs the operations of all computer parts.
• Decodes instructions and coordinates data flow.
• Sends control signals to memory and I/O devices.
c. Registers
• High-speed memory locations within the CPU.
• Temporarily store instructions, addresses, and intermediate data.
• Examples: Accumulator, Instruction Register, Program Counter, Address Register.
• Modern CPUs include 64-bit or even 128-bit registers for faster processing.

3. Memory / Storage Unit

The memory unit holds data and instructions before, during, and after processing.

a. Primary Memory (Main Memory):

➢ RAM (Random Access Memory): Temporarily stores data during execution.
o Types in 2025: DDR5, LPDDR5X, and emerging MRAM.
➢ ROM (Read-Only Memory): Stores boot-up instructions and firmware.
➢ Cache Memory: Ultra-fast memory between CPU and RAM (L1, L2, L3 levels).

b. Secondary Storage:
➢ Used for long-term data storage.
➢ Examples: SSDs (NVMe drives), HDDs, flash drives, and cloud storage.
➢ Modern Trend: Use of Cloud Integration and hybrid storage models.

4. Output Unit
• Purpose: Converts processed data (binary) into a form users can understand.
• Examples:
o Visual: Monitors (LED, OLED, 4K/8K displays)
o Print: Printers (Inkjet, Laser, 3D Printers)
o Audio: Speakers, Headphones
o Haptic: Vibration feedback devices
• Emerging Tech: AR/VR headsets, voice-based output, Braille displays for accessibility

Basics of Computer and its Operations

A computer is an electronic device that can receive, store, process, and output data. In simple
terms, it’s a machine that helps us perform all sorts of tasks, from basic calculations to complex
activities like playing games, watching videos, or even running artificial intelligence programs.

Computers have two main parts: Hardware and Software

Hardware refers to the physical parts of the computer, like the central processing unit (CPU),
memory, storage devices, input/output devices (like keyboards and screens), and other peripherals
(extra devices connected to the computer).

Software refers to the programs and applications that tell the computer what to do. This includes
things like the operating system (such as Windows or macOS) and the apps you use for
schoolwork, games, and more.
Data and Information
Data and information are related concepts, but they have different meanings. Data refers to raw
facts and figures that are unorganized and have no meaning on their own. Information, on the other
hand, is data that has been processed, organized, and given context to make it meaningful and
useful.

Data can be numbers, words, images, or sounds. For example, a list of sales figures is just data.
On its own, it doesn’t tell us much. To make it useful, we need to process and analyze it.

Information is what we get after processing data. It’s organized in a way that helps us understand
something or answer a question. For example, turning the sales numbers into a graph or chart
shows trends over time and gives us useful information about the company’s performance.

Classification of Computers
Computers can be classified based on various factors, including their size, functionality, purpose,
and processing capabilities. Here's a breakdown of the classification of computers:

➢ Based on Size and Power

➢ Based on Purpose
➢ Based on Data Handling
➢ Based on Architecture
➢ Based on Functionality
➢ Based on Usage

Peripheral Devices
Peripheral devices are external hardware components that are connected to a computer to expand
its functionality. These devices can be categorized into input devices, output devices, and storage
devices.

Here’s an overview of the main peripheral devices:

1. Input Devices
Input devices allow users to provide data and commands to the computer.

➢ Keyboard: Used to type text and enter commands into the computer.
➢ Mouse: A pointing device used to move the cursor and interact with objects on the screen.
➢ Scanner: Converts physical documents and images into digital form.
➢ Microphone: Captures audio and converts it into digital data for the computer to process.
➢ Digital Camera/Webcam: Captures video or images, often for video conferencing or
photography.
➢ Touchpad: A touch-sensitive surface used on laptops to move the cursor and interact with
the computer.

2. Output Devices
Output devices display or produce the results of a computer's processing.

➢ Monitor: A screen that displays visual output from the computer.

➢ Printer: A device that produces a physical copy (paper printout) of documents, images, or
graphics.
➢ Speakers: Convert digital audio data into sound so users can hear music, videos, or other
audio output.
 ➢ Headphones: Provide personal audio output by converting digital sound signals into
audible sound.
➢ Projector: Projects computer content (images, videos) onto a larger screen or surface.

