BCA 205T Computer Organization and Architecture Notes cover all 4 units of the GGSIPU BCA Semester 3 paper in 72 pages, from Boolean algebra to virtual memory, with 36 solved examples, 20 quick numericals, 51 labelled figures and 66 exam questions. They follow the syllabus for the batch admitted in 2024-25 onwards.
Scheme: BCA w.e.f. 2024-25 | Applies to: 2024-25 batch onwards | Verified against: BCA Scheme and Syllabus, 01 Aug 2025
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BCA 205T Computer Organization and Architecture at a glance: GGSIPU BCA Sem 3 credits, units and exam pattern
BCA 205T is a core theory paper of the GGSIPU BCA programme that runs from logic gates to the CPU, I/O and memory. It sits with the other GGSIPU BCA Semester 3 papers.
| Code and title | BCA 205T, Computer Organization and Architecture |
|---|---|
| Course and semester | BCA, Semester 3 |
| Category and credits | Core Course Theory (CCT), 4 credits, 4 lecture hours a week |
| Marks | 100: 40 internal + 60 end-term |
| Applies to | Batch admitted in 2024-25 onwards |
| End-term pattern | Q1 compulsory: 10 short questions of 2 marks, at least 2 per unit. Then one 10-mark question per unit, from a choice of two (20 + 40 = 60 marks) |
| Units | 4 units, 11 hours each |
| Paired lab | BCA 205P, CCP, 1 credit, 100 marks (40 + 60) |
The BCA 205T scheme says grading follows GGSIPU Ordinance 11, which also sets re-appear rules.
BCA 205T Computer Organization and Architecture Notes unit-wise: 36 solved examples and 66 exam questions across 4 units
Other BCA papers sit under GGSIPU BCA notes.
BCA 205T Unit 1: Boolean Algebra, Logic Gates and Combinational Circuits
Boolean laws and De Morgan's theorems, the seven gates (NAND and NOR as universal), SOP, POS and K-maps with don't care cells, then adders, subtractors, the 4-bit adder-subtractor, MUX, DEMUX, decoder and priority encoder.
Pages 3 to 21 · 16 solved examples · 8 two-mark and 8 ten-mark questions
| Stage | A + B + carry | Sum | Carry |
|---|---|---|---|
| FA0 | 1 + 0 + 0 | 1 | 0 |
| FA1 | 1 + 1 + 0 | 0 | 1 |
| FA2 | 0 + 1 + 1 | 0 | 1 |
| FA3 | 1 + 0 + 1 | 0 | 1 |
Quick look: adding 1011 and 0110 on a 4-bit parallel adder (from page 15)
- Stage
- FA0
- A + B + carry
- 1 + 0 + 0
- Sum
- 1
- Carry
- 0
- Stage
- FA1
- A + B + carry
- 1 + 1 + 0
- Sum
- 0
- Carry
- 1
- Stage
- FA2
- A + B + carry
- 0 + 1 + 1
- Sum
- 0
- Carry
- 1
- Stage
- FA3
- A + B + carry
- 1 + 0 + 1
- Sum
- 0
- Carry
- 1
Result: 1 0001 = 17.
BCA 205T Unit 2: Sequential Circuits, Shift Registers and Counters
NOR and NAND latches, clocked SR, D, JK and T flip-flops with excitation tables, the race around condition and the master-slave fix, three flip-flop conversions, four shift register types, and ripple, synchronous and MOD-N counters.
Pages 22 to 37 · 7 solved examples · 8 quick numericals · 8 two-mark and 9 ten-mark questions
Quick look: a MOD-10 ripple counter in four steps (from page 35)
- 23 = 8 is too small and 24 = 16 is enough, so 4 flip-flops.
- 10 = 1010, so Q3 = 1 and Q1 = 1.
- Q3 and Q1 drive a NAND gate wired to CLR of every flip-flop.
- At 1010 the NAND goes LOW and the count clears to 0000.
