📌 Snapshot
- How a computer works, from CPU and memory to buses and operating system, with tables and practice MCQs.
- Why a computer needs RAM, ROM, cache and secondary storage, and how memory units convert with 1024.
- The three kinds of software, the three language translators and the five OS interfaces, side by side.
- Moore's law, microprocessor versus microcontroller, data types and data recovery, with the traps NTA sets.
📖 Detailed Notes
Written and reviewed by Rohit Singh, Computer Science & Commerce faculty at UniDrill (MCA, Osmania University · 6 years teaching). Based on NCERT Computer Science Class XI, Chapter 1.
What happens when you press the power button?
A phone that was completely "off" a moment ago is now running a whole operating system, with icons, a clock and a network connection. Where was that operating system while the power was off? Who woke it up? And why does the same phone carry both 8 GB of RAM and 128 GB of storage when both are "memory"?
The answer is one idea: every program takes the same road. It sleeps in permanent storage, is copied into fast working memory, and is then run by the processor one instruction at a time. The whole chapter hangs on that road.
The road in one line: secondary storage (permanent) → RAM (working memory) → cache (copies of what the CPU keeps asking for) → CPU registers → result written back to RAM → saved to secondary storage or sent to an output device.
The parts of a computer system
A computer is an electronic device that can be programmed to accept data (input), process it and give a result (output). A computer plus the extra hardware and software it needs is a computer system. Its parts are the CPU, memory, input devices, output devices and storage devices, working together as one unit. Computer systems come in every size, from a large server to a desktop, a laptop, a tablet or a smartphone.
The CPU (central processing unit) is the electronic circuit that does the actual processing, which is why it is called the brain of the computer. It is built on one or more chips called integrated circuits (ICs) made of semiconductor material. The CPU fetches a program and its data from memory, performs arithmetic and logic operations as the program instructs, and stores the result back in memory. It has three parts:
| Part | What it does | Remember it by |
|---|---|---|
| ALU (Arithmetic Logic Unit) | Performs all arithmetic operations (add, subtract) and logic operations (compare, AND, OR) | The calculator |
| CU (Control Unit) | Controls the order in which instructions execute, interprets them and directs the flow of data among memory, ALU and I/O devices | The traffic police |
| Registers | Tiny, very fast local memory inside the CPU chip that holds data, instructions or intermediate results during processing | The CPU's own scratch pad |
Input and output devices are the computer's senses and voice.
| Input devices | Output devices | |
|---|---|---|
| Job | Send control signals and data in, converting them to digital form | Take digital data out and convert it to a form humans understand |
| Examples | Keyboard, mouse, scanner, touch screen, braille keyboard, microphone (voice search) | Monitor, projector, speaker, headphone, printer, 3D printer, braille display |
| Special cases | A braille keyboard helps visually impaired users type | A braille display shows text output; a 3D printer builds a physical copy of a digital 3D design (used for prototypes and explored for medical use) |
Data typed through an input device first lands in the main memory (RAM). Only data you save goes on to secondary memory. Printers come in three common types: inkjet, laserjet and dot matrix.
From the abacus to wearables
The history of computing is a list of "what was the next problem?" answers. Learn it as a timeline, because NTA asks "who invented what" and "which came first".
| Year | Milestone | Why it mattered |
|---|---|---|
| About 500 BC | Abacus | The first calculating device; simple arithmetic only |
| 1642 | Pascaline (Blaise Pascal) | Mechanical calculator: addition and subtraction directly, multiplication and division by repeating them |
| 1834 | Analytical Engine (Charles Babbage) | Mechanical machine that could take input, process, store and give output; the basis of modern computers |
| 1890 | Tabulating machine (Herman Hollerith) | Summarised data stored on punched cards; a step towards programming |
| 1937 | Turing machine | The idea of a general purpose programmable machine that solves problems by running a stored program |
| 1945 | EDVAC and ENIAC (stored program concept, John von Neumann) | Computers that stored data and program together in memory |
| 1947 | Transistor (Bell Labs) | Replaced bulky vacuum tubes; made of semiconductor material |
| 1970 | Integrated circuit | A whole electronic circuit on a tiny silicon chip; computers shrank drastically |
| 1981 and 1984 | IBM PC (1981), Apple Macintosh (1984) | Computers for the home user |
| 1990s | World Wide Web | Pushed computers into everyday life |
A punched card is a stiff piece of paper that stores digital data as holes at fixed positions.
