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WBBSE Madhyamik Computer Application (Optional) study materials
WBBSE Madhyamik Computer Application (Optional) study resources

WBBSE Madhyamik Computer Application (Optional) practice questions

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Question 1Computer fundamentals and number systems

In the decimal number system, what does the base 10 signify about the digits used?

  1. Digits are written using exactly ten bits per position
  2. Ten distinct digit symbols 0 to 9 are used and each place value is a power of ten Correct answer.
  3. Only the digits 0 and 1 are available for building numbers
  4. Each position increases in value by a factor of two

Explanation

The base of a positional number system tells how many distinct digit symbols exist and the factor by which each place value grows. In base 10 there are ten symbols (0 through 9) and each position is ten times the one to its right.

Question 2Computer fundamentals and number systems

Which of these is a valid binary number?

  1. 12A0
  2. 1021
  3. 9081
  4. 1101 Correct answer.

Explanation

A binary number may contain only the symbols 0 and 1. The string 1101 uses only these two symbols, so it is a legitimate base-2 numeral.

Question 3Computer fundamentals and number systems

The decimal value of the binary number 1011 is:

  1. 11 Correct answer.
  2. 9
  3. 13
  4. 15

Explanation

Place values in binary are 8, 4, 2, 1 from left to right. Summing where a 1 appears gives 8 + 2 + 1 = 11, so 1011 in binary equals eleven in decimal.

Question 4Computer fundamentals and number systems

How many bits are present in one byte?

  1. 32
  2. 8 Correct answer.
  3. 16
  4. 4

Explanation

A byte is defined as a group of eight bits, and it is the standard unit of storage addressing. Each bit holds one binary digit, so a byte stores eight binary digits.

Question 5Computer fundamentals and number systems

Which storage unit is the largest among the following?

  1. 1 kilobyte
  2. 1 megabyte
  3. 1 gigabyte
  4. 1 terabyte Correct answer.

Explanation

The metric-style prefixes used for storage grow by a factor of about one thousand each step: kilobyte, then megabyte, then gigabyte, then terabyte. A terabyte therefore represents the largest quantity in this list.

Question 6Computer fundamentals and number systems

Which component of a computer is described as the 'brain' that fetches and executes instructions?

  1. Random Access Memory
  2. Power supply unit
  3. Hard disk drive
  4. Central Processing Unit Correct answer.

Explanation

The Central Processing Unit fetches instructions from memory, decodes them, and carries out the arithmetic and logic operations. It coordinates the rest of the machine, which is why it is informally called the brain of the computer.

Question 7Computer fundamentals and number systems

Which of the following is an example of system software?

  1. An operating system Correct answer.
  2. A spreadsheet application
  3. A photo editor
  4. A web browser

Explanation

System software manages hardware and provides a platform on which other programs run; the operating system is the main example. Application software, by contrast, is written to perform user-facing tasks.

Question 8Computer fundamentals and number systems

What does the abbreviation ROM stand for in computer terminology?

  1. Read Only Memory Correct answer.
  2. Random Operating Memory
  3. Rapid Output Module
  4. Run Once Memory

Explanation

ROM stands for Read Only Memory, a type of memory whose stored contents are normally not changed by ordinary programs. It is used to hold firmware such as the startup instructions of a computer.

Question 9Computer fundamentals and number systems

The hexadecimal number 1A equals which decimal value?

  1. 20
  2. 16
  3. 26 Correct answer.
  4. 28

Explanation

In hexadecimal the digit A stands for ten. The place values are 16 and 1, so 1A equals 1×16 + 10×1 = 26 in decimal.

Question 10Computer fundamentals and number systems

The decimal number 45 converted to binary is:

  1. 100101
  2. 101011
  3. 101101 Correct answer.
  4. 110101

Explanation

Repeated division by 2 gives remainders 1, 0, 1, 1, 0, 1 read bottom to top, producing 101101. Checking place values: 32 + 8 + 4 + 1 = 45, confirming the result.

Question 11Computer fundamentals and number systems

Which decimal value does the octal number 17 represent?

  1. 19
  2. 17
  3. 13
  4. 15 Correct answer.

Explanation

In octal the place values are powers of eight, so 17 means 1×8 + 7×1. That sum is 8 + 7 = 15 in decimal.

Question 12Computer fundamentals and number systems

Adding the binary numbers 1011 and 0110 gives:

  1. 10001 Correct answer.
  2. 11101
  3. 10101
  4. 11001

Explanation

Adding bit by bit from the right: 1+0=1, 1+1=0 carry 1, 0+1+1=0 carry 1, 1+0+1=0 carry 1, giving 10001. In decimal this is 11 + 6 = 17, and binary 10001 equals 17.

