01 Computer System
1.1 Introduction to Computer System
A computer system is an electronic system designed to accept data, process it according to a set of instructions, store it, and produce meaningful information as output. The NCERT textbook introduces the computer system not merely as a machine, but as a combination of hardware, software, data, users, and procedures working together.
In simple terms, a computer system performs the following basic operations:
- Input – Accepting data and instructions
- Processing – Performing operations on the data
- Output – Producing results
- Storage – Saving data and results for future use
These four operations form the IPO cycle (Input–Process–Output), which is the foundation of all computing systems.
Definition of a Computer
According to the NCERT description, a computer is an electronic device that:
- Works at very high speed
- Performs operations accurately
- Can store large amounts of data
- Can be programmed to perform a wide variety of tasks
However, a computer does not possess intelligence of its own. It works strictly according to the instructions provided by the user, which are known as programs.
Characteristics of a Computer System
The NCERT textbook highlights several important characteristics of a computer system:
1. Speed
A computer can perform millions or even billions of operations per second. Tasks that take humans hours can be completed by a computer in seconds.
2. Accuracy
A computer produces highly accurate results, provided the input data and instructions are correct. Errors occur mainly due to incorrect input or faulty programs, not because of the computer itself.
3. Storage Capability
A computer system can store vast amounts of data and information. This data can be retrieved quickly whenever required.
4. Automation
Once a program is loaded and started, the computer performs tasks automatically without human intervention.
5. Versatility
A computer can be used for multiple purposes, such as calculations, data analysis, communication, entertainment, and control of machines.
Limitations of a Computer
NCERT also clearly states that computers have limitations:
- A computer cannot think or make decisions on its own
- It has no emotions or intelligence
- It works strictly as per the instructions given
Understanding these limitations is important to avoid misconceptions about computers.
Components of a Computer System
A computer system is made up of the following major components:
- Hardware
- Software
- Data
- Users
- Procedures
At this level, NCERT mainly focuses on hardware and software, while data and users are discussed conceptually.
Block Diagram of a Computer System (Conceptual Explanation)
A typical computer system consists of:
- Input Unit – Accepts data and instructions
- Central Processing Unit (CPU) – Processes data
- Memory Unit – Stores data and instructions
- Output Unit – Produces results
The CPU is further divided into:
- Arithmetic Logic Unit (ALU)
- Control Unit (CU)
Together, these components coordinate all activities of the computer system.
Role of Computer Systems in Everyday Life
NCERT emphasizes the widespread use of computer systems in daily life, including:
- Education (online learning, digital exams)
- Business (billing, accounting, inventory)
- Healthcare (medical records, diagnostics)
- Banking (ATMs, online transactions)
- Communication (emails, video conferencing)
This makes computer literacy essential in the modern world.
Key NCERT-Oriented Points to Remember
- A computer system performs input, processing, output, and storage
- It works on the principle of IPO cycle
- Speed, accuracy, and storage are major strengths
- Computers do not have intelligence or emotions
- Hardware and software together form a computer system
1.2 Evolution of Computer
Computers did not appear suddenly in their present form. The modern computer system is the result of continuous development over several decades. The NCERT textbook explains the evolution of computers as a gradual process in which improvements were made in speed, size, storage capacity, cost, and reliability.
The evolution of computers is commonly studied by dividing it into generations, where each generation is marked by a major technological advancement in computer hardware.
Early Computing Devices (Before Electronic Computers)
Before electronic computers were developed, humans used manual and mechanical devices to perform calculations.
Some early devices include:
- Abacus – Used for basic arithmetic calculations
- Napier’s Bones – Used for multiplication and division
- Pascaline – Mechanical calculator developed by Blaise Pascal
- Analytical Engine – Designed by Charles Babbage (conceptual foundation of modern computers)
Charles Babbage is often called the Father of the Computer because his Analytical Engine introduced ideas such as:
- Input
- Processing
- Output
- Memory
These concepts are still used in modern computer systems.
Generations of Computers
The NCERT textbook classifies the evolution of computers into five generations, based on the primary technology used in their construction.
First Generation Computers (1940–1956)
Technology Used
- Vacuum Tubes
Vacuum tubes were used for:
- Data processing
- Control
- Memory
Characteristics of First Generation Computers
- Very large in size
- Consumed huge amounts of electricity
- Generated excessive heat
- Very expensive
- Limited storage capacity
- Low reliability
Programming was done using machine language, which was difficult to write and understand.
Examples
- ENIAC (Electronic Numerical Integrator and Computer)
- EDVAC
- UNIVAC
📌 NCERT Exam Point First-generation computers used vacuum tubes and were extremely large and power-hungry.
Second Generation Computers (1956–1963)
Technology Used
- Transistors
Transistors replaced vacuum tubes and brought major improvements.
Characteristics of Second Generation Computers
- Smaller in size compared to first generation
- Consumed less power
- Produced less heat
- More reliable
- Faster processing
- Cheaper than first-generation computers
Programming languages such as assembly language and early high-level languages started to be used.
Examples
- IBM 1401
- IBM 7094
📌 NCERT Observation The invention of transistors made computers more practical and reliable.