Von Neumann architecture has a CPU for arithmetic and logic, a memory that holds both data and programs, input and output devices, and communication channels. ENIAC is described as the first binary programmable computer based on this architecture. In the 1970s, Large Scale Integration (LSI) put a complete CPU on one chip, called a microprocessor. The 1980s brought Very Large Scale Integration (VLSI) with about 3 million components per chip, and today's chips are Super Large Scale Integration (SLSI).
Beyond the textbook. For the exam: ENIAC and EDVAC go with the stored program concept, and the integrated circuit is dated 1970. In reality: ENIAC (1945) was first programmed by setting switches and cables and worked in decimal, while the stored program idea was written up for EDVAC. The first integrated circuits were built in the late 1950s. The 1970 mark on the timeline is when large scale integration made a single chip CPU possible. Why it matters: when a question asks "which came first", use the order in the table above, and don't stretch it beyond what the question needs.
Moore's law. In 1965 Gordon Moore, an Intel co-founder, predicted that the number of transistors on a chip would double every two years while cost would halve. The number of transistors after $t$ years is
$$N = N_0 \times 2^{\,t/2}$$
Worked example: Moore's law. A chip has 1,000,000 transistors today. How many would the law predict after 10 years?
| Step | What we do | Result |
|---|---|---|
| 1 | Doublings in 10 years at one doubling per 2 years | $10 / 2 = 5$ |
| 2 | Each doubling multiplies by 2, so multiply by $2^5$ | $2^5 = 32$ |
| 3 | New count | $1{,}000{,}000 \times 32 = 32{,}000{,}000$ |
Common wrong step. Multiplying by $2 \times 10 = 20$ (doubling every year) or by $10 / 2 = 5$. Doubling is repeated multiplication, so the exponent counts the doublings.
After laptops came smartphones and tablets, thanks to smaller processors, faster memory and faster connections. The next wave is wearables (smart watches, lenses, headbands, headphones) and smart appliances in the Internet of Things (IoT), powered by artificial intelligence.
Memory: bits, bytes and the 1024 rule
A computer stores everything as bits, the binary digits 0 and 1. Bits are grouped into words. A nibble is 4 bits (for example 1001) and a byte is 8 bits, which is two nibbles (for example 01000110). Bigger units go up in steps of 1024, because $1024 = 2^{10}$.
| Unit | Value | Power of 2 |
|---|---|---|
| 1 KB (kilobyte) | 1024 bytes | $2^{10}$ bytes |
| 1 MB (megabyte) | 1024 KB | $2^{20}$ bytes |
| 1 GB (gigabyte) | 1024 MB | $2^{30}$ bytes |
| 1 TB (terabyte) | 1024 GB | $2^{40}$ bytes |
| 1 PB (petabyte) | 1024 TB | $2^{50}$ bytes |
| 1 EB (exabyte) | 1024 PB | $2^{60}$ bytes |
| 1 ZB (zettabyte) | 1024 EB | $2^{70}$ bytes |
| 1 YB (yottabyte) | 1024 ZB | $2^{80}$ bytes |
Worked example: how many bits in 2 KB?
| Step | What we do | Result |
|---|---|---|
| 1 | Convert KB to bytes with 1024 | $2 \times 1024 = 2048$ bytes |
| 2 | One byte is 8 bits | $2048 \times 8 = 16384$ bits |
Common wrong step. Using 1000 instead of 1024 gives 16000 bits. In computing the multiplier between units is always 1024.
Worked example: photos on a pen drive. A 2 GB pen drive stores photos of 5 MB each. How many whole photos fit?
| Step | What we do | Result |
|---|---|---|
| 1 | Convert GB to MB | $2 \times 1024 = 2048$ MB |
| 2 | Divide by the size of one photo | $2048 / 5 = 409.6$ |
| 3 | Only whole photos fit | 409 photos |
Worked example: word size and RAM. A 64-bit processor can address $2^{64}$ bytes. Express this in the largest unit.
| Step | What we do | Result |
|---|---|---|
| 1 | Split the power so that a unit appears | $2^{64} = 2^{4} \times 2^{60}$ |
| 2 | $2^{60}$ bytes is 1 EB | $2^{4} = 16$ |
| 3 | Result | 16 EB |
That is why a 64-bit word size makes RAM up to 16 exabytes feasible.