3. Storage Devices
Storage devices are used to store data for the computer.

➢ Hard Disk Drive (HDD): A traditional storage device that stores large amounts of data on
rotating disks.
➢ Solid-State Drive (SSD): A faster and more reliable storage device that uses flash memory.
➢ USB Flash Drive: A portable storage device that connects via a USB port to transfer and
store data.
➢ Optical Disc Drives: Devices like CD/DVD/Blu-ray drives that read and write data on
optical discs.
➢ Memory Card: Small storage devices, like SD cards or microSD cards, used in cameras,
smartphones, and other portable devices.

4. Communication Devices
These devices help a computer connect with other devices or networks.

➢ Modem: A device that allows a computer to connect to the internet over a phone or cable
line.
➢ Router: A networking device that connects multiple devices to the internet or a local
network.
➢ Bluetooth Adapter: A device that allows a computer to communicate wirelessly with
Bluetooth-enabled devices.

RAM Hard Disk

RAM is an electronic device Hard-disk is an electromechanical device

Electro-mechanical device has speed slower than

Electronic device are faster in speed
Electronic device.

CPU is an electronic device, so it's speed can

Hard disk is an electro-mechanical device. Therefore, it's
match with RAM. Therefore, CPU and RAM have
speed cannot be match by CPU and hence there is no
connections and that connections is known as
connection between hard-disk and CPU.
buses

RAM is much faster than a hard-disk. RAM is a Hard-disk is a type of non-volatile storage that is much
type of volatile memory that can be accessed slower than RAM. It is used for long-term storage of data
quickly by the CPU. This allows for fast data that needs to be preserved even when the computer is
processing and multitasking. turned off.

Hard-disk is non-volatile, meaning that its contents are

RAM is volatile, meaning that its contents are lost preserved even when the computer is turned off. This
when the computer is turned off. makes hard-disk an ideal choice for long-term storage of
data.
Types of Software
Here are the main types of software

1. System Software
✓ Operating Systems (OS): Manages computer hardware and software resources (e.g.,
Windows, macOS, Linux).
✓ Utility Software: Helps maintain and optimize the system (e.g., antivirus software, disk
management tools).
✓ Device Drivers: Enable hardware components to work with the operating system (e.g.,
printer drivers, graphics card drivers).

2. Application Software
✓ Productivity Software: Used for creating documents, presentations, and managing data
(e.g., Microsoft Office, Google Docs).
✓ Multimedia Software: Used for creating, editing, and playing audio, video, and images
(e.g., Adobe Photoshop, VLC Media Player).
✓ Web Browsers: Software used to access and navigate the internet (e.g., Google Chrome,
Mozilla Firefox).
✓ Games: Entertainment software designed for gaming (e.g., Fortnite, Minecraft).
✓ Educational Software: Used for learning or teaching purposes (e.g., Khan Academy,
Duolingo).

3. Development Software
✓ Programming Languages: Tools used for writing software programs (e.g., Python, Java,
C++).
✓ Integrated Development Environments (IDEs): Provide a platform for developers to write
and test code (e.g., Visual Studio, Eclipse).
✓ Database Management Software (DBMS): Manages data storage and retrieval (e.g.,
MySQL, Oracle).

4. Firmware
✓ Embedded Software: Special software stored in hardware devices to control them (e.g.,
software in washing machines, cameras, or smart thermostats).

Basic Computer Operation

1. Booting up: This is the process of starting up the computer by loading the operating system
(OS) into memory. The computer runs a series of checks to ensure all hardware is working
correctly before loading the OS.
2. Logging in: After booting up, you will need to log in to access your user account. This
requires entering your username and password.
3. Running programs: Once you have logged in, you can run programs on your computer.
Programs can include web browsers, office applications, media players, and more.
4. Accessing data: You can access data stored on your computer or other connected devices,
such as external hard drives or cloud storage services. This can include files, documents,
photos, and other media.
5. Connecting to the internet: You can connect to the internet to access websites, download
files, and communicate with others online. This typically involves using a web browser to
access websites and other online services.
6. Communicating with other devices: You can communicate with other devices connected
to your computer, such as printers, scanners, or other peripherals. This allows you to print
documents, scan images, and perform other tasks.
 7. Saving and backing up data: It's important to save and back up your data regularly to
avoid data loss. You can save data to your local hard drive, external hard drives, or cloud
storage services.
8. Shutting down: When you're finished using your computer, you should shut it down
properly. This involves closing all programs and files, saving any changes, and shutting
down the OS.
9. Troubleshooting: If you experience issues with your computer, you may need to
troubleshoot the problem. This can involve diagnosing hardware or software issues,
performing updates, or reinstalling drivers.
10. Security: It's important to keep your computer secure by using antivirus software, firewalls,
and other security measures. This helps protect your data and prevent unauthorized access
to your system.