Third Generation Computers (1964–1971)
Technology Used
- Integrated Circuits (ICs)
An integrated circuit contains multiple transistors on a single silicon chip.
Characteristics of Third Generation Computers
- Much smaller in size
- Higher speed and efficiency
- Reduced power consumption
- Less heat generation
- Improved reliability
- Better storage capacity
Operating systems were introduced, allowing multiprogramming and better resource management.
Examples
- IBM System/360
- PDP-8
📌 NCERT Exam Point Integrated circuits marked the beginning of third-generation computers.
Fourth Generation Computers (1971–Present)
Technology Used
- Microprocessors
A microprocessor contains the entire CPU on a single chip.
Characteristics of Fourth Generation Computers
- Very small size (personal computers)
- Very high processing speed
- Low cost
- Large storage capacity
- High reliability
- Easy to use
This generation saw the development of personal computers (PCs), laptops, and mobile devices.
Examples
- IBM PC
- Apple Macintosh
📌 NCERT Observation Microprocessors revolutionised computing by making computers accessible to individuals.
Fifth Generation Computers (Present and Future)
Technology Used
- Artificial Intelligence (AI)
- Machine Learning
- Natural Language Processing
Fifth-generation computers aim to simulate human intelligence.
Characteristics of Fifth Generation Computers
- Use of AI techniques
- Ability to learn and make decisions
- Very high processing capability
- Used in robotics, expert systems, and advanced research
Although still under development, many AI-based systems already exist today.
Examples
- AI-based systems
- Robotics
- Intelligent assistants
Summary Table: Generations of Computers
| Generation | Technology Used | Key Feature |
|---|---|---|
| First | Vacuum Tubes | Very large, high power |
| Second | Transistors | Smaller, more reliable |
| Third | Integrated Circuits | Faster, compact |
| Fourth | Microprocessors | Personal computers |
| Fifth | AI Technologies | Intelligent systems |
Key Points to Remember (NCERT-Oriented)
- Computers evolved over several generations
- Each generation introduced major hardware improvements
- Size decreased while speed and efficiency increased
- Cost reduced significantly over generations
- Present computers are based on microprocessors
1.3 Computer Memory
A computer system works with large amounts of data and instructions. For efficient functioning, it requires a place where data and instructions can be stored, retrieved, and processed. This storage space is known as computer memory.
According to NCERT, computer memory refers to the physical devices used to store:
- Data
- Instructions (programs)
- Results of processing
Without memory, a computer cannot perform even the simplest task.
Need for Computer Memory
Computer memory is required to:
- Store input data before processing
- Hold instructions during execution
- Store intermediate results
- Store final output
- Retain data for future use
Thus, memory plays a central role in the functioning of a computer system.
Units of Memory
Data in a computer is stored in binary form (0s and 1s). The smallest unit of memory is a bit.
Common Memory Units
| Unit | Description |
|---|---|
| Bit | Binary digit (0 or 1) |
| Nibble | 4 bits |
| Byte | 8 bits |
| Kilobyte (KB) | 1024 bytes |
| Megabyte (MB) | 1024 KB |
| Gigabyte (GB) | 1024 MB |
| Terabyte (TB) | 1024 GB |
📌 NCERT Exam Point Memory units increase in powers of 1024, not 1000.
Classification of Computer Memory
The NCERT textbook classifies computer memory into two main categories:
- Primary Memory (Main Memory)
- Secondary Memory (Auxiliary Memory)
1.3.1 Primary Memory
Primary memory is the memory that is directly accessible by the CPU. It stores:
- Programs currently in execution
- Data being processed
- Intermediate and final results
Primary memory is also called main memory.
Characteristics of Primary Memory
- Fast access speed
- Limited storage capacity
- More expensive
- Volatile or non-volatile (depending on type)
- Essential for program execution
Types of Primary Memory
Primary memory is mainly of two types:
- RAM (Random Access Memory)
- ROM (Read Only Memory)
Random Access Memory (RAM)
RAM is a volatile memory that temporarily stores:
- Programs
- Data currently in use
The contents of RAM are lost when power is switched off.
Characteristics of RAM
- Volatile in nature
- Fast read/write access
- Stores active programs and data
- Directly accessible by CPU
Types of RAM (NCERT-Oriented)
1. Static RAM (SRAM)
- Faster
- More expensive
- Used in cache memory
2. Dynamic RAM (DRAM)
- Slower than SRAM
- Cheaper
- Used as main memory
📌 NCERT Exam Point RAM is volatile memory and loses its contents when power is off.
Read Only Memory (ROM)
ROM is a non-volatile memory that stores permanent instructions required to start the computer.
These instructions are known as firmware.
Characteristics of ROM
- Non-volatile in nature
- Contents are not lost when power is off
- Stores booting instructions
- Cannot be modified easily
Types of ROM
| Type | Description |
|---|---|
| PROM | Programmable ROM |
| EPROM | Erasable Programmable ROM |
| EEPROM | Electrically Erasable PROM |
📌 NCERT Observation ROM stores instructions required to boot the computer system.
