Computer System Chapter Notes | Informatics Practices for Class 11 - Humanities/Arts PDF Download

Introduction to Computer System

• A computer processes input data according to given instructions to produce desired output.
• It transforms data into information, which, upon further analysis and interpretation, yields knowledge.
• A computer system comprises four main physical components: CPU, primary memory, input devices, and output devices, collectively referred to as hardware.
• The concept of intelligence in computers is highlighted by the quote: "A computer would deserve to be called intelligent if it could deceive a human into believing that it was human."

Central Processing Unit (CPU)

• The CPU is the electronic circuitry responsible for processing and is often called the brain of the computer.
• It is commonly referred to as a processor and is physically implemented on one or more microchips called integrated circuits (ICs) made of semiconductor materials.
• The CPU executes instructions and processes data from programs by fetching them from memory, performing arithmetic and logical operations, and storing results back in memory.
• It contains registers, which are small, fast local memory units within the CPU chip used to store data, instructions, or intermediate results; registers are limited in size and number.
• The CPU consists of two main components: the Arithmetic Logic Unit (ALU) and the Control Unit (CU).
• The ALU performs all arithmetic and logical operations required by a program’s instructions.
• The CU manages sequential instruction execution, interprets instructions, and directs data flow among the computer’s memory, ALU, and input/output devices.
• The CPU is also known as a microprocessor.

Input Devices

• Input devices send control signals to a computer, converting input data into a digital format acceptable by the computer system.
• Examples include keyboards, mice, scanners, touch screens, and specially designed braille keyboards for the visually impaired.
• Voice input is also possible, such as using Google voice search to input search strings via voice.
• Data entered through input devices is temporarily stored in the main memory (RAM) and can be permanently stored in secondary memory for future use.

Output Devices

• Output devices receive data from a computer system for display or physical production, converting digital information into a human-understandable form.
• Examples include monitors, projectors, headphones, speakers, and printers.
• Braille display monitors assist visually challenged individuals in understanding textual output.
• Printers produce physical (hardcopy) outputs, with common types being inkjet, laserjet, and dot matrix printers.
• 3D printers create physical replicas of digital 3D designs and are used in manufacturing for prototypes and in medical fields for developing body organs.

Evolution of Computer

• Computing devices have evolved from simple calculators to powerful data processors in a short time.
• Pascaline, invented by Blaise Pascal, was a mechanical calculator for addition, subtraction, multiplication, and division through repeated operations.
• The Von Neumann architecture includes a CPU for processing, memory for storing data and programs, input/output devices, and communication channels.
• The Electronic Numerical Integrator And Computer (ENIAC) was the first binary programmable computer based on Von Neumann architecture.
• In the 1970s, Large Scale Integration (LSI) enabled the integration of a complete CPU on a single chip, called a microprocessor.
• Moore’s Law, introduced in 1965 by Gordon Moore, predicted that the number of transistors on a chip would double every two years while costs halved.
• In the 1980s, Very Large Scale Integration (VLSI) integrated around 3 million components on a small chip, exponentially increasing processing power.
• Super Large Scale Integration (SLSI) further advanced technology, allowing approximately 106 components on a single IC.
• IBM introduced its first personal computer (PC) in 1981, and Apple launched Macintosh machines in 1984.
• The introduction of Graphical User Interfaces (GUIs) by Microsoft and others replaced command-line interfaces like UNIX and DOS, boosting PC popularity.
• The 1990s saw the growth of the World Wide Web (WWW), accelerating widespread computer use.
• Laptops made personal computing portable, followed by smartphones, tablets, and personal digital assistants leveraging processor miniaturization, faster memory, and high-speed connectivity.
• The next wave includes wearable gadgets like smartwatches, lenses, headbands, and headphones, and smart appliances integrated into the Internet of Things (IoT) using artificial intelligence.

Computer Memory

• A computer system requires memory to store data and instructions for processing, typically referring to primary memory, with secondary memory used for permanent storage.
• Memory uses binary numbers (bits, 0s, and 1s) as the basic units.
• A 4-bit word is called a nibble (e.g., 1001, 1010).
• An 8-bit word, or two nibbles, is called a byte (e.g., 01000110, 01111100).
• Bytes are grouped into larger units: 1 KB = 1024 bytes, 1 MB = 1024 KB, 1 GB = 1024 MB, 1 TB = 1024 GB, 1 PB = 1024 TB, 1 EB = 1024 PB, 1 ZB = 1024 EB, 1 YB = 1024 ZB.

Types of Memory

• Computers have two main memory types: primary memory and secondary memory, analogous to human short-term and long-term memory.

Primary Memory

• Primary memory is essential for a computer system, where programs and data are loaded before processing.
• The CPU directly interacts with primary memory for read/write operations.
• It includes two types: Random Access Memory (RAM) and Read-Only Memory (ROM).
• RAM is volatile, retaining data only while the computer is powered; it is wiped when power is off.
• RAM is used to temporarily store data during computer operation and is loaded with programs and data when the computer starts or software is launched.
• RAM, often called main memory, is faster than secondary memory or storage devices.
• ROM is non-volatile, retaining contents even without power, and is used for small, permanent storage of rarely changed data, such as the boot loader that loads the operating system into RAM.

