Computer Science Previous Year Questions (page 4)

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A decision tree learns from labelled training data, so it is supervised learning. K-means is unsupervised, and reinforcement learning is a separate paradigm.

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B2C, C2B and C2C are all common e-commerce models, so none of them is the odd one out.

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Amazon sells products directly to individual consumers, making it B2C. Alibaba is mainly B2B, and Google is a search engine.

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Adobe Flash was used to create interactive multimedia (animation, audio, video), so it is an authoring tool. Word is a word processor and Photoshop is an image editor.

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Time sharing let many users at remote terminals use one computer interactively at the same time, which is seen as the start of computer communications.

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Pascal was designed by Niklaus Wirth to teach structured programming. It has block structure and control structures, so it is better suited to structured code than FORTRAN or BASIC.

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Browsers display web pages written in HTML (with CSS and JavaScript). None of the options is HTML: machine code, assembly language and C++ are not used to describe web pages.

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All three statements are true: a compiler takes the source program as input, translates the whole of it at once, and produces object code as output.

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Compaction moves the processes in memory so they sit next to each other, which gathers all free memory into one block and removes external fragmentation.

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In most languages, identifiers cannot begin with a digit, so 123Variable is invalid. myVariable and _myVariable are valid.

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This describes the physical organisation of memory: secondary storage keeps programs and data long-term, while main memory holds what is currently in use.

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Turbo C++ reports "Statement missing ;" and modern compilers say "expected ';'". None of the listed messages matches exactly.

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A graphics package is a set of libraries, such as graphics.h, that gives programs functions for drawing 2D graphics.

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In Turbo C++, Ctrl+F9 compiles and runs the program. Alt+F9 only compiles, and Alt+F5 shows the output screen.

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The control unit sends control signals (timing and control pulses) to the ALU, memory and I/O to direct how they work.

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User-defined header files in C++ use the .h extension, for example #include "myfile.h". .cpp is used for source files.

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Direct, indirect and immediate addressing are all commonly used by CPUs, so more than one option applies.

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Deleting a null pointer is a no-op that the C++ standard guarantees to be safe. The code compiles and runs normally.

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Buffer registers temporarily hold data so that fast and slow devices, which transfer data at different speeds, can work together.

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A PCI bus, connected through a bridge, extends the processor bus so that more devices can be attached.

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In memory-mapped I/O, I/O device registers are given addresses in the same address space as memory. The same load and store instructions then access both.

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In ADD X Y the operands are given by their memory addresses X and Y, which is absolute (direct) addressing.

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int array[10]; declares an array of 10 integers by giving the type, the name and the size in square brackets.

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A view is a virtual table, the stored result of a query. It does not hold its own data and is built from the base tables when used.

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A table can have only one primary key, although that key may be made of several columns (a composite key).

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Char arrays cannot be joined with +. s1 + " " tries to add two pointers, which is invalid, and an array cannot be initialised from such an expression, so the code gives a compile error.

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UNION is a set operator that combines the results of queries. PRIMARY KEY and NOT NULL are constraints.

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COUNT, SUM, AVG, MIN and MAX are aggregate functions. COMPUTE is not a standard SQL aggregate function.

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Charles Babbage designed the Difference Engine and the Analytical Engine, so he is called the father of the computer. Gosling created Java and Ritchie created C.

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ORDER BY sorts in ascending (ASC) order by default.

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Besides the condition flags (CF, ZF, SF, OF), the IA-32 EFLAGS register also provides TF (trap), IF (interrupt enable) and IOPL (I/O privilege level), so more than one option is correct.

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HAVING filters groups made by GROUP BY, while WHERE filters individual rows before they are grouped.

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In program-controlled I/O (polling), the CPU keeps checking a device's status flag until the device is ready.

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The WITH clause (a common table expression) defines a temporary named relation that exists only for that query.

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ROUND(65.726, −1) rounds to the nearest ten, because a negative position counts left of the decimal point, so 65.726 becomes 70.

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A matrix is sparse when most of its elements are zero, meaning more than half of the m × n elements.

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COMMIT makes the changes made by a transaction permanent. ROLLBACK undoes them, and TRUNCATE removes all rows from a table.

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Tables can be joined with join operations such as natural join and union join, or by using subqueries, so more than one option applies.

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Array elements are stored next to each other, so any element can be reached directly by its index in O(1) time. Arrays hold only one data type, and indexing starts at 0.

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Recursion uses a stack. Each call pushes an activation record, and the record is popped when the call returns.

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For a + (b*c) + (d*e): bc* is added to a to give abc*+, then de* is added to give abc*+de*+.

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Linear, circular and double-ended queues (deques) are all real types of queue, so none of the options is wrong.

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Before deleting, check for underflow (an empty queue). Overflow is checked before inserting.

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After the steps the deque is: 10; 20 10; 20 10 30; 10 30; 10 30 40; 10 30 40 10; 10 30 40; then 10 30 40 15.

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A deque (double-ended queue) allows insertion and deletion at both the front and the rear.

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With this convention, front and rear start at −1. Front = rear = −1 means the queue is empty, and front = rear ≥ 0 means it holds one element.

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Binary trees are traversed in preorder, inorder, postorder or level order. Randomized traversal is not a standard binary tree technique.

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A DBMS supports access by many users at once (concurrency control). Single-user-only access is not a DBMS feature.

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A doubly linked list allows traversal in both directions but needs extra space for the previous pointer. It is harder to implement than a singly linked list, not easier.