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Cameroon GCE O-Level Computer Science study materials
Cameroon GCE O-Level Computer Science study resources

Cameroon GCE O-Level Computer Science practice questions

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Question 1Computer hardware and organisation: CPU, memory, input/output devices, storage media

Which component of the CPU performs arithmetic such as addition and subtraction?

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

Explanation

The arithmetic logic unit (ALU) is the part of the processor that carries out arithmetic operations like addition and subtraction and logical operations like AND, OR and comparison. The other listed units handle sequencing and storage of instructions rather than calculation.

Question 2Computer hardware and organisation: CPU, memory, input/output devices, storage media

Which type of memory loses its stored data when the computer is switched off?

  1. A hard disk drive
  2. ROM
  3. Flash memory
  4. Volatile memory such as RAM Correct answer.

Explanation

Volatile memory, of which RAM is the main example, needs a continuous power supply to keep its contents, so data disappears when power is removed. Non-volatile media keep data without power.

Question 3Computer hardware and organisation: CPU, memory, input/output devices, storage media

A user wants to type a long report into a word processor. Which input device is most suitable?

  1. A graphics tablet
  2. A keyboard Correct answer.
  3. A barcode reader
  4. A joystick

Explanation

Entering large amounts of text is fastest and most accurate with a keyboard, which is designed for character input. The other devices are specialised for drawing, coded data capture or game control.

Question 4Computer hardware and organisation: CPU, memory, input/output devices, storage media

Which storage medium uses laser light to read and write data?

  1. Hard disk platter
  2. Solid-state drive
  3. Optical disc Correct answer.
  4. Magnetic tape

Explanation

Optical discs such as CDs, DVDs and Blu-ray discs store data as pits and lands that are read by a laser beam. Magnetic and solid-state media use different physical principles.

Question 5Computer hardware and organisation: CPU, memory, input/output devices, storage media

Which unit measures the clock speed of a processor?

  1. Volts
  2. Hertz Correct answer.
  3. Dots per inch
  4. Megabytes

Explanation

Clock speed is the number of cycles the processor completes each second, so it is measured in hertz and its multiples such as gigahertz. The other units measure capacity, voltage or print resolution.

Question 6Computer hardware and organisation: CPU, memory, input/output devices, storage media

What is the main function of main memory (RAM) in a computer system?

  1. To hold programs and data currently in use Correct answer.
  2. To convert analogue signals to digital form
  3. To permanently archive files
  4. To supply electrical power to the CPU

Explanation

RAM holds the instructions and data of programs that are running so the CPU can access them quickly. It is volatile working storage, not permanent archive storage, and it neither converts signals nor supplies power.

Question 7Computer hardware and organisation: CPU, memory, input/output devices, storage media

Which of these is an output device?

  1. A light pen
  2. A microphone
  3. A scanner
  4. A plotter Correct answer.

Explanation

A plotter produces large, precise drawings on paper, so it sends data out of the computer. The other three devices bring data into the computer.

Question