Unit 1: Computer fundamentals and number systems
Information Technology notes · PTU syllabus (BSIT104/BSBC104)
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Unit summary
Every IT professional needs to know how a computer is organised and how it represents numbers. This unit covers the block structure of a computer, its characteristics, generations and classification, and the binary, decimal, octal and hexadecimal number systems, conversions between them and binary arithmetic.
After this unit you can
- Draw and explain the block structure of a computer
- Explain characteristics, generations and classification of computers
- Convert between number systems
- Perform binary arithmetic
PTU syllabus topics
- Block structure of a computer
- characteristics
- generations and classification of computers
- bit/byte/binary/decimal/hexadecimal/octal systems and conversions
- binary arithmetic
Decimal to binary
Divide by 2, read remainders upward
Binary to decimal
Σ bit × 2^position
Binary to octal
Group 3 bits from the right
Binary to hex
Group 4 bits from the right
Example
(13)₁₀ = (1101)₂ = (15)₈ = (D)₁₆
Topic 1
Block structure of a computer
- 1Input unit
Accepts data and instructions
- 2Memory unit
Stores data and programs
- 3Control unit
Directs and coordinates all operations
- 4Arithmetic logic unit
Performs calculations and comparisons
- 5Output unit
Presents results
The CPU = control unit + ALU (+ registers).
Topic 2
Characteristics of computers
Characteristics: speed, accuracy, storage, diligence (no fatigue), versatility and automation; limitations: no intelligence of its own and no feelings. Business applications: accounting (Tally), payroll, inventory, banking and ATMs, online shopping, customer relationship management, data analysis and communication.
Topic 3
Generations of computers
| Generation | Technology | Examples and features |
|---|---|---|
| First (1940–1956) | Vacuum tubes | ENIAC, UNIVAC — huge, hot, machine language |
| Second (1956–1963) | Transistors | IBM 1401 — smaller, assembly language, batch processing |
| Third (1964–1971) | Integrated circuits | IBM 360 — keyboards, monitors, operating systems |
| Fourth (1971–present) | Microprocessors (VLSI) | Personal computers, laptops, networks, GUI |
| Fifth (present and beyond) | AI, parallel processing, ULSI | Natural language, machine learning, quantum research |
Topic 4
Classification of computers
By data handled
Analog, digital, hybrid
By size and power
Supercomputer (PARAM, weather forecasting), mainframe (banks), minicomputer (servers), microcomputer (desktops, laptops, tablets, smartphones)
By purpose
General-purpose, special-purpose (embedded systems)
Topic 5
Number systems and conversions
| System | Base | Digits |
|---|---|---|
| Binary | 2 | 0, 1 |
| Octal | 8 | 0–7 |
| Decimal | 10 | 0–9 |
| Hexadecimal | 16 | 0–9, A–F |
Decimal to binary
Divide by 2 repeatedly; read remainders bottom-up
Binary to decimal
Multiply each bit by 2^position and add
Binary to octal
Group bits in threes from the right
Binary to hexadecimal
Group bits in fours from the right
Example
(25)₁₀ = (11001)₂ = (31)₈ = (19)₁₆.
Topic 6
Binary arithmetic
Addition
0 + 0 = 0; 0 + 1 = 1; 1 + 1 = 10 (carry 1); 1 + 1 + 1 = 11
Subtraction
1 − 0 = 1; 1 − 1 = 0; 0 − 1 = 1 with borrow 1
Multiplication
0 × 0 = 0; 1 × 1 = 1; shift and add
2's complement
Invert all bits and add 1
Example
1011 + 0110 = 10001 (11 + 6 = 17). 1101 − 0110: 2's complement of 0110 is 1010; 1101 + 1010 = 10111; drop the carry → 0111 (13 − 6 = 7).
Key terms
- ALU
- Arithmetic logic unit that performs calculations and comparisons
- Microprocessor
- CPU on a single chip
- Supercomputer
- Fastest class of computer for complex calculations
- Hexadecimal
- Base-16 number system
- 2's complement
- Method of representing negative binary numbers
Quick revision
- Input, CPU (ALU, CU, registers), memory, output.
- Speed, accuracy, storage, automation, versatility, diligence.
- Five generations; analog, digital, hybrid; super, mainframe, mini, micro.
- Binary, octal, decimal, hexadecimal conversions.
- Binary addition, subtraction, 2's complement.
Important exam questions
Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).
Short-answer questions
- Q1.Draw the block diagram of a computer.
- Q2.State four characteristics of computers.
- Q3.Name the technology of each computer generation.
- Q4.Convert (45)₁₀ to binary.
- Q5.Convert (1A)₁₆ to decimal.
- Q6.Find the 2's complement of 0101.
Long-answer questions
- Q1.Explain the block structure of a computer.
- Q2.Explain the generations and classification of computers.
- Q3.Explain number systems and conversions with examples.
- Q4.Explain binary arithmetic with examples.
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