Beyond the textbook. For the exam: 1 KB = 1024 bytes and 1 GB = 1024 MB. In reality: standards bodies write the 1024 versions as KiB, MiB and GiB, and reserve KB, MB and GB for powers of 1000. Storage makers usually quote capacity in powers of 1000, which is why a 500 GB drive shows up as roughly 465 GB in an operating system that counts in 1024s. Why it matters: the gap isn't missing storage, it is two systems of counting.
Types of memory
Memory is of two kinds. Primary memory is the part the CPU talks to directly, so programs and data are loaded into it before processing. Secondary memory is for permanent storage.
| Feature | RAM | ROM | Cache | Secondary memory |
|---|---|---|---|---|
| What it is | Random Access Memory | Read Only Memory | High speed memory between CPU and RAM | Permanent storage such as HDD, SSD, CD/DVD, memory card, pen drive |
| Volatile? | Yes, wiped when power goes off | No, keeps contents | Yes (it holds copies) | No |
| Holds | Programs and data in use | Rarely changed content, such as the startup (boot loader) program | Copies of frequently used primary memory locations | Data, programs and results kept for the future |
| Speed | Fast, but slower than the CPU | Small but fast | Fastest of the three, nearest to the CPU | Slowest |
| Capacity and cost | Limited | Small | Smallest | Largest and cheapest per byte |
| CPU access | Direct | Direct | Checked first | Not direct: contents are first brought into RAM |
Why a cache exists. RAM is faster than a hard disk but still slower than the processor, so the CPU would keep waiting. A cache keeps copies of the data from frequently used RAM locations. The CPU looks in the cache first. If the data is there, it is read from the cache, and if not, RAM is accessed. This reduces the average access time.
The memory hierarchy from fastest and smallest to slowest and largest is registers, cache, primary memory (RAM and ROM), secondary memory. Speed, cost per byte and volatility all fall or rise along this ladder for a reason: fast memory is expensive, so there is little of it.
Secondary storage has changed too. An SSD (solid state drive) transfers data far faster than the older HDD, and small portable flash drives (pen drives) made moving data between computers simple.
Pause and predict: a computer has RAM but no secondary storage at all. Can you install software on it?
Check your answer: You can load a program into RAM and run it, but you cannot install it in any lasting sense. Installing means keeping the program for the future, and RAM is wiped when the power goes off. Permanent storage needs secondary memory.
Pause and predict: when you switch a computer on, who copies the operating system from the disk into RAM?
Check your answer: the small boot loader stored in ROM. ROM keeps its contents with the power off, so this tiny startup program is always there to bring the operating system into RAM.
Buses: how data travels inside
Data moves between components over physical wires called a bus. A bus is used between a USB port and a disk, a disk and main memory, and the CPU and main memory. Three buses together make the system bus.
| Bus | Carries | Direction | Why |
|---|---|---|---|
| Data bus | Data between components | Bidirectional | The CPU must both read from and write to memory |
| Address bus | The memory address the CPU wants to read or write | Unidirectional, CPU to memory | The CPU always tells memory where; memory never tells the CPU an address |
| Control bus | Control signals such as read or write | Unidirectional | Commands flow from the CPU to the other components |
Worked example: a memory read and a memory write. Trace what the CPU does.
| Step | Read from memory | Write to memory |
|---|---|---|
| 1 | CPU places the address of the location on the address bus | CPU places the address on the address bus |
| 2 | CPU sends a read signal on the control bus | CPU sends a write signal on the control bus |
| 3 | The memory controller places the data on the data bus | CPU places the data on the data bus |
| 4 | CPU receives the data from the data bus | The data is written at the address given |
The memory controller is dedicated hardware that manages the flow of data into and out of main memory. Because the CPU talks only to main memory, anything you type or any file you open from disk must first be placed in RAM.
