DSSSB TGT Computer Science Practice Set 3

Explanation

A CD-ROM stores data along one continuous spiral track running from the centre outward. Hard disks and floppy disks use concentric circular tracks, and RAM is semiconductor memory with no tracks.

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The OS keeps a Process Control Block (PCB) for each process. It holds the process state, program counter, registers, scheduling information and memory details.

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RISC (Reduced Instruction Set Computer) keeps only a small set of simple, essential instructions on the chip, so each instruction runs fast, often in one clock cycle. CISC uses many complex instructions.

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Bandwidth = 10 × 3000 Hz + 9 guard bands × 300 Hz = 30,000 + 2,700 = 32,700 Hz. Ten channels only need 9 guard bands between them.

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Classic ASP uses VBScript as its default scripting language. JScript can be chosen with a page directive.

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Bits per frame = 800 × 600 × 8 = 3,840,000. At 40 frames/s this is 3,840,000 × 40 = 153,600,000 bits/s = 153.6 Mbps.

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Quick sort and merge sort are divide-and-conquer algorithms and are normally written recursively. Bubble sort and insertion sort are simple iterative algorithms.

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In a star topology every device has its own point-to-point link to a central hub or controller. In a mesh, every device links directly to every other device.

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IEEE 754 uses 32 bits for single precision, 64 bits for double precision and 80 bits for the x87 extended-precision format.

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Corrected: the book's key says (c). The additional information is carried by the exception object that is thrown.

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Tree A is strictly binary because every node has 0 or 2 children. Tree B is not, because L and R each have only one child. Tree C is a full tree of height 2 with every level filled, so it is complete.

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DMA (Direct Memory Access) lets a peripheral transfer data directly to or from main memory without the CPU handling each word. The CPU only starts the transfer and is told when it ends.

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Rows 1 to i−1 hold 1 + 2 + … + (i−1) = i(i−1)/2 elements. A[i, j] is the j-th element of row i, so its location is i(i−1)/2 + j. Check: A[1,1] gives 0 + 1 = 1.

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In C++ an else pairs with the nearest preceding unmatched if (the dangling-else rule), whatever the indentation. So the else belongs to if#2.

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The OSI model has 7 layers: Physical, Data Link, Network, Transport, Session, Presentation and Application.

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Bit synchronization is done by the Physical layer, not the Data Link layer. Data Link handles framing, error control and flow control. The other pairs are correct.

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Each character needs 1 start + 7 data + 1 parity + 1 stop = 10 bits. So 19,200 bps ÷ 10 = 1920 characters per second.

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SSL encrypts data and is traditionally placed at the Presentation layer in OSI terms, because encryption and decryption are presentation-layer jobs. It sits between the application and transport layers.

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In Java, String is a class (a reference type), not a primitive type. boolean, byte and double are primitives.

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new String[3] creates an array of references, and each element starts with the default value null. So printing var1[1] prints null.

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An EJB (EJB 2.x) bean class comes with two interfaces, the home interface and the remote (or component) interface, plus one XML deployment descriptor (ejb-jar.xml).

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Only 90% of the code was tested, and the success probability is 0.9. So reliability is at most 0.9 × 0.9 = 0.81.

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The parentheses bind * to p first, so p is a pointer, and that pointer points to an array of 5 ints. Without parentheses, int *p[5] would be an array of 5 pointers to int.

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Since 1~2 and 2~3, all of 1, 2 and 3 fall into one equivalence class. That needs all 3 × 3 = 9 ordered pairs. R already has 2, so 9 − 2 = 7 pairs must be added.

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x²/(1+x²) is 0 at x = 0 and approaches 1 as x grows, but never reaches 1 because x² < 1 + x². So the range is [0, 1).

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Answer as per the book's key (c) 2¹⁶ (the original exam key).

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In ETL, the staging area is the intermediate storage where extracted data is cleaned and transformed before it is loaded into the data warehouse.

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Seek time is the time to move the read/write head to the correct track. Rotational latency is the wait for the sector to rotate under the head, and access time is the two combined.

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A 4-bit parallel (ripple-carry) adder uses one half adder for the least significant bit, which has no carry-in, and three full adders for the other three bits.

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10Base5 is the original Thick Ethernet (thicknet): 10 Mbps, baseband, 500 m segments on thick coaxial cable. 10Base2 is Thin Ethernet.

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Cache memory is a small, very fast memory between the CPU and main memory. It holds frequently used data and instructions, so programs run faster.

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Nulls do not reduce storage space, so (D) is false. The other statements are true: heavy normalization means more joins, foreign keys enforce referential integrity, and a primary key uniquely identifies a row.

