Key takeaways
- Cache address splitting, AMAT, pipeline speedup and IEEE 754 are the main numericals.
- Learn the addressing modes with one example and the effective address for each.
- Each section has exam tips and formula boxes, and the last page lists the most asked practice questions.
- These are original Uncodemy revision notes, not official university notes; check your own syllabus.
About these COA handwritten notes
This page offers Uncodemy's Computer Organization and Architecture notes as a free handwritten-style PDF. Computer Organization and Architecture explains how a CPU, memory and I/O work together: instructions, control, arithmetic, caches and pipelines. The notes are written in short points with neat tables, labelled diagrams, boxed formulas and exam tips, so you can revise a full unit in one sitting instead of reading a long textbook chapter.
Please note: these are original Uncodemy revision notes. They follow the common syllabus that most Indian universities share for this subject, but they are not official university notes. Check your own university syllabus and add anything it lists that is missing here.
What's inside the COA notes
The PDF is arranged in 8 sections plus a final page of most asked practice questions. The sections follow the usual unit order of a Computer Organization and Architecture syllabus, so you can map them to your own units quickly. Here is what each section covers.
Basic structure of a computer
Functional units, Von Neumann vs Harvard architecture, important registers (PC, IR, MAR, MDR) and bus organisation.
Instruction set and addressing modes
Instruction formats, all common addressing modes with effective address calculation, and RISC vs CISC.
Control unit
The instruction cycle with micro-operations, and hardwired vs microprogrammed control units.
Computer arithmetic
Signed number representation, Booth's multiplication algorithm, division and IEEE 754 single and double precision.
Memory hierarchy
Cache basics, direct, associative and set-associative mapping with a solved direct-mapped example, and replacement and write policies.
Pipelining
Pipeline stages, speedup and throughput formulas, and structural, data and control hazards with forwarding.
I/O organisation
Programmed I/O, interrupt-driven I/O and DMA, plus interrupts and their priority.
Performance measures
CPI, MIPS, execution time and Amdahl's law with worked formulas.
Most asked questions (practice)
Ten exam-style questions, from the instruction cycle to Amdahl's law.
How to use handwritten notes to revise COA
COA rewards students who can split addresses and apply formulas without mistakes, so revise with a calculator and the formula boxes in the notes.
- Make a single formula sheet for AMAT, pipeline speedup, CPI and Amdahl's law.
- Split addresses into tag, index and offset for direct, associative and set-associative caches on the same example.
- Practise one Booth's multiplication and one IEEE 754 conversion every day of the last week.
- Draw the instruction cycle and DMA block diagrams until you can label every signal.
A simple three-pass method works well with handwritten notes. In the first pass, read one section and underline only what you do not already know. In the second pass, close the notes and write the definitions, diagrams and steps for that section on a blank sheet, then compare and correct in a different colour. In the third pass, a day or two later, answer two or three exam-style COA questions in timed conditions using only memory. Add your own examples and doubts in the margins so the PDF becomes your personal revision copy.
Formulas, diagrams and definitions to memorise
- Address split for a direct-mapped cache: tag, line (index) and block offset bits.
- AMAT = hit time + miss rate x miss penalty, and its two-level form.
- Pipeline speedup for n instructions on k stages: n k / (k + n - 1), ideally close to k.
- IEEE 754 single precision layout: 1 sign bit, 8 exponent bits with bias 127, 23 mantissa bits.
- Amdahl's law: speedup = 1 / ((1 - f) + f / s), and the Booth's algorithm recoding table.
Common mistakes that cost marks
- Forgetting the bias when writing the IEEE 754 exponent.
- Using byte addresses and word addresses together in cache questions without converting.
- Ignoring stalls when the question gives hazards in a pipeline problem.
- Missing the arithmetic right shift step in Booth's algorithm.
Exam focus: COA topics that carry the most marks
COA papers carry a lot of numericals. These topics come up most often.
- Cache mapping and AMAT.
- Pipeline speedup, hazards and stalls.
- Booth's algorithm and IEEE 754 representation.
- Addressing modes, control unit design and DMA.
Typical long questions
- Explain the instruction cycle with micro-operations.
- List the addressing modes with examples and effective address calculation.
- Compare hardwired and microprogrammed control.
- Multiply two signed numbers using Booth's algorithm.
- Represent a decimal number in IEEE 754 single precision.
- Find tag, set and offset bits for a given cache organisation.
- Find the speedup of a k-stage pipeline and explain hazards.
Marks per question change between universities and years, so confirm the pattern on a recent official paper. In long answers, start with a definition, add a labelled diagram or table, explain the steps and finish with an example or comparison. Underline the key term in each answer and leave a line between steps, because examiners mark faster when the structure is easy to see.
A 7-day revision plan for COA
- Day 1: Basic structure of a computer, Instruction set and addressing modes.
- Day 2: Control unit, Computer arithmetic.
- Day 3: Memory hierarchy, Pipelining.
- Day 4: I/O organisation.
- Day 5: Performance measures.
- Day 6: redo the numericals: Booth's algorithm, IEEE 754, cache address splitting, AMAT and pipeline speedup.
- Day 7: answer the most asked practice questions at the end of the notes from memory, then solve one official previous year paper in three hours and mark the units that cost you time.
Keep a single sheet of formulas, definitions and diagrams from the notes for the last hour before the exam, and do not start new topics on the final day.
Who these notes are for
- B.Tech CSE, IT and ECE students preparing for the semester COA exam.
- BCA and MCA students with a computer organisation or architecture paper.
- GATE CS aspirants revising the COA numericals.
- Students who want to understand how hardware affects program performance.
The notes are a revision aid, not a first textbook. If a COA topic is new to you, learn it from your prescribed book or class lectures first, then come back to the notes to compress and revise it. For practice, pair them with the Computer Organization and Architecture Important Questions PDF page and your university's official previous year papers. If your syllabus has a topic that is not covered here, you can ask for it through the handwritten notes request page linked below.
Download Computer Organization and Architecture Handwritten Notes PDF
COA Handwritten Notes PDF (Free Download)
The PDF carries the same content as this page in a clean, print-ready layout, so you can read it offline and keep it for revision.
7 pages · 290 KB · PDF · Updated 5 Nov 2026