Microprocessors and microcontrollers
A microprocessor is a CPU built on a single microchip, containing millions of components such as resistors, transistors and diodes. Nowadays almost every CPU is a microprocessor, so the two terms are used as synonyms.
| Generation | Era | Chip type | Word size | Maximum memory | Examples |
|---|---|---|---|---|---|
| First | 1971 to 1973 | LSI | 4 or 8 bit | 1 KB | Intel 8080 |
| Second | 1974 to 1978 | LSI | 8 bit | 1 MB | Motorola 6800, Intel 8085 |
| Third | 1979 to 1980 | VLSI | 16 bit | 16 MB | Intel 8086 |
| Fourth | 1981 to 1995 | VLSI | 32 bit | 4 GB | Intel 80386, Motorola 68030 |
| Fifth | 1995 to date | SLSI | 64 bit | 64 GB | Pentium, Celeron, Xeon |
Four specifications describe a microprocessor.
| Specification | Meaning | Unit or example |
|---|---|---|
| Word size | Maximum number of bits it can process at a time | Now 16 to 64 bits |
| Memory size | RAM it can use; depends on word size | 64 bit makes up to 16 EB feasible |
| Clock speed | Pulses generated per second by the internal clock; shows how fast instructions execute | Hz, kHz, now GHz (billions of pulses per second) |
| Cores | Basic computation units; more cores let it run several tasks at the same time | Dual core (2), quad core (4), octa core (8) |
A microcontroller is a small computing device with a CPU, a fixed amount of RAM and ROM, and other peripherals, all on one chip.
| Feature | Microprocessor | Microcontroller |
|---|---|---|
| On the chip | Only the CPU | CPU, RAM, ROM and peripherals |
| Purpose | General purpose computing | One specific task, embedded in a device |
| Size and cost | Larger, costlier system around it | Small and cheap, because it is built for one job |
| Examples | The CPU in a laptop | Washing machine, microwave, remote controller, digital camera, keyboard, mouse, pen drive |
In a fully automatic washing machine the microcontroller runs the whole cycle with no human help: fill with water, soak, wash, drain and spin dry. This is why smart home appliances use microcontrollers: they need a small, cheap, complete system for one task.
Data, information and the data life cycle
A computer treats everything as data: instructions, pictures, songs, videos and documents. Data are raw, unorganised facts. When they are processed they become meaningful information. Data, information and knowledge are not synonyms. Inside the machine everything is binary, but data enters in many forms, such as text, an image made of red, green and blue (RGB) pixels, or a video made of frames.
| Type | Structure | Examples |
|---|---|---|
| Structured | Strict record format in rows and columns; easy to sort | Attendance table, sales transactions, online railway ticket bookings, ATM transactions |
| Unstructured | No predefined record format | Audio and video files, graphics, text documents, social media posts, satellite images, a report card with text and logo |
| Semi-structured | No fixed structure, but internal tags or markings separate the elements | Email, HTML page, CSV file, a list of records where each value is preceded by a tag such as Name or Month |
Worked example: classify the data. A school stores Roll No, Name, Month and Attendance in a table. A parent receives a report card containing a logo, text and a signature. A file lists lines such as Name: Mohan Month: July Attendance: 98. Classify each.
| Data | Type | Reason |
|---|---|---|
| Table with fixed columns | Structured | Strict record format, sortable by any column |
| Report card with logo and text | Unstructured | Text and graphics with no fixed format |
| Lines with Name:, Month: tags | Semi-structured | No fixed record format, but every value carries a tag |
Data capturing, storage and retrieval. To process data you first capture it in digital form (keyboard, barcode reader, social media posts, satellite sensors). You then store it in a file or database for the future. Large organisations use data servers with big, fast storage, though setting one up is costly for small organisations. Finally you retrieve it when needed. As databases grow, minimising access time becomes more important.