Explanation

The accumulator holds an operand and stores the result of arithmetic and logic operations. The program counter holds the next instruction's address, and the stack pointer holds the top of the stack.

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A 14-unit job with a 2-unit quantum runs in 7 slices. A switch is counted between slices, giving 7 − 1 = 6 context switches.

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Aging gradually raises the priority of processes that have waited a long time. This prevents starvation (indefinite blocking) of low-priority jobs.

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IN matches any value in the list, so the query returns customer_name and telephone of customers whose city is Jaipur, Delhi or Agra. A customer cannot live in all three cities at once.

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ROM keeps its contents when power is off, so it is non-volatile. RAM and cache lose their data when power is removed.

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By De Morgan's law, (A·B)' = A' + B'.

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list() on a string makes a list of its individual characters, so list('PEACE') gives ['P', 'E', 'A', 'C', 'E'].

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range(6, 1, −2) gives 6, 4 and 2, so the loop runs 3 times. print(end='*$$') prints only '*$$' with no newline, giving *$$*$$*$$.

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Python's membership operators are 'in' and 'not in'. 'is' is an identity operator, and 'or'/'not' are logical operators.

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str.partition(sep) always returns a 3-tuple: the part before the separator, the separator, and the part after it. split() can return any number of parts.

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Optical fibre carries light signals. This gives very high bandwidth and long distances, and it is immune to electromagnetic interference, but it is expensive.

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ARPANET stands for Advanced Research Projects Agency Network. It was the US Department of Defense network that led to the Internet.

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UNIX inodes use an extended indexed scheme: 12 direct block pointers plus single, double and triple indirect blocks. This lets very large files be addressed.

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In Flash, a fade effect is made with a motion tween that changes the symbol's alpha (transparency) from 100% to 0%, so the symbol gradually disappears.

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3NF removes transitive dependencies, where a non-key attribute depends on another non-key attribute. 2NF removes partial dependencies.

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Digital drawing is a graphics application. Payroll, HR management and invoicing all store and manage records in databases.

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With public inheritance, protected members stay protected and public members stay public in the derived class. So Name is protected and Readdata() is public. The private AadharNo is not accessible in Student.

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ifstream opens a file for input (reading). ofstream is for writing. ios::read is not a valid mode.

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Visual Basic variable names cannot contain spaces, so "First Name" is invalid. The keyed answer treats the other names as valid.

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VB's default (binary) string comparison uses character codes. 'C' (67) is less than 'c' (99), so "Care" < "care" is true.

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A stack machine takes its operands implicitly from the top of the stack. So instructions like ADD need no address fields, which makes them zero-address instructions.

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With FIFO and 3 frames: 7, 0, 1, 2 are faults (4 so far), 0 is a hit, then 3, 0, 4, 2, 3 are all faults. That gives 9 page faults.

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CSS describes how HTML elements are displayed (presented), not how they are stored within tags. So (C) is false.

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XML separates data from HTML, so it does not separate design (presentation) from HTML. The other options are standard XML features.

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A foreign key is an attribute in one table that refers to the primary key of another table, linking the two tables.

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DROP TABLE EMPLOYEE removes the table's structure and all its data. DELETE FROM only removes rows and keeps the structure.

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In a VB Select Case statement, multiple values in one Case are separated by commas, for example Case 1, 3, 5.

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Keywords (reserved words) such as If, Dim and Loop have a predefined meaning in Visual Basic, so they cannot be used as variable names.

Explanation

With a quantum of 4: P1 runs 0–4, P2 runs 4–7, P3 runs 7–10, then P1 runs 10–30. Waiting times are P1 = 6, P2 = 4, P3 = 7. The average is 17/3 ≈ 5.66 units.

Explanation

The full sequence starts with designing the solution, then writing code, compiling it to object code, linking libraries, loading into memory and executing. The other options leave out design or linking.

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Encapsulation wraps data (characteristics) and the functions that act on it (behaviour) into one unit, the class. Data hiding and abstraction are results of this.

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An embedded system is electronics and software built into a product for a dedicated function, such as a washing machine or microwave controller, rather than a general-purpose computer.

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Bandwidth is the transmission capacity of a channel, meaning how much data it can carry per unit time, measured in bps or Hz.

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An internal computer bus moves data in parallel over very short distances, so it gives a far higher data rate than telephone lines, modems or leased lines.

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An XML parser reads an XML document and turns it into an XML DOM object (a tree) that programs such as JavaScript can access and change.