BCA 205T Unit 3: Data Transfer Operations and Basic Computer Organization
RTL (P : R2 ← R1), bus and memory transfer, arithmetic, logic and shift micro-operations, the instruction cycle flowchart, 14-bit control words, stacks with Reverse Polish Notation, four instruction formats and addressing modes.
Pages 38 to 54 · 6 solved examples · 7 quick numericals · 8 two-mark and 8 ten-mark questions
| Mode | Effective address | Typical use |
|---|---|---|
| Register indirect | Contents of the register | Pointers |
| Relative | PC + address field | Branches |
| Indexed | XR + address field | Arrays |
| Base register | Base register + address field | Relocation |
Quick look: effective address in four addressing modes (from page 52)
- Mode
- Register indirect
- Effective address
- Contents of the register
- Typical use
- Pointers
- Mode
- Relative
- Effective address
- PC + address field
- Typical use
- Branches
- Mode
- Indexed
- Effective address
- XR + address field
- Typical use
- Arrays
- Mode
- Base register
- Effective address
- Base register + address field
- Typical use
- Relocation
BCA 205T Unit 4: Input-Output Organization and Memory Organization
Part A: I/O interfaces, strobe and handshaking, programmed and interrupt I/O, priority interrupts and DMA. Part B: the memory hierarchy, RAM and ROM address maps, disks, associative memory, cache mapping and virtual memory with page replacement.
Pages 55 to 72 · 7 solved examples · 5 quick numericals · 8 two-mark and 9 ten-mark questions
Quick look: average access time with a cache (from page 67)
Tavg = h × Tc + (1 - h) × Tm
= 0.9 × 100 + 0.1 × 1000
= 190 ns (h = 0.9, Tc = 100 ns, Tm = 1000 ns)Instruction codes and basic computer registers in computer organisation: excerpt from page 44 of the BCA 205T notes
Excerpt from page 44
The basic computer
To show how a real computer works, M. Morris Mano designed a simple "basic computer". It has a memory of 4096 words of 16 bits each, eight registers, a common bus and 25 instructions. Instruction codes, registers and the instruction cycle are all explained on this one machine.
Instruction codes
A program is a set of instructions, and each instruction is stored in memory as a binary instruction code. The code is divided into parts:
- Operation code (opcode): what to do, such as add, load or store. With n opcode bits, up to 2n different operations are possible.
- Address (operand) field: where the operand is, usually a memory address or a register.
This is John von Neumann's stored program concept: instructions and data are kept in the same memory, and the control unit fetches and executes the instructions one by one. A memory of 4096 words needs 12 address bits (212 = 4096). Of the 4 bits left in a 16-bit word, 3 form the opcode and 1 is the mode bit I.
Direct and indirect address
- Immediate: the address field contains the operand itself.
- Direct address (I = 0): the address field contains the address of the operand.
- Indirect address (I = 1): the address field contains the address of a memory word that holds the operand's address, so one extra memory access is needed.
The address finally used to reach the operand is called the effective address (EA).
Computer registers
The register sizes follow from the memory size: addresses are 12 bits and data words are 16 bits.
| Symbol | Bits | Register name | Function |
|---|---|---|---|
| DR | 16 | Data register | Holds the memory operand |
| AR | 12 | Address register | Holds the address for memory |
| AC | 16 | Accumulator | Processor register that holds results |
| IR | 16 | Instruction register | Holds the instruction code being executed |
| PC | 12 | Program counter | Holds the address of the next instruction |
| TR | 16 | Temporary register | Holds temporary data |
| INPR | 8 | Input register | Holds an input character |
| OUTR | 8 | Output register | Holds an output character |
Registers of the basic computer (excerpt, page 44)
- Symbol
- DR
- Bits
- 16
- Register name
- Data register
- Function
- Holds the memory operand
- Symbol
- AR
- Bits
- 12
- Register name
- Address register
- Function
- Holds the address for memory
- Symbol
- AC
- Bits
- 16
- Register name
- Accumulator
- Function
- Processor register that holds results
- Symbol
- IR
- Bits
- 16
- Register name
- Instruction register
- Function
- Holds the instruction code being executed
- Symbol
- PC
- Bits
- 12
- Register name
- Program counter
- Function
- Holds the address of the next instruction
- Symbol
- TR
- Bits
- 16
- Register name
- Temporary register
- Function
- Holds temporary data
- Symbol
- INPR
- Bits
- 8
- Register name
- Input register
- Function
- Holds an input character
- Symbol
- OUTR
- Bits
- 8
- Register name
- Output register
- Function
- Holds an output character
The registers and memory are connected to a 16-bit common bus. Three select lines S2 S1 S0 choose which unit places its data on the bus, and each register has the control inputs LD (load), INR (increment) and CLR (clear).