Deletion and recovery. Writing zeros over every bit of a deleted file would take a long time. So when you delete data, the system only marks its address entry as free and shows the space as empty. The data is still there until something overwrites it. Data recovery is the process of retrieving deleted, corrupted or lost data from secondary storage, and it works only if the space has not been overwritten. This gives two security concerns.
| Concern | Risk | Protection |
|---|---|---|
| Unauthorised deletion | Someone or some software deletes your data | Limit access, use passwords for accounts and files, encrypt files |
| Unwanted recovery | Discarded disks reveal old data to a stranger | Delete or shred data with proper tools before disposing of the device |
Software: the three families
Hardware cannot work on its own. Software is the set of instructions and data that makes hardware work. You cannot touch it, and it acts as an interface between the user and the hardware. A document stored on disk is a soft copy and the printed version is a hard copy.
| Family | What it does | Examples |
|---|---|---|
| System software | Operates the computer by working directly with the hardware | Operating system, system utilities, device drivers |
| Programming tools | Help programmers write and translate programs | Languages, translators, editors, IDEs, debuggers |
| Application software | Works on top of system software for a user's needs | LibreOffice Calc, Adobe Photoshop, GIMP, a web browser, school management software |
A computer can work without application software, but it cannot work without system software.
System software has three parts. The operating system is the most basic system software; without it no other software can work. System utilities maintain and configure the system. Some ship with the OS (disk defragmentation, formatting, system restore) and some don't (antivirus, disk cleaner, disk compression). A device driver takes responsibility for one device at hardware level and acts as the interface between the device and the OS, hiding the hardware details. The OS can't handle every new device itself, so each device brings its own driver.
Programming languages. Low level languages depend on the machine. Machine language is 1s and 0s, directly executed but hard to write and debug. Assembly language uses English like words and symbols, but its code is computer specific: code for one type of CPU can't be used on another. High level languages (C++, Java, Python) are machine independent and written in English like sentences, but the computer cannot run them directly, so a translator is needed. Code you write is source code; its machine language form is object code.
| Translator | Converts | How it works | Needed again to run? |
|---|---|---|---|
| Assembler | Assembly language to machine language | Each assembler works for one processor's instruction set, so the machine code is not portable | After translation, no |
| Compiler | Whole high level source code to machine code | Reads the whole program, reports syntax errors, then produces object code | No: once translated, the compiler is not needed |
| Interpreter | High level source code, one line at a time | Translates a line, runs it, then moves to the next | Yes: always needed whenever the code is executed |
An IDE (Integrated Development Environment) combines a text editor, build tools and a debugger, so a program can be typed, compiled and debugged in one place. Python IDLE, Netbeans, Eclipse, Atom and Lazarus are examples. A debugger finds and corrects errors in source code.
Application software has two kinds. General purpose software is ready made for a wide audience (spreadsheet, photo editor, browser). Customised software is tailor made for one organisation or person, such as a school management system, accounting software or a website. Think of buying cloth off the shelf versus getting a garment stitched to your measurements.
| Type | Source code | Cost | Examples |
|---|---|---|---|
| FOSS (free and open source) | Freely available; anyone may improve it | Free | Ubuntu, Python, LibreOffice, OpenOffice, Mozilla Firefox |
| Freeware | Not available | Free to use | Skype, Adobe Reader |
| Proprietary | Not available; copyright held by the vendor | Must be purchased | Microsoft Windows, Tally, Quickheal |
The operating system
An operating system (OS) is a resource manager. It manages the CPU, RAM, disk, network and I/O devices, controls application software and device drivers, and handles security and user access. Windows, Linux, Android, Macintosh, Ubuntu and iOS are examples. It has two objectives. First, it provides services to build and run application programs: it loads a program into memory, gives it to the CPU, and decides the order when several programs wait. Second, it gives the user an interface.
| Interface | How you interact | Example systems |
|---|---|---|
| Command based | Type commands; mainly keyboard; less interactive; usually one program at a time | MS-DOS, Unix |
| Graphical (GUI) | Icons, menus and windows with mouse and keyboard | Microsoft Windows, Ubuntu, Fedora, Macintosh |
| Touch based | Touchscreen input read as commands (open an app, scroll) | Android, iOS, Windows 8.1 and 10 on touch devices |
| Voice based | Spoken commands, useful for users who cannot use mouse, keyboard or touch | Siri (iOS), Google Now (Android), Cortana (Windows 10) |
| Gesture based | Waving, tilting, eye motion, shaking; still evolving, with promise in gaming and medicine | Some Android and iOS phones and laptops |
The OS performs four management jobs.
