Unit 1: Computer Fundamentals and Data Representation - Subjective Questions

A computer is an electronic device that accepts data as input, processes it according to a set of stored instructions (program), and produces meaningful information as output while having the ability to store data for future use.

Main characteristics of a computer:

• Speed: Computers can perform millions to billions of operations per second. Operation times are measured in milliseconds (), microseconds (), nanoseconds (), and picoseconds ().
• Accuracy: Computers produce highly accurate results. Errors are usually due to incorrect input or faulty programs (GIGO - Garbage In, Garbage Out), not the machine.
• Diligence: A computer can perform repetitive tasks without fatigue, boredom, or loss of concentration.
• Versatility: A single computer can perform a wide variety of tasks such as playing music, editing documents, and performing calculations.
• Storage Capacity: Computers can store huge amounts of data and retrieve it whenever required.
• Automation: Once a program is loaded, a computer can work automatically without human intervention.
• Reliability: Computers give consistent results over long periods of operation.

Computers have evolved through five generations, each defined by major technological advancements:

• First Generation (1940–1956) – Vacuum Tubes:

  • Used vacuum tubes for circuitry and magnetic drums for memory.
  • Very large, generated a lot of heat, and consumed huge power.
  • Used machine language. Example: ENIAC, UNIVAC.

• Second Generation (1956–1963) – Transistors:

  • Transistors replaced vacuum tubes; smaller, faster, cheaper.
  • Used assembly language and early high-level languages (COBOL, FORTRAN).
  • Example: IBM 1401.

• Third Generation (1964–1971) – Integrated Circuits (ICs):

  • Transistors were miniaturized onto silicon chips.
  • Introduced keyboards, monitors, and operating systems.
  • Example: IBM 360.

• Fourth Generation (1971–Present) – Microprocessors:

  • Thousands of ICs built onto a single chip (VLSI).
  • Birth of personal computers and GUIs.
  • Example: Intel 4004, IBM PC.

• Fifth Generation (Present & Beyond) – Artificial Intelligence:

  • Based on AI, parallel processing, and ULSI technology.
  • Focus on voice recognition, robotics, and natural language processing.

The block diagram of a computer shows the flow of data and control among its functional units.

    +----------------+
    |  Input Unit    |
    +----------------+
            |
            v

            v
    +----------------+
    |  Output Unit   |
    +----------------+

Functions of each unit:

• Input Unit: Accepts data and instructions from the user and converts them into machine-readable form. Examples: keyboard, mouse, scanner.
• Central Processing Unit (CPU): The brain of the computer, consisting of:
  • Arithmetic Logic Unit (ALU): Performs arithmetic (addition, subtraction) and logical (comparison) operations.
  • Control Unit (CU): Directs and coordinates all operations by generating control signals; fetches, decodes, and executes instructions.
• Memory Unit: Stores data, instructions, and results. Divided into primary memory (RAM, ROM) and secondary memory (hard disk).
• Output Unit: Converts processed data into human-readable form. Examples: monitor, printer.

Both CU and ALU are key components of the CPU but perform different functions:

In summary:

• The CU tells other components what to do and when.
• The ALU does the actual computation and logic work.

Information Technology has transformed nearly every sector of society:

• Education: E-learning platforms, online examinations, virtual classrooms, digital libraries, and smart boards.
• Healthcare: Electronic health records, telemedicine, medical imaging (MRI, CT scans), robotic surgery, and hospital management systems.
• Banking & Finance: ATMs, online banking, UPI, mobile wallets, fraud detection, and stock trading.
• Business & Commerce: E-commerce (Amazon, Flipkart), inventory management, CRM, and digital marketing.
• Government (e-Governance): Online tax filing, digital identity (Aadhaar), passport services, and public grievance systems.
• Entertainment: Streaming services, gaming, animation, and virtual reality.
• Transportation: GPS navigation, online ticket booking, traffic management, and ride-sharing apps.
• Agriculture: Weather forecasting, precision farming, and market price information systems.
• Industry/Manufacturing: Automation, robotics, CAD/CAM, and supply chain management.

IT improves efficiency, accuracy, speed, and accessibility across all these domains.

A number system defines how numbers are represented using a set of symbols. Four common number systems are used in computing:

• Binary Number System:

  • Base =
  • Symbols:
  • Used internally by all digital computers.

• Octal Number System:

  • Base =
  • Symbols: to
  • Used as a shorthand for binary (groups of 3 bits).

• Decimal Number System:

  • Base =
  • Symbols: to
  • The number system used by humans in daily life.

• Hexadecimal Number System:

  • Base =
  • Symbols: to and (where )
  • Used as a compact way to represent binary (groups of 4 bits), common in memory addresses.

The value of a digit depends on its position (positional weight) relative to the base.

We convert to other bases using repeated division.

Decimal to Binary (divide by 2):

Reading remainders bottom to top:

Decimal to Octal (divide by 8):

So

Decimal to Hexadecimal (divide by 16):

So

In the binary system, each digit has a positional weight that is a power of , starting from at the rightmost position.