Difference Between RAM and ROM
| RAM | ROM |
|---|---|
| Volatile | Non-volatile |
| Read and write | Mostly read-only |
| Temporary storage | Permanent storage |
| Stores running programs | Stores boot instructions |
1.3.2 Secondary Memory
Secondary memory is used to store data and programs permanently for future use. It is not directly accessed by the CPU.
Characteristics of Secondary Memory
- Non-volatile
- Large storage capacity
- Slower than primary memory
- Cheaper than primary memory
- Used for long-term storage
Types of Secondary Memory
1. Magnetic Storage
- Hard Disk
- Magnetic Tape
2. Optical Storage
- CD
- DVD
- Blu-ray Disc
3. Solid State Storage
- Pen Drive
- SSD
- Memory Card
📌 NCERT Exam Point Secondary memory retains data even after power is switched off.
Difference Between Primary and Secondary Memory
| Primary Memory | Secondary Memory |
|---|---|
| Direct CPU access | Indirect access |
| Fast | Slow |
| Limited capacity | Large capacity |
| Expensive | Cheaper |
| Temporary (RAM) | Permanent |
Memory Hierarchy (Conceptual)
NCERT introduces the idea that memory is organised in a hierarchy based on:
- Speed
- Cost
- Capacity
From top to bottom:
- Registers
- Cache Memory
- Primary Memory
- Secondary Memory
Key Points to Remember (NCERT-Oriented)
- Memory stores data and instructions
- Bit is the smallest unit of memory
- Primary memory is directly accessed by CPU
- RAM is volatile; ROM is non-volatile
- Secondary memory provides permanent storage
- Memory hierarchy balances speed and cost
1.4 Software
A computer system cannot perform any task on its own without instructions. These instructions are provided in the form of software. While hardware represents the physical components of a computer, software represents the intangible part that tells the hardware what to do and how to do it.
According to NCERT, software is a collection of programs, procedures, and related documentation that enables a computer system to perform specific tasks.
Need for Software
Hardware alone is useless without software. Software is required to:
- Control the working of hardware
- Convert user instructions into machine-understandable form
- Perform specific tasks such as calculations, document creation, and data management
- Act as an interface between the user and the hardware
Thus, software plays a crucial role in making a computer system functional.
Classification of Software
The NCERT textbook classifies software into two main categories:
- System Software
- Application Software
This classification is very important from an examination point of view.
1.4.1 System Software
System software is a type of software that manages and controls the overall operation of the computer system. It acts as a bridge between the hardware and the user/application software.
System software is usually loaded into the computer memory when the system is started.
Functions of System Software
System software performs the following functions:
- Controls hardware resources
- Manages memory and processor
- Provides a platform for application software
- Controls input and output devices
- Ensures smooth operation of the computer system
Types of System Software
NCERT broadly includes the following under system software:
- Operating System
- Language Processors
- Utility Software
Operating System (OS)
An operating system is the most important system software. It controls all activities of the computer and acts as an interface between the user and the hardware.
Functions of an Operating System
- Process management
- Memory management
- File management
- Device management
- User interface
Examples of operating systems include:
- Windows
- Linux
- macOS
📌 NCERT Exam Point The operating system is the first software loaded into memory when the computer starts.
Language Processors
A computer understands only machine language. Language processors translate programs written in high-level or assembly languages into machine language.
Types of language processors include:
- Assembler
- Compiler
- Interpreter
Each performs translation in a different way.
Utility Software
Utility software helps in the maintenance and proper functioning of the computer system.
Examples include:
- Antivirus software
- Disk cleanup tools
- Backup utilities
- File compression tools
Utility software improves system performance and security.
1.4.2 Application Software
Application software is designed to perform specific tasks for the user. Unlike system software, application software is user-oriented.
Application software runs on top of the operating system.
Functions of Application Software
Application software helps users to:
- Create documents
- Perform calculations
- Manage data
- Design graphics
- Communicate and browse the internet
Types of Application Software
NCERT classifies application software into two categories:
- General Purpose Application Software
- Specific Purpose (Customised) Application Software
General Purpose Application Software
These are commonly used software packages designed for general use.
Examples include:
- Word processors
- Spreadsheets
- Presentation software
- Database management systems
Such software can be used by many users for different purposes.
Specific Purpose (Customised) Application Software
These software are developed for a specific organisation or task.
Examples include:
- School management system
- Railway reservation system
- Hospital management system
- Banking software
These are tailored to meet specific requirements.
Difference Between System Software and Application Software
| System Software | Application Software |
|---|---|
| Controls system operations | Performs user tasks |
| Runs in background | Runs when user requests |
| Essential for system | Optional but useful |
| Example: OS | Example: Word processor |
Firmware (Conceptual)
NCERT also introduces the concept of firmware indirectly.
- Firmware is software stored in ROM
- It provides instructions required to start the computer
- BIOS is an example of firmware
Firmware lies between hardware and software.
Key Points to Remember (NCERT-Oriented)
- Software is a set of programs
- Hardware cannot work without software
- Software is classified into system and application software
- Operating system is the core system software
- Application software performs user-specific tasks
- Utility software helps maintain the system