| Function | Resource | What it does |
|---|---|---|
| Process management | CPU | A process is a task in execution. The OS shares the CPU among processes, allocates resources and lets processes exchange information so that tasks finish in minimum time |
| Memory management | Main memory | Allocates and frees memory to running processes on the go, keeps track of each location as free or occupied, and takes memory back when a process ends |
| File management | Secondary memory | Creation, updation, deletion and protection of files; stops one user from opening another user's unshared files |
| Device management | I/O devices | Works with device drivers, offers configuration options and limits device access to authorised users and software |
Remember the pairing: memory management looks after main memory and file management looks after secondary memory.
Exam traps
| The trap | Why it's tempting | The truth |
|---|---|---|
| "RAM is non-volatile." | It stores your work | RAM is volatile; ROM and secondary memory are not |
| "Cache is slower than RAM." | Cache sounds like storage | Cache is faster than RAM and sits between CPU and RAM |
| "1 KB = 1000 bytes." | Kilo means 1000 in SI | In this chapter, 1 KB = 1024 bytes and each larger unit is 1024 times the previous |
| "The address bus is bidirectional." | Data goes both ways | Only the data bus is bidirectional; address and control buses are unidirectional |
| "A compiler is needed every time the program runs." | Confused with the interpreter | After translation the compiler is not needed; an interpreter is always needed |
| "Antivirus is application software." | It is a program users install | It is a system utility, which belongs to system software |
| "A microcontroller has only a CPU." | The name sounds like microprocessor | A microcontroller has CPU, RAM, ROM and peripherals on one chip |
| "Freeware and FOSS are the same." | Both cost nothing | FOSS gives the source code; freeware doesn't |
60-second revision
| Topic | Lock this in |
|---|---|
| CPU | ALU (arithmetic and logic) + CU (control) + registers |
| Data flow | Input → RAM → CPU → RAM → output or storage |
| Memory units | Nibble 4 bits; byte 8 bits; every step above is 1024 |
| RAM / ROM | RAM volatile, working memory; ROM non-volatile, holds boot loader |
| Hierarchy | Registers → cache → RAM/ROM → secondary |
| Buses | Data (two way), address (one way, CPU to memory), control (one way) |
| Moore's law | 1965, transistors double every two years, cost halves |
| Microcontroller | CPU + RAM + ROM + peripherals on one chip, one task |
| Data types | Structured (table), semi-structured (tags), unstructured (free form) |
| Deletion | Address marked free; recoverable until overwritten; shred before disposal |
| Software | System, programming tools, application |
| Translators | Assembler (assembly), compiler (whole, once), interpreter (line by line, always) |
| OS functions | Process, memory, file, device management |
Memory arithmetic sheet
| Quantity | Formula | When to use |
|---|---|---|
| Bytes from bits | $\text{bytes} = \text{bits} / 8$ | Converting size of data |
| Next unit up | $1\ \text{unit} = 1024$ of the one below | KB to MB to GB and so on |
| Values from $n$ bits | $2^{n}$ | Counting codes, addresses or memory locations |
| Moore's law | $N = N_0 \times 2^{\,t/2}$ | Predicting transistor count after $t$ years |
Where this chapter connects
- Next: Encoding Schemes and Number System explains the binary, octal and hexadecimal in which every item in this chapter is stored.
- Later in the unit: Emerging Trends builds on microcontrollers (IoT) and storage (cloud) from here.
- Programming link: Getting Started with Python uses the interpreter idea from the translators table.
- Class XII link: Computer Networks takes the idea of data moving between components to data moving between computers.
🎯 Practice MCQs
First 3 questions free · create a free account to unlock the rest — answers & explanations included, no payment needed
Q1. Which part of the CPU controls the sequence of instruction execution and directs the flow of data among memory, ALU and input or output devices?
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Answer: B
The Control Unit controls the order of instruction execution, interprets instructions and guides data flow. The ALU performs arithmetic and logic operations, registers hold data inside the CPU, and cache is a high speed memory between the CPU and main memory.