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Capacity = tracks per side × sides × sectors per track × bytes per sector. So sectors per track = 21,504,000 ÷ (600 × 2 × 512) = 21,504,000 ÷ 614,400 = 35.

Explanation

Answer as per the book's key (b).

Explanation

In a Schmitt trigger inverter, the output goes HIGH to LOW when a rising input crosses the upper trip point, 2.8 V. It goes LOW to HIGH when a falling input crosses the lower trip point, 1.8 V.

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The upper four OSI layers (Transport, Session, Presentation, Application) are host-to-host (end-to-end) layers. The lower layers handle hop-by-hop delivery over the network.

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A binary storage cell with input, output and Read/Write control lines is the basic building block of a memory. Each cell stores one bit, which is read or written as the control lines select.

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JavaScript variables can be declared with var, and JavaScript is untyped (dynamically typed), so the same variable can hold any type. Both statements are true.

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A run-time error raises an exception, an abnormal condition while the program runs. Syntax errors are caught at compile time.

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The server runs the ASP.NET code and sends only the resulting HTML to the browser. So the page received contains no ASP.NET code.

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Memory allocated with new[] must be freed with delete[]. So delete [] pp; is correct, and plain delete pp; on an array is undefined behaviour.

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Deadlock is impossible if R ≥ n(k−1) + 1, where n is the number of processes and k the units each needs. Here 3 × (2−1) + 1 = 4. With 4 units, at least one process can always finish.

Explanation

4096 = 2¹², which is 1 followed by twelve 0s in binary. That takes 13 bits, while 12 bits only go up to 4095.

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Java garbage collection automatically reclaims the memory of objects that no longer have any references to them, so the programmer does not free memory by hand.

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DTD stands for Document Type Definition. It defines the legal elements, attributes and structure of an XML or XHTML document.

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GIF is a compressed, widely supported image format made for the web. BMP and TIFF files are large and not suited to web pages, and HTML is not a graphics format.

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In classic ASP (VBScript), variables are declared with the Dim statement, for example Dim name.

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GIF is a compressed, widely supported image format made for the web. BMP and TIFF files are large and not suited to web pages, and HTML is not a graphics format.

Explanation

In classic ASP (VBScript), variables are declared with the Dim statement, for example Dim name.

Explanation

Corrected: the book's key says (b). HAVING can be used without GROUP BY (the whole result is one group), and WHERE is applied before HAVING, so both statements are false.

Explanation

In a synchronous parallel-load shift register, all 8 bits enter their flip-flops at the same time. So a single clock pulse loads the whole byte.

Explanation

AB → C holds because every (A, B) pair is unique, and B → C holds because b1→c1, b2→c2 (twice) and b3→c4. B → D fails (b2 gives d2 and d3), as do D → A and A → D.

Explanation

Frequencies from about 1 GHz to 300 GHz are microwaves, used for satellite, radar and point-to-point links. Radio waves are below this range and infrared is above it.

Explanation

Depreciation spreads (allocates) the cost of a fixed asset over its useful life, matching the expense to the periods that benefit from the asset.

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Net profit earned is added to the owner's capital. Drawings reduce capital, while paying creditors or buying furniture only changes assets and liabilities.

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In a matriarchy the eldest woman heads the family, and property and lineage pass from mother to daughter. The Khasi and Garo of Meghalaya are examples.

Explanation

Per the keyed answer, designing co-curricular activities is treated as a separate activity, not one of the core aspects of curriculum. The core aspects are goals and objectives, design (content and methods) and results (evaluation).

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Curriculum is seen as a means to achieve educational goals, not an end in itself. It includes all activities and serves as both a resource and an experience.

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Curriculum is the sum total of all experiences and activities, academic and co-curricular, that a school provides to shape a student. Syllabus covers only the subject content.

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Vygotsky's socio-cultural theory centres on social interaction, culture and language (with ZPD and scaffolding). Assessment is not one of its key concepts.

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Lev Vygotsky gave the concepts of the Zone of Proximal Development and scaffolding, meaning support from a more knowledgeable person that is gradually withdrawn.

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The Right of Children to Free and Compulsory Education Act, 2009 guarantees free and compulsory education to children aged 6 to 14 in a neighbourhood school.

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Curriculum is shaped by learners' needs and abilities and by social aspects. Gender roles should not determine curriculum, which must be gender-neutral.

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The Education Commission of 1964–66 was chaired by Dr. D. S. Kothari, so it is popularly called the Kothari Commission.

Explanation

Seeing all women as weak and needing protection is a stereotype: a fixed, oversimplified belief applied to a whole group.