Issues of Basic Computers and Computer Operations

some common issues that can arise with basic computers and computer operations:

1. Slow performance: Computers can become slow and unresponsive due to a variety of
factors, such as lack of storage space, outdated hardware, or malware.
2. Malware and viruses: Malware and viruses can infect computers and cause a range of
problems, including data loss, system crashes, and identity theft.
3. Hardware failures: Computer hardware components can fail over time, leading to issues
like system crashes, data loss, and display problems.
4. Software glitches: Software applications can sometimes malfunction or crash, leading to
issues like data loss or unresponsive programs.
5. Driver problems: Drivers are software components that enable hardware devices to
communicate with the operating system. If drivers become outdated or corrupted, it can
lead to issues like hardware failures or system crashes.
6. Compatibility issues: Sometimes software applications or hardware components may not
be compatible with each other, leading to issues like system crashes or display problems.
7. Internet connectivity issues: Problems with internet connectivity can lead to issues like
slow loading web pages, interrupted downloads, and difficulty accessing online services.
8. User error: Users can sometimes make mistakes or accidentally delete files or programs,
leading to issues like data loss or unresponsive programs.

Bus structures

A computer bus is a communication system used to transfer data between components within a
computer or between different computers. It plays a crucial role in minimizing the number of
connections needed by centralizing communication over shared pathways.

➢ It consists of physical connections like wires, circuits, or cables.

➢ Components like the CPU, memory, and input/output (I/O) devices are connected through
a bus.
➢ It simplifies data transfer and improves efficiency.
Types of Computer Buses
There are three main types of buses in a computer system which are discussed below:

1. Address Bus
A collection of wires used to identify particular location in main memory is called Address Bus.
Or in other words, the information used to describe the memory locations travels along the address
bus.

➢ The address bus transports memory addresses which the processor wants to access in order
to read or write data..
➢ The address bus is unidirectional.
➢ The size of address bus determines how many unique memory locations can be addressed.

Example:
✓ A system with 4-bit address bus can address 24 = 16 Bytes of memory.
✓ A system with 16-bit address bus can address 216 = 64 KB of memory
✓ A system with 20-bit address bus can address 220 = 1 MB of memory.

2. Data Bus
A collection of wires through which data is transmitted from one part of a computer to another is
called Data Bus. It can be thought of as a highway on which data travels within a computer.

➢ The main objective of data bus is transfer of the data between microprocessor to input/
output devices or memory.
➢ The data bus transfers instructions coming from or going to the processor.
➢ The data bus is bidirectional because the data can flow in either direction from CPU to
memory(or input/output device) or from memory to the CPU.
➢ The size (width) of bus determines how much data can be transmitted at one time.
Example:
✓ A 16-bit bus can transmit 16 bits of data at a time.
✓ 32-bit bus can transmit 32 bits at a time.

3. Control Bus
The connections that carry control information between the CPU and other devices within the
computer is called Control Bus. The control bus transports orders and synchronization signal
coming from the control unit and travelling to all other hardware components

➢ The main objective of control bus is all signals controller carried from processor to other
hardware device.
➢ The Control bus is bidirectional because the data can flow in either direction from CPU to
memory (or input/output device) or from memory to the CPU.
➢ it also transmits response signals from the hardware.

Example:
✓ This bus is used to indicate whether the CPU is reading from memory or writing to
memory.

Bus Type Direction Purpose Key Role

Address Bus Unidirectional Carries memory addresses Identifies where data should
go
Data Bus Bidirectional Carries actual data Moves data between
components
Control Bus Bidirectional Carries control and sync Coordinates CPU and device
signals actions