Question 13Computer fundamentals and number systems

What is the 1's complement of the 8-bit binary number 10110100?

  1. 11001011
  2. 01001011 Correct answer.
  3. 01001100
  4. 10110101

Explanation

The 1's complement is formed by flipping every bit, changing each 0 to 1 and each 1 to 0. Applying this to 10110100 yields 01001011.

Question 14Computer fundamentals and number systems

Which logic gate produces an output of 1 only when both its inputs are 1?

  1. NOT gate
  2. XOR gate
  3. OR gate
  4. AND gate Correct answer.

Explanation

The AND gate outputs 1 only for the input combination 1,1; every other combination gives 0. This matches the logical conjunction of the two inputs.

Question 15Computer fundamentals and number systems

The BCD representation of the decimal number 29 is:

  1. 00101001 Correct answer.
  2. 00011101
  3. 00111001
  4. 00101010

Explanation

In Binary Coded Decimal each decimal digit is coded separately in four bits. The digit 2 becomes 0010 and the digit 9 becomes 1001, so 29 is written as 00101001.

Question 16Computer fundamentals and number systems

Which statement correctly distinguishes RAM from ROM?

  1. RAM permanently stores the bootstrap program while ROM holds user files
  2. RAM is non-volatile while ROM loses its contents when power is removed
  3. ROM is faster than RAM because it stores the operating system
  4. RAM allows both reading and writing during normal operation while ROM is mainly read Correct answer.

Explanation

RAM is read-write memory that loses its contents when power is switched off, whereas ROM is primarily read-only and retains its contents. This read-write versus read-mostly distinction is the key functional difference.

Question 17Computer fundamentals and number systems

A program needs to store a single character such as 'K' in memory. Which code is designed specifically for representing characters?

  1. 1's complement
  2. BCD
  3. Gray code
  4. ASCII Correct answer.

Explanation

ASCII is a character-encoding standard that assigns numeric codes to letters, digits and symbols. BCD, Gray code and complements are numeric representations and do not define character codes.

Question 18Computer fundamentals and number systems

What is the decimal equivalent of the binary fraction 0.101?

  1. 0.75
  2. 0.625 Correct answer.
  3. 0.5
  4. 0.875

Explanation

Bits after the binary point have place values one-half, one-quarter, one-eighth and so on. Here 1×0.5 + 0×0.25 + 1×0.125 = 0.625 in decimal.

Question 19Computer fundamentals and number systems

Which pair of logic expressions is equivalent by De Morgan's law?

  1. NOT (A AND B) equals (NOT A) AND (NOT B)
  2. NOT (A AND B) equals (NOT A) OR (NOT B) Correct answer.
  3. A AND B equals A OR B
  4. NOT (A OR B) equals (NOT A) OR (NOT B)

Explanation

De Morgan's law states that the negation of a conjunction equals the disjunction of the negations. So NOT (A AND B) is equivalent to (NOT A) OR (NOT B).

Question 20Computer fundamentals and number systems

An 8-bit register stores the signed number 11111010 in 2's complement form. Its decimal value is:

  1. -5
  2. -10
  3. -6 Correct answer.
  4. 250

Explanation

In 2's complement the leftmost bit is the sign, so 11111010 is negative. Inverting gives 00000101 and adding 1 gives 00000110, which is 6, so the value is -6.

Question 21Computer fundamentals and number systems

A nibble in computing refers to a group of how many bits, and what hexadecimal digit range can it represent?

  1. 8 bits, representing two hexadecimal digits
  2. 16 bits, representing four hexadecimal digits
  3. 2 bits, representing digits 0 to 3
  4. 4 bits, representing one hexadecimal digit 0 to F Correct answer.

Explanation

A nibble is exactly 4 bits, and four bits can hold 16 distinct patterns (0000 to 1111). These 16 patterns map exactly onto the sixteen hexadecimal digits 0 through F, so one nibble equals one hex digit.

Question 22Computer fundamentals and number systems

The hexadecimal number 2F is added to the hexadecimal number 15. What is the sum in hexadecimal?

  1. 44 Correct answer.
  2. 43
  3. 54
  4. 3A

Explanation

Adding the units column: F (15) + 5 = 20, which is 14 in hexadecimal, so write 4 and carry 1. Adding the sixteens column: 2 + 1 + 1 carry = 4, giving 44 in hexadecimal, equal to 68 in decimal.

Question 23Computer fundamentals and number systems

How many distinct values can be represented with an 8-bit binary number, and what is the largest unsigned value?

