Computer Organization Notes – Class 11 IT (802) | Quick Revision

Get the best Computer Organization Notes of Class 11 IT (802) with simplified explanations, pointwise concepts, easy to understand, and exam-oriented revision material to score high in CBSE exams.

Session-1: Fundamentals of Computer

What is Computer System

• The term computer comes from the word “compute”, which means to calculate.
• A computer is an electronic device that:
  • Takes input from the user
  • Processes it according to instructions
  • Produces output
• It works based on a set of predefined instructions.

Evolution of Computers

• The growth of the computer industry started with the need for fast calculations.
• Manual computing methods were slow and error-prone.
• To overcome this, faster calculating devices were developed.
• The journey began with the Abacus, the first calculating device.
• Over time, computing devices evolved into highly advanced and extremely fast machines.

Computer and Binary Language

• A computer is an electronic device that works on electronic signals.
• These signals are represented using: 0 (OFF state) and 1 (ON state)
• This system is called Binary Language or Machine Language.

Characteristics of a Computer

• Speed: Computers process data and instructions at very high speed. A high-speed computer can perform about 3–4 MIPS (Million Instructions Per Second).
• Versatility: Computers can perform different types of tasks easily such as calculations, documentation, presentations, games, database management, and communication.
• Accuracy: Computers produce highly precise and correct output. Errors usually occur due to human input, not machine processing.
• Diligence: Computers can perform repetitive tasks continuously without losing efficiency or accuracy.
• Memory: Computers have the ability to store data temporarily or permanently, and it is one of the most important features of a computer.
• Intelligence: Earlier computers were not intelligent and only followed instructions. Modern computers using AI can make decisions and improve their performance through self-adjustment.

Components of a Computer

• A computer is made up of two main parts: hardware and software.
  • Hardware refers to the physical parts of a computer that we can touch, such as the motherboard, memory devices, monitor, keyboard, mouse, etc.
  • Software refers to the set of programs or instructions that tell the computer what to do.
• Both hardware and software work together to make a computer system function properly.
• Every task is performed by computer follows IPO cycle: Input → Process → Output.

Input

Data and instructions are given to the computer using input devices like a keyboard or mouse. A set of instructions given to the computer is called a program.

Storage/Memory

• The data and instructions are stored temporarily or permanently during processing.
• Computer Storage is mainly of two types:
  • Primary Memory
  • Secondary Memory

Primary Memory

• Primary memory is the memory that is directly accessible by the CPU.
• The data and instructions received from input devices are stored in this memory during processing.
• It is also called main memory or working memory.
• Primary Memory is of two types:
  • RAM (Random Access Memory)
  • ROM (Read Only Memory)

RAM (Random Access Memory)

• RAM is a volatile memory, which means its data is lost when the power is turned off.
• Used for storing data and instructions currently in use
• Faster access compared to secondary storage

Types of RAM:

DRAM	SRAM
Dynamic RAM	Static RAM
Used in main memory	Used in cache memory
Less expensive	Expensive
Less power consumption	More power consumption
Slower	Faster

ROM (Read Only Memory)

• ROM is a non-volatile memory, which means its data is not lost when the power is turned off.
• Mainly used during the startup (booting) process of a computer
• Stores permanent instructions

Types of ROM:

• ROM – Basic fixed memory
• PROM (Programmable Read Only Memory) – Can be programmed once
• EPROM (Erasable Programmable Read Only Memory) – Can be erased using UV light and reprogrammed
• EEPROM (Electrically Erasable Programmable Read Only Memory) – Can be erased and rewritten electrically

Secondary Storage

• Secondary storage is the memory that is external to the computer system. It is used to store data and programs permanently.
• It is not directly connected to the CPU.
• Examples of Secondary Storage: Magnetic tapes, Hard disk, CD/DVD (CD-ROM), Pen drive

Cache Memory

• Cache memory is a very high-speed memory used to increase the speed of the CPU.
• It is placed between the CPU and main memory (RAM).
• It acts as a buffer between CPU and RAM.
• It reduces the average time required to access data from main memory.
• It is faster but more expensive than primary memory.

Processing

• The input provided by the user is processed by the Central Processing Unit (CPU)
• The result of this processing is then either sent to the output devices or stored in a memory location for future use.

Control Unit (CU)

• The Control Unit manages and coordinates all activities of the computer.
• It controls input, processing, and output operations.

Arithmetic Logic Unit (ALU)

• The ALU performs all mathematical and logical operations.
• Performs arithmetic operations like addition, subtraction, etc.
• Performs logical comparisons (>, <, =, etc.)

Output Unit

• The output unit displays the final result of processing.
• It shows results on devices like monitor, printer, speakers, etc.

Block Diagram of Computer

Session-2: Components of Computer

Motherboard

• Main circuit board of computer.
• Connects all components: CPU, Memory, Hard Disk, Ports (USB, PS2), Expansion cards
• Acts as backbone of system

Input Devices

• Keyboard – text input
• Mouse – pointing device
• Webcam – image/video capture
• Scanner – converts documents to digital form (soft copy)
• Microphone – audio input

Output Devices

• Monitor/VDU – standard display screen
• Speaker – sound output
• Printer – produces printed documents/images
• Plotter – large-scale prints (maps/designs)
• Projector – displays enlarged output for audience

CPU (Central Processing Unit)

• The CPU (Central Processing Unit) is the main processor of the computer and is located on the motherboard.
• It is mainly responsible for the overall performance and speed of the computer.
• Processors can be classified based on:
  • Technology (Dual-core, Quad-core, Octa-core, etc.)
  • Manufacturer (such as Intel and AMD)

Speed of processors is usually measured in megahertz (MHz) – millions of instructions per second; and gigahertz (GHz) – billions of instructions per second, is indicative of its power.