How to write BCA 205T answers: truth tables, K-map groups, timing diagrams and RTL steps
A BCA 205T ten-mark answer is drawn as much as written. The notes' exam tips repeat one idea: show every working part, because step marks are given part by part.
Circuit questions (Unit 1). Write four parts in order: definition, truth table, Boolean expression (with the K-map if asked) and a labelled logic diagram. The notes name a missing diagram as the most common reason for losing marks. On a K-map, mark each group and write its term beside it.
Flip-flop and counter questions (Unit 2). Draw the circuit, the state table and the timing diagram. In a MOD-N design, show 2n ≥ N and the binary of N first, because the NAND connections come from it. In a flip-flop conversion, marks go to the conversion table, the K-maps, the expressions and the diagram.
Register transfer questions (Unit 3). Put the timing signal before each micro-operation and use the arrow ←. The notes warn that examiners treat AR = PC as wrong notation.
Memory numericals (Unit 4). For cache, memory-map or paging sums, write how many bits each field needs, then draw the address split as a box. The split earns step marks even if the final number slips.
Worked example: fetch and decode in RTL (from page 53)
T0: AR ← PC
T1: IR ← M[AR], PC ← PC + 1
T2: D0-D7 ← Decode IR(12-14), AR ← IR(0-11), I ← IR(15)Each line starts with its timing signal and uses only arrows, and every register named matches the basic computer's register list. A two-mark fetch question needs T0 and T1; a ten-mark instruction cycle answer adds T2, the flowchart and a line on how D7 and I decide the instruction type.
Practise these four answer shapes on GGSIPU BCA important questions before the BCA 205T end-term.
BCA 205T exam corner: 32 two-mark and 34 ten-mark practice questions by unit
| Unit | 2 marks | 10 marks | Solved examples |
|---|---|---|---|
| Unit 1 | 8 | 8 | 16 |
| Unit 2 | 8 | 9 | 7 |
| Unit 3 | 8 | 8 | 6 |
| Unit 4 | 8 | 9 | 7 |
BCA 205T exam questions and worked items in the notes, by unit
- Unit
- Unit 1
- 2 marks
- 8
- 10 marks
- 8
- Solved examples
- 16
- Unit
- Unit 2
- 2 marks
- 8
- 10 marks
- 9
- Solved examples
- 7
- Unit
- Unit 3
- 2 marks
- 8
- 10 marks
- 8
- Solved examples
- 6
- Unit
- Unit 4
- 2 marks
- 8
- 10 marks
- 9
- Solved examples
- 7
Four questions from the unit-end practice lists:
- Unit 1, 10 marks: Simplify F(A, B, C, D) = Σm(1, 3, 7, 11, 15) + d(0, 2, 5) using a K-map.
Pointer: d0 and d2 complete the quad A'B'; 3, 7, 11, 15 form CD; d5 stays unused. F = A'B' + CD (page 11). - Unit 2, 2 marks: How many flip-flops does a MOD-12 counter need?
Pointer: 4, since 23 = 8 < 12 ≤ 16. In a ripple design, 12 = 1100, so Q3 and Q2 feed the NAND. - Unit 3, 2 marks: Convert (A + B) × C into Reverse Polish Notation.