  1. 256 values, largest 256
  2. 128 values, largest 127
  3. 256 values, largest 255 Correct answer.
  4. 512 values, largest 511

Explanation

With n bits there are 2^n distinct patterns, so 8 bits give 2^8 = 256 patterns. Counting from zero, the values run 0 to 255, making 255 the largest unsigned value.

Question 24Computer fundamentals and number systems

A logic circuit gives output 1 when inputs A and B differ and output 0 when they are equal. Which gate implements this behaviour, and what is its output when A=1 and B=1?

  1. XOR gate, output 0 Correct answer.
  2. OR gate, output 1
  3. XNOR gate, output 1
  4. AND gate, output 0

Explanation

The exclusive-OR gate outputs 1 only when its inputs are different, so it matches the described behaviour. When both inputs are 1 they are equal, so the XOR output is 0.

Question 25Computer fundamentals and number systems

Which statement best explains why hexadecimal notation is preferred over binary when programmers inspect memory contents?

  1. Hexadecimal arithmetic is faster inside the processor than binary arithmetic
  2. Hexadecimal digits are the only symbols a computer can physically store
  3. Hexadecimal numbers can store values that binary cannot represent
  4. Each hexadecimal digit maps to exactly four bits, so long binary strings become shorter without losing information Correct answer.

Explanation

Because 16 is a power of two, every group of four bits corresponds to one hexadecimal digit, allowing a compact, lossless shorthand for binary. Programmers can convert between the two forms by inspection, which is why hex is used for memory dumps and addresses.

Question 26Computer fundamentals and number systems

In the stored-program concept of a computer, which unit holds the address of the next instruction to be fetched and passes it to the memory unit?

  1. The control unit
  2. The program counter Correct answer.
  3. The arithmetic logic unit
  4. The accumulator

Explanation

The program counter stores the address of the next instruction and sends it to the memory unit so that the instruction can be fetched. The control unit then interprets the fetched instruction, and the ALU performs arithmetic or logical work on data held in the accumulator.

Question 27Computer fundamentals and number systems

A file occupies 3 megabytes of storage. Using the convention that 1 MB = 1024 KB and 1 KB = 1024 bytes, how many bytes does the file occupy?

  1. 3,072,000 bytes
  2. 3,145,700 bytes
  3. 3,000,000 bytes
  4. 3,145,728 bytes Correct answer.

Explanation

Each megabyte contains 1024 × 1024 = 1,048,576 bytes, so three megabytes occupy 3 × 1,048,576 = 3,145,728 bytes. The decimal answer 3,000,000 would apply only if 1 MB were treated as 10^6 bytes.

Question 28Computer fundamentals and number systems

A computer has 12 address lines on its address bus. How many distinct memory locations can the processor address directly?

  1. 24
  2. 4096 Correct answer.
  3. 2048
  4. 144

Explanation

With n address lines, the processor can select 2^n distinct locations, so 12 lines give 2^12 = 4096 addressable locations. The number of lines is an exponent, not a multiplier, so multiplying 12 by 12 or by 2 is incorrect.

Question 29Computer fundamentals and number systems

The 8-bit 2's complement numbers 01101100 and 10110100 are added. Considering the result as an 8-bit 2's complement number, which statement is true?

  1. The sum is 10010000 with no overflow
  2. The sum is 00100000 with no overflow Correct answer.
  3. The sum is 00011111 and overflow has occurred
  4. The sum is 00100000 and overflow has occurred

Explanation

Adding 01101100 (108) and 10110100 (-76) gives 1 0010 0000, and discarding the carry out of the 8-bit register leaves 00100000, which is +32. Overflow occurs only when two operands of the same sign produce a result of the opposite sign, and here the operands have different signs, so no overflow arises.

Question 30Computer fundamentals and number systems

A 4-bit parallel adder is built from four full adders. The carry output of each stage feeds the carry input of the next higher stage. Which limitation of this ripple-carry arrangement is the main reason designers use a carry-lookahead adder instead?

  1. It produces an incorrect sum whenever the final carry-out is 1
  2. It cannot add numbers that contain a 0 bit in the most significant position
  3. It requires a separate adder for subtraction and cannot use 2's complement
  4. Each higher stage must wait for the carry propagated through all lower stages, so the total delay grows with the number of bits Correct answer.

Explanation

In a ripple-carry adder the carry must travel stage by stage, so the worst-case delay is proportional to the number of bits and limits the clock speed of wide adders. A carry-lookahead adder computes carries directly from the propagate and generate signals, reducing that delay.

Question 31Computer hardware, software and operating systems

Which unit of memory is exactly equal to 1024 megabytes (MB)?