Power Supply Unit (SMPS)

• The Power Supply Unit provides electrical power to all parts of the system.
• It converts AC (Alternating Current) from home or office supply into DC (Direct Current).

Random Access Memory (RAM)

• RAM is a very important part of a computer system that affects its performance.
• When the computer starts, the operating system is loaded into RAM.
• Any program that is currently running must also be loaded into RAM.
• RAM provides temporary storage for active programs and data.
• Modern computers usually have 8 GB to 32 GB RAM or more.

Hard Disk (HD)

• The hard disk is a secondary storage device used for permanent data storage.
• It stores all data, including files saved in the C drive.
• Programs are first stored on the hard disk and then transferred to RAM for execution.
• Capacity of a hard disk is expressed in terms of Gigabytes, Terabytes.

Pen Drive / Flash Drive

• It is a small pen-like storage device and very compact in size.
• It can be accessed by directly inserting in the USB(Universal Serial Bus) Port.
• It is widely used due to its small size, portability, and easy accessibility.

Memory Units

• Data stored in binary (0s and 1s)
• 1 Nibble = 4 bits
• 1 Byte = 8 bits
• 1024 Bytes = 1 KB
• 1024 KB = 1 MB
• 1024 MB = 1 GB
• 1024 GB = 1 TB
• 1024 TB = 1 PB
• 1024 PB = 1 EB
• 1024 EB = 1 ZB
• 1024 ZB = 1 YB

Optical Storage Devices

• CD (Compact Disc)
• DVD (Digital Video Disc)
• DVD has higher storage capacity than CD
• Accessed using disc drive

Session-3: Operating System

Operating System

• An operating system (OS) is system software that acts as an interface between the user and computer hardware.
• It helps the computer communicate between hardware and software components.
• It manages and controls the overall functioning of the computer system.
• Some popular operating systems are: Windows, Linux, Unix, MS-DOS, Solaris, and macOS.
• It performs important tasks such as:
  • Accepting input from input devices
  • Displaying output on screen or other devices
  • Managing files and folders
  • Controlling hardware devices
  • Installing and uninstalling peripheral devices
  • Ensuring smooth coordination between all components

Functions of Operating System

Communication Manager

• Manages communication with hardware devices
• Uses device drivers

Resource Management

• Allocates resources like CPU, memory, files, I/O devices

Process Management

• Controls execution of processes
• Decides process scheduling

Memory Management

• Allocates and frees memory for processes

File Management

• Manages files and folders
• Includes create, delete, copy, move, rename

Types of Operating System

• Single-tasking OS: Runs only one program at a time
• Multi-tasking OS: Runs multiple programs simultaneously
• Single-user OS: Supports one user at a time (desktop systems)
• Multi-user OS: Supports multiple users simultaneously
• Real-time OS: Responds within strict time limit, Used in critical systems (e.g., missile systems)
• Batch Processing OS: Processes data in batches, Reduces setup time for similar tasks

Session-4: Troubleshooting and Utilities

Common Troubleshooting Steps

• Close unused programs
• Check hardware cables and connections
• Ensure devices are powered ON
• Repeat steps before issue occurred
• Press F1 for Help window
• Record error messages
• Restart device/system if needed

Hardware Troubleshooting

Monitor Not Displaying

• Check sleep mode
• Check power and cable connections
• Charge laptop battery if needed

Keyboard Issues

• Check connection
• Check physical damage
• Replace batteries (wireless)
• Clean stuck keys

Mouse Issues

• Check connection
• Inspect damage
• Restart wireless mouse
• Clean mouse surface

Printer Problems

• Check power and connection
• Load paper
• Fix paper jam
• Replace ink cartridge
• Install correct driver
• Check network/IP communication

Print sent to wrong printer

• Change default printer via:
  • Control Panel → Devices and Printers
• Set correct printer as default

Printer slow

• Reduce print quality
• Use Fast Draft mode

Sound Troubleshooting

• Check volume level
• Check media player settings
• Verify cable connections
• Test with headphones
• If headphones work → speaker issue

Software Troubleshooting

Application Slow – Check for updates

Application Frozen

• Forcefully End the Application by opening task manager by pressing Ctrl+Alt+Delete
• End task and restart
• Restart system if needed
• Perform hard reboot if required (may cause data loss)
• Run antivirus scan

Utilities

Utilities are the special programs that help computer systems to work more smoothly, efficiently and effectively. Utility software programs help in:

• improving the performance of computer
• provide security from virus,
• manage disk space
• free disk space on hard Disk – provide backup etc.

Disk Cleanup

We can use Disk Cleanup utility to get some more space for smooth functioning of computer as sometimes due to non-availability of free space slows the functioning of the computer. There should be at least 200-500MB of free hard drive space on your system.

• Right click C drive → Properties → Disk Cleanup
• Remove system files
• Delete temporary files

Empty Recycle Bin

• Right click → Empty Recycle Bin

Remove Temporary Files

• Use Disk Cleanup tool
• Delete temporary internet files

Disk Defragmentation

• Optimizes file storage
• Reduces gaps in disk
• Improves system speed
• Steps:
  • Open C drive → Properties → Tools → Optimize → Select drive → Optimize

Networking Troubleshooting

No Internet Connection

• Check network icon status
• Use Network & Sharing Center → Troubleshoot

Check IP Address

• Open CMD Prompt → Type: IPCONFIG → Shows IP details if connected

Network Cable Issue (Fly Lead)

• Check cable connection
• Seek network administrator help

Network Card Issue

• Check indicator lights
• Replace if damaged