Cache Memory

• Cache memory is a very high-speed memory placed between the CPU and primary memory to speed up CPU operations.
• It stores copies of frequently accessed primary memory data, reducing the average time to access data.
• The CPU first checks the cache for data; if found, it reads from the cache; otherwise, it accesses primary memory.

Secondary Memory

• Secondary memory is non-volatile, has a larger storage capacity than primary memory, and is used for permanent data storage.
• It is slower and cheaper than primary memory and cannot be directly accessed by the CPU; data must be transferred to primary memory first.
• Examples include Hard Disk Drives (HDDs), CDs/DVDs, memory cards, and Solid-State Drives (SSDs), which offer faster data transfer than HDDs.
• Portable flash/pen drives simplify data transfer between computers.

Data Capturing, Storage, and Retrieval

• Data processing involves capturing data, storing it in files or databases, and retrieving it for further actions.

Data Capturing

• Data capturing involves gathering data from various sources in digital form, using devices like keyboards, barcode readers, or sensors on satellites.
• Social media comments are also captured as data.
• Heterogeneity among data sources can make capturing complex.

Data Storage

• Data storage involves saving captured data for later processing, which is challenging due to the high rate of data production.
• Decreased costs of digital storage devices have simplified storage tasks.
• Large organizations use data servers with large, fast storage to process vast amounts of data efficiently, though setup and maintenance costs are high.
• Storage devices require periodic upgrades as data volume increases.

Data Retrieval

• Data retrieval involves fetching data from storage devices for processing based on user requirements.
• As databases grow, minimizing data access time is crucial for faster processing.

Data Deletion and Recovery

• Data deletion is a major threat, as storage devices can malfunction, crash, or be affected by accidental erasure or malicious hacking/malware.
• Deleting data digitally involves changing bit-level details, which is time-consuming; instead, deleted data’s address is marked as free, showing the space as empty without actual deletion.
• Data recovery is possible if the deleted memory space has not been overwritten.
• Security concerns include unauthorized deletion, preventable by limiting system access, using passwords, and encrypting files.
• Unwanted data recovery by unauthorized users is a risk when discarding old storage devices without properly shredding data, posing a threat to data confidentiality.

Software

• Software is a set of instructions that operates computer hardware, which cannot function independently.
• Software is intangible, comprising instructions and data processed using hardware to complete tasks.
• Examples include operating systems (e.g., Ubuntu, Windows), word processors (e.g., LibreOffice Writer, Microsoft Word), video players (e.g., VLC), and photo editors (e.g., Paint, LibreOffice Draw).
• A softcopy is a document or image stored digitally, while a hardcopy is its printed form.
• Hardware includes physical components like RAM, keyboards, printers, monitors, and CPUs.

Need of Software

• Software makes computer hardware useful and operational by enabling communication between hardware components and the end user.
• It acts as an interface, allowing users to instruct hardware indirectly.
• Software is classified into three categories based on interaction with hardware and functions: system software, programming tools, and application software.

System Software

• System software provides basic functionality to operate a computer by directly interacting with hardware.
• It operates and uses hardware components and provides services to end users or other software.
• Examples include operating systems, system utilities, and device drivers.

Operating System

• An operating system is the most essential system software, required for other software to function.
• It manages application programs, provides user access, and ensures system security.
• Examples include Windows, Linux, Macintosh, Ubuntu, Fedora, Android, and iOS.

System Utilities

• System utilities are software for computer maintenance and configuration.
• Some are included with the operating system, such as disk defragmentation tools, formatting utilities, and system restore utilities.
• Others, like antivirus software, disk cleaners, and disk compression software, are not included but enhance system performance.

Device Drivers

• Device drivers ensure proper functioning of specific devices by acting as an interface between the device and the operating system.
• They manage device operations at the hardware level, as the operating system alone cannot handle all peripherals’ diverse characteristics.
• Drivers hide hardware-level operation details, providing required services like a language translator.

Application Software

• Application software runs on top of system software to meet diverse user requirements.
• It is divided into general-purpose and customized application software.
• A computer can function without application software but not without system software.

General Purpose Software

• General-purpose software is developed for generic applications to serve a broad audience.
• Users can use it based on their needs, e.g., LibreOffice Calc for calculations or account sheets.
• Examples include Adobe Photoshop, GIMP, Mozilla web browser, and iTunes.

Customised Software

• Customized software is tailor-made for specific organizations or individuals to meet unique requirements.
• It is designed to suit specific needs, similar to custom-stitched clothing.
• Examples include websites, school management software, and accounting software.

Proprietary or Free and Open Source Software

• Free and Open Source Software (FOSS) allows public use and access to source code for collaborative improvement, e.g., Ubuntu, Python, LibreOffice, OpenOffice, and Mozilla Firefox.
• Freeware is freely available for use but may not include source code, e.g., Skype, Adobe Reader.
• Proprietary software is purchased from vendors holding copyrights, e.g., Microsoft Windows, Tally, QuickHeal.
• Software classification as freeware, open source, or proprietary depends on the developer’s terms and conditions.