  1. One gigabyte (GB) Correct answer.
  2. One kilobyte (KB)
  3. One byte
  4. One terabyte (TB)

Explanation

Computer memory is measured in powers of two, so each larger unit is 1024 times the previous one. A gigabyte therefore equals 1024 megabytes. A kilobyte is only 1024 bytes, and a terabyte is a further 1024 times larger than a gigabyte.

Question 32Computer hardware, software and operating systems

Which of the following is an example of system software rather than application software?

  1. A photo editor
  2. An operating system Correct answer.
  3. A spreadsheet program
  4. A web browser

Explanation

System software manages the hardware and provides a platform on which other programs run; the operating system is the main example. Application software such as spreadsheets, photo editors and browsers is written to help the user perform a particular task.

Question 33Computer hardware, software and operating systems

In a computer, which component is described as the 'brain' that fetches, decodes and executes instructions?

  1. The CPU Correct answer.
  2. The RAM module
  3. The hard disk
  4. The monitor

Explanation

The Central Processing Unit carries out the fetch-decode-execute cycle for every instruction. Storage and RAM only hold data and programs, and the monitor only displays output. The arithmetic and control work that defines processing happens inside the CPU.

Question 34Computer hardware, software and operating systems

Which of these devices is an input device?

  1. Speaker
  2. Projector
  3. Scanner Correct answer.
  4. Plotter

Explanation

A scanner takes a printed page and converts it into digital data for the computer, so it feeds data in. Plotters, speakers and projectors all take signals from the computer and present them to the user, making them output devices.

Question 35Computer hardware, software and operating systems

Which of the following is an example of an open-source operating system?

  1. macOS
  2. Windows 11
  3. Linux Correct answer.
  4. MS-DOS

Explanation

Open-source software makes its source code freely available so anyone may study, modify and redistribute it; Linux is the best-known open-source operating system. Windows, macOS and MS-DOS are proprietary products whose source code is controlled by their owners.

Question 36Computer hardware, software and operating systems

Which of the following is volatile memory, whose contents are lost when the power is switched off?

  1. Hard disk
  2. RAM Correct answer.
  3. DVD
  4. ROM

Explanation

RAM is volatile: it needs continuous power to hold its contents and is cleared on shutdown. ROM is non-volatile and keeps its contents permanently, and magnetic or optical storage such as hard disks and DVDs also retain data without power.

Question 37Computer hardware, software and operating systems

A file named 'report.txt' is stored on a disk. Which part of this name identifies the type of file?

  1. txt Correct answer.
  2. The full name
  3. The dot only
  4. report

Explanation

A file name has a base name followed by an extension after the dot. Here 'report' is the base name and 'txt' is the extension, which tells the operating system and the user what kind of content the file holds.

Question 38Computer hardware, software and operating systems

Which of the following best describes the function of an operating system's file management?

  1. It converts source code into machine code
  2. It increases the clock speed of the processor
  3. It displays images on the monitor
  4. It organises, stores and retrieves files on storage devices Correct answer.

Explanation

File management in an operating system creates, names, stores, locates and deletes files and folders on storage media. Compilation is done by language translators, clock speed is fixed by hardware, and display is handled by output devices and drivers.

Question 39Computer hardware, software and operating systems

A student wants to keep a program and its data permanently even after the computer is switched off. Which type of memory should be used?

  1. Registers
  2. RAM
  3. Cache memory
  4. Secondary storage Correct answer.

Explanation

Permanent retention needs non-volatile secondary storage such as a hard disk or SSD. Cache memory, registers and RAM are all volatile and lose their contents when power is removed, so they cannot keep data permanently.

Question 40Computer hardware, software and operating systems

Which of the following is the correct order of the stages in the machine cycle of a CPU?

  1. Fetch, decode, execute Correct answer.
  2. Execute, decode, fetch
  3. Fetch, execute, decode
  4. Decode, fetch, execute

Explanation

The CPU first fetches the instruction from memory, then decodes it to find out what operation is required, and finally executes it. Only after execution does it move on to the next instruction.

Question 41Computer hardware, software and operating systems

Which of these is a function performed by the operating system rather than by application software?

  1. Typing a letter for printing
  2. Editing a digital photograph
  3. Scheduling processes on the CPU Correct answer.
  4. Preparing a monthly budget sheet

Explanation

Process scheduling decides which program gets the processor and when, and that control belongs to the operating system's resource management. Budget sheets, photo editing and letter typing are tasks done by application programs running on top of the operating system.

Question 42Computer hardware, software and operating systems

A user wants to install a new printer on a Windows computer. What is the role of the device driver in this process?