Pointer: operator after operands, no brackets. Answer: A B + C ×. - Unit 4, 2 marks: What is a page fault?
Pointer: the page's presence bit is 0, so the OS loads it from disk and restarts the instruction (page 69).
The BCA 205T notes list 32 two-mark and 34 ten-mark exam questions across 4 units, plus 36 solved examples and 20 quick numericals with answers.
More practice sits in the BCA 205T important questions.
BCA 205T and the BCA 205P COA lab (15 practicals), plus other GGSIPU BCA Sem 3 papers
Paired lab: BCA 205P COA lab notes. 15 practicals in the official list; 10 must be done.
The BCA 205P list is all digital logic, so only BCA 205T Units 1 and 2 feed it (our grouping):
- Unit 1 → practicals 1 to 10: gates, adders, subtractors, SOP and POS, MUX, DEMUX, decoder, encoder.
- Unit 2 → practicals 11 to 15: JK, D and T flip-flops, shift register, counter.
- Units 3 and 4 have no practical.
Other BCA Sem 3 papers: BCA 201T Python Programming, BCA 203T Dynamic Web Designing, BCA 207T Discrete Mathematics, the BCA 201P and 203P labs, BCA 261 Vocational Course, one elective and BCA 291T Human Values and Ethics.
Who writes and checks the BCA 205T COA notes?
- Prateek Talwar, author: Founder, Unnati Educations; Associate Company Secretary (ACS), ICSI, since 2019; B.Com, University of Delhi. Profile
- Ritik Rawat, subject reviewer: Senior Full Stack Developer, Unnati Educations; B.Tech. Profile
The reviewers who checked these BCA 205T K-map and counter answers also prepare GGSIPU important questions.
Do the BCA 205T notes cover the full GGSIPU syllabus?
Yes. Every official BCA 205T topic has its own section in the notes; no gap was found.
| Official unit | Official topics | Where in the notes | Status |
|---|---|---|---|
| Unit I | Boolean algebra laws, logic gates, K-maps SOP and POS, don't care condition; adder, subtractor, parallel binary adder/subtractor; multiplexers, de-multiplexers, decoders, encoders | Unit 1, pages 4 to 19 | Covered |
| Unit II | Latch, S-R, D, J-K, T, clocked flip-flop, race around condition, master slave flip-flop, realisation of one flip-flop using another; shift registers; ripple, synchronous and modulo counters | Unit 2, pages 23 to 35 | Covered |
| Unit III | Register transfer, bus and memory transfer, micro-operations; instruction codes, computer registers, instruction cycle, general register organization, stack organization, instruction formats, addressing modes | Unit 3, pages 39 to 52 | Covered |
| Unit IV | Peripheral devices, input-output interfaces, asynchronous data transfer, modes of transfer, priority interrupt, DMA; main, auxiliary, associative, cache and virtual memory | Unit 4, pages 56 to 70 | Covered |
BCA 205T official syllabus mapped to the notes
- Official unit
- Unit I
- Official topics
- Boolean algebra laws, logic gates, K-maps SOP and POS, don't care condition; adder, subtractor, parallel binary adder/subtractor; multiplexers, de-multiplexers, decoders, encoders
- Where in the notes
- Unit 1, pages 4 to 19
- Status
- Covered
- Official unit
- Unit II
- Official topics
- Latch, S-R, D, J-K, T, clocked flip-flop, race around condition, master slave flip-flop, realisation of one flip-flop using another; shift registers; ripple, synchronous and modulo counters
- Where in the notes
- Unit 2, pages 23 to 35
- Status
- Covered
- Official unit
- Unit III
- Official topics
- Register transfer, bus and memory transfer, micro-operations; instruction codes, computer registers, instruction cycle, general register organization, stack organization, instruction formats, addressing modes
- Where in the notes
- Unit 3, pages 39 to 52
- Status
- Covered
- Official unit
- Unit IV
- Official topics
- Peripheral devices, input-output interfaces, asynchronous data transfer, modes of transfer, priority interrupt, DMA; main, auxiliary, associative, cache and virtual memory
- Where in the notes
- Unit 4, pages 56 to 70
- Status
- Covered
Official sources: BCA Scheme of Examination, w.e.f. 2024-25 and BCA Scheme and Syllabus, 1st and 2nd Year, batch 2024-25 onwards.