Binary number:

Therefore, .

Positional weight method: Multiply each binary digit by its positional weight () and add the products to get the decimal value.

Procedure (Binary to Octal):

• Since , each octal digit corresponds to exactly 3 binary bits.
• Group the binary digits into sets of 3 bits, starting from the right (least significant bit).
• Add leading zeros to the leftmost group if needed.
• Convert each 3-bit group to its octal equivalent.

Conversion of :

Group into 3 bits from the right:

Convert each group:

Therefore, .

Procedure (Binary to Hexadecimal):

• Since , each hexadecimal digit corresponds to exactly 4 binary bits.
• Group the binary digits into sets of 4 bits, starting from the right.
• Add leading zeros to the leftmost group if required.
• Convert each 4-bit group into its hexadecimal equivalent (remember ).

Conversion of :

Group into 4 bits from the right:

Convert each group:

Therefore, .

Hexadecimal to Decimal:

Each hex digit has a positional weight that is a power of . Note , .

So .

Hexadecimal to Binary:

Convert each hex digit to its 4-bit binary equivalent:

Combine the groups:

Dropping leading zeros: .

Octal to Decimal:

Each octal digit has a positional weight that is a power of .

So .

Octal to Binary:

Convert each octal digit into its 3-bit binary equivalent:

Combine the groups:

Memory in a computer is broadly divided into primary and secondary memory:

Key point:

• Primary memory provides fast, temporary working storage for the CPU.
• Secondary memory provides large, permanent storage for data and programs not currently in use.

The IPO cycle describes the fundamental working of a computer in three stages:

• Input Stage:

  • Raw data and instructions are entered through input devices (keyboard, mouse, scanner).
  • Data is converted into machine-readable (binary) form.

• Processing Stage:

  • The CPU processes the data using the ALU and Control Unit.
  • Instructions are fetched from memory, decoded, and executed.
  • Intermediate results are stored in memory.

• Output Stage:

  • Processed data (information) is converted back into human-readable form.
  • It is displayed or produced through output devices (monitor, printer).

Storage supports the cycle by holding data and instructions before, during, and after processing.

Example: When calculating :

• Input: numbers 5 and 3 entered
• Process: ALU adds them
• Output: result 8 is displayed

Binary Addition Rules: , , (write 0, carry 1), (write 1, carry 1).

(a) :

1011

• 1101

  11000

Step by step (right to left):

• → write 0, carry 1
• → write 0, carry 1
• → write 0, carry 1
• → write 1, carry 1
• final carry 1

Result: . Check: . ✓

Binary Subtraction Rules: , , , with borrow.

(b) :

1101

• 0110

  0111

Result: . Check: . ✓

These are the basic units used to measure and represent data in computers:

• Bit (Binary Digit):

  • The smallest unit of data, having a value of either or .
  • All data in a computer is ultimately stored as bits.

• Nibble:

  • A group of 4 bits.
  • One nibble can represent a single hexadecimal digit ( to ).

• Byte:

  • A group of 8 bits (2 nibbles).
  • Standard unit for representing a single character; can store different values.

• Word:

  • A group of bits processed by the CPU as a single unit.
  • Word size depends on the processor architecture (e.g., 16-bit, 32-bit, 64-bit).

Higher units: , , .

A fractional decimal number is converted in two parts: the integer part by repeated division, and the fractional part by repeated multiplication.

Integer part – divide by 2:

Reading bottom to top:

Fractional part – multiply by 2:

Reading top to bottom:

Combined result:

Computers can be classified based on the type of data they process:

Note: A hybrid computer combines features of both analog and digital computers, often used in specialized applications like medical equipment (e.g., ICU monitors).

Coding schemes are standards used to represent characters (letters, digits, symbols) in binary form.

ASCII (American Standard Code for Information Interchange):

• A 7-bit coding scheme (extended to 8 bits) used to represent characters.
• 7-bit ASCII can represent characters; extended ASCII represents characters.
• Includes uppercase/lowercase letters, digits, punctuation, and control characters.
• Example: The letter A = in decimal = .
• Limitation: Cannot represent characters of many world languages.

Unicode:

• A universal coding scheme designed to represent characters of all languages in the world.
• Uses up to 16 bits or more, allowing over 1 million unique characters.
• Backward compatible with ASCII (first 128 codes are the same).
• Common encodings: UTF-8, UTF-16, UTF-32.
• Widely used on the internet and modern software for multilingual support.

Key difference: ASCII is limited to English characters, while Unicode supports virtually all writing systems globally.

There is no direct octal-to-hexadecimal method, so we use binary as an intermediate number system.

Step 1: Octal to Binary (each octal digit → 3 bits):

So

Step 2: Binary to Hexadecimal (group into 4 bits from the right):

(Added leading zeros to the leftmost group.)

Convert each group:

Therefore, .

Verification (via decimal): ; . ✓