  1. It supplies electrical power to the printer
  2. It stores the documents that are waiting to be printed
  3. It translates instructions from the operating system into commands the printer understands Correct answer.
  4. It converts the document into a permanent image file

Explanation

A device driver is software that sits between the operating system and a specific hardware device and converts general commands into signals that device can act on. Without a suitable driver the printer cannot be controlled correctly. Storing documents and supplying power are separate hardware or software functions.

Question 43Computer hardware, software and operating systems

Which of the following statements about a Graphical User Interface (GUI) is correct?

  1. It replaces the need for an operating system
  2. It requires the user to type commands only
  3. It can only be used on mainframe computers
  4. It uses icons, windows and menus that the user can point at and click Correct answer.

Explanation

A GUI presents visual elements such as icons, windows, menus and pointers so users can give instructions by clicking rather than by typing commands. Command-line interfaces rely on typed commands, and a GUI is itself part of the operating system's user interface, not a replacement for it.

Question 44Computer hardware, software and operating systems

A user deletes a file in Windows and it moves to the Recycle Bin. What does this tell you about the file?

  1. The file has been permanently erased from the disk
  2. The file has been renamed and hidden
  3. The file has been compressed to save space
  4. The file has been moved to a temporary holding area and can be restored Correct answer.

Explanation

The Recycle Bin is a temporary holding area that keeps deleted files until the user either restores them or empties the bin. The file's data still exists on the disk, so it can be recovered. Permanent erasure only happens after the bin is emptied.

Question 45Computer hardware, software and operating systems

Which of the following pairs correctly matches a memory type with its usual characteristic?

  1. ROM - contents can be freely rewritten by the user during normal use
  2. RAM - contents are read-only and cannot be changed
  3. RAM - contents are retained when power is removed
  4. ROM - contents are retained when power is removed Correct answer.

Explanation

ROM, read-only memory, is non-volatile: it keeps its stored instructions even when the power is switched off, which is why firmware is kept there. RAM is the opposite, being volatile and freely writable while the computer runs.

Question 46Computer hardware, software and operating systems

A computer has 4 GB of RAM and runs several large programs at once, becoming very slow. Which explanation is most reasonable?

  1. The keyboard is sending too many characters
  2. The operating system uses virtual memory on the hard disk, which is much slower than RAM Correct answer.
  3. The monitor has too few colours
  4. The printer driver is missing

Explanation

When the programs in use need more memory than the installed RAM can hold, the operating system moves data to a swap area on secondary storage, called virtual memory. Because the hard disk is far slower than RAM, this paging makes the system slow. Display, keyboard and printer issues do not explain overall slowness.

Question 47Computer hardware, software and operating systems

In a Windows environment, which file name would the operating system reject?

  1. notes_2024.txt
  2. data:final.csv Correct answer.
  3. photo1.jpg
  4. my report.docx

Explanation

Windows does not allow certain reserved characters in file names, and the colon is one of them because it is used for drive letters. Therefore 'data:final.csv' is invalid. Underscores, spaces and ordinary letters and digits are all allowed.

Question 48Computer hardware, software and operating systems

A program is described as being written in a high-level language. What does this mean for the computer?

  1. It can run only on mainframe computers
  2. It does not need an operating system to run
  3. It can be executed directly by the CPU without any translation
  4. It must be converted into machine code by a compiler or interpreter before execution Correct answer.

Explanation

High-level languages use English-like statements that people can read and write easily, but the CPU only understands its own machine code. A translator, either a compiler or an interpreter, converts the program into machine instructions before it can run.

Question 49Computer hardware, software and operating systems

Which statement correctly distinguishes a compiler from an interpreter?

  1. A compiler is hardware, while an interpreter is software
  2. A compiler translates the whole program at once, while an interpreter translates and runs it line by line Correct answer.
  3. A compiler translates line by line, while an interpreter translates the whole program at once
  4. A compiler runs the program, while an interpreter only stores it

Explanation

A compiler reads the entire source program and produces a complete machine-code object program before anything runs. An interpreter takes one statement at a time, translates it and immediately carries it out, so errors are reported as they are reached.

Question 50Computer hardware, software and operating systems

An operating system uses pre-emptive multitasking. What does this imply about a running program?

  1. It must be written in machine code
  2. It may be interrupted by the operating system so another program can use the CPU Correct answer.
  3. It keeps the CPU until it finishes on its own
  4. It cannot be stored in RAM while running

Explanation

In pre-emptive multitasking the operating system gives each process a time slice and forcibly takes back the CPU when the slice ends. This allows several programs to share the processor fairly without any one of them holding it indefinitely. Non-pre-emptive systems, by contrast, wait for a program to give up the CPU.