Every course in GGSIPU notes is mapped to its official PDF the same way as this BCA 205T table.
BCA 205T COA notes FAQs
How do I get the full BCA 205T notes?
Tap "Get Full Notes" at the top of this page or the WhatsApp button at the end. The message is pre-filled with the BCA 205T code, so our desk knows which paper you need. The full 72-page notes covering all 4 units come only as a printed book, not as a PDF, ordered on WhatsApp.
What is the passing mark for BCA 205T?
BCA 205T is marked out of 100: 40 internal and 60 end-term. The BCA scheme and syllabus we checked do not print a pass percentage for this paper, so we do not quote one. Minimum end-term marks, grading and re-appear rules come from GGSIPU Ordinance 11, so check the current ordinance on ipu.ac.in before your exam.
Which BCA 205T unit has the most solved examples?
Unit 1 does, with 16 of the 36 solved examples in the BCA 205T notes. They cover Boolean law proofs, canonical SOP and POS, four K-map simplifications, a 4-bit parallel addition, a subtraction on the adder-subtractor, a function built on a 4:1 MUX and a full adder built from a 3-to-8 decoder. Units 2, 3 and 4 have 7, 6 and 7.
Is BCA 205T the same paper as BCA 205P?
No. BCA 205T is the 4-credit theory paper with a written end-term. BCA 205P is the separate 1-credit lab, where you build and verify gates, adders, multiplexers, flip-flops, a shift register and a counter. The BCA 205T notes explain those circuits in Units 1 and 2, but the lab has its own record, viva and marks.
Do the BCA 205T notes include memory and cache numericals?
Yes, in Unit 4. It works through a memory address map for 512 bytes of RAM and 512 bytes of ROM, disk access time at 6000 rpm, an associative memory match, cache average access time, a virtual address split and a FIFO page replacement string. Quick numericals add tag bits, latency and chip counts with answers.
Which textbooks do the BCA 205T notes follow?
The BCA 205T notes follow the books the official syllabus names: M. Morris Mano's Digital Logic and Computer Design (TB2) for Units 1 and 2, and his Computer System Architecture (TB1) for Units 3 and 4, with R.P. Jain (RB1) and Subrata Ghosal (RB3) as references. The basic computer and cache mapping examples use Mano's own setups.
Get the full BCA 205T Computer Organization and Architecture Notes on WhatsApp
| Unit | Pages | Solved examples | Exam questions |
|---|---|---|---|
| Unit 1 | 19 | 16 | 16 |
| Unit 2 | 16 | 7 | 17 |
| Unit 3 | 17 | 6 | 16 |
| Unit 4 | 18 | 7 | 17 |
Pages per unit in the full BCA 205T notes
- Unit
- Unit 1
- Pages
- 19
- Solved examples
- 16
- Exam questions
- 16
- Unit
- Unit 2
- Pages
- 16
- Solved examples
- 7
- Exam questions
- 17
- Unit
- Unit 3
- Pages
- 17
- Solved examples
- 6
- Exam questions
- 16
- Unit
- Unit 4
- Pages
- 18
- Solved examples
- 7
- Exam questions
- 17
Book only: these Computer Organization and Architecture notes in English come as a printed 72-page book, ordered on WhatsApp. They are not available as a PDF.
Unnati Educations is an independent education provider based in Vikaspuri, Delhi. We are not affiliated with, authorised by, or endorsed by Guru Gobind Singh Indraprastha University (GGSIPU). 'GGSIPU' and 'IPU' are used only to describe the syllabus our notes follow. For official information, visit ipu.ac.in.
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