Q2. Consider the statements. (1) RAM retains its data when the power is switched off. (2) ROM stores the startup program that loads the operating system. (3) Cache memory lies between the CPU and primary memory. Which are correct?
▸ Show answer & explanation
Answer: B
Statement 1 is wrong because RAM is volatile and loses its contents without power. Statements 2 and 3 are correct, so the answer is 2 and 3 only.
Q3. Match List I with List II. List I: (i) Assembler (ii) Compiler (iii) Interpreter. List II: (p) translates one line at a time and is always needed to run the program (q) converts assembly language to machine language (r) translates the whole source code at once and is not needed after translation
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Answer: A
The assembler handles assembly language, the compiler translates the whole program once, and the interpreter works line by line. Options B, C and D each swap at least two of these pairs.
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Q4. A school stores monthly attendance in a table with the columns Roll No, Name, Month and Attendance percentage. This is an example of
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Answer: C
Data arranged in a fixed row and column format that can be sorted is structured. Unstructured data has no predefined format, and semi-structured data uses tags instead of a fixed record layout. Processed meaningful results are information, but the table itself is stored data.
Q5. Assertion (A): A computer can run without any application software but cannot run without system software. Reason (R): System software works directly with the hardware, while application software works on top of system software.
▸ Show answer & explanation
Answer: A
Without an operating system there is nothing to run programs on, but a machine with no word processor still works. R gives exactly that reason, so it explains A.
Q6. Which of the following is NOT a function of an operating system?
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Answer: D
Translating source code is the job of a language translator such as a compiler, which belongs to programming tools. Options A, B and C are memory, file and device management respectively.
Q7. Arrange the memories in decreasing order of speed.
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Answer: B
Registers sit inside the CPU and are fastest, then cache, then RAM, and secondary storage is slowest. Options A, C and D place cache or RAM in the wrong position.
Q8. Which statement about the system bus is correct?
▸ Show answer & explanation
Answer: C
The control bus is unidirectional and carries control signals. The data bus is bidirectional and carries data, the address bus is unidirectional and carries addresses, and the system bus is the combination of all three buses, not one wire.
Q9. How many bits are there in a file of 4 KB?
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Answer: D
4 KB is 4 times 1024 bytes, which is 4096 bytes, and each byte has 8 bits, giving 32768 bits. Option B forgets to convert bytes to bits, and options A and C use 1000 instead of 1024.
Q10. A chip has 2 million transistors. If transistor count doubles every two years, how many transistors would you expect after 6 years?
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Answer: C
In 6 years there are 3 doublings, so the count is multiplied by 2 to the power 3, which is 8. That gives 2 times 8, which is 16 million. The value 12 million adds instead of multiplying, and 4 million or 8 million count too few doublings.
Q11. The control unit of a fully automatic washing machine runs the wash cycle without human help. This is possible because the machine contains
▸ Show answer & explanation
Answer: B
Devices built for one specific task embed a microcontroller, which is a complete small system on one chip. A general purpose microprocessor is overkill, and a data server is meant for storing large amounts of data.
Q12. Which of the following is an example of Free and Open Source Software?
▸ Show answer & explanation
Answer: C
Ubuntu has freely available source code that anyone can improve. Microsoft Windows and Tally are proprietary software, and Skype is freeware, which is free to use but has no available source code.
Q13. When a file is deleted from a hard disk in the normal way, what happens?
▸ Show answer & explanation
Answer: B
Overwriting every bit would be slow, so the system only marks the space as free. The data remains until other data overwrites it. That is why recovery is possible and why old disks should be shredded before disposal.
Q14. Which interface allows a user to give input by waving a hand, tilting the device or moving the eyes?
▸ Show answer & explanation
Answer: D
Gestures such as waving, tilting, shaking and eye motion belong to the gesture based interface. Command based input is typed text, a GUI uses icons and menus with a mouse, and touch uses the screen.
Q15. A 64-bit word size makes it feasible to use RAM of up to
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Answer: B
A 64-bit address can name 2 to the power 64 bytes, which is 2 to the power 4 times 2 to the power 60, that is 16 EB. Option A confuses the bit count with a size, and options C and D are not what 2 to the power 64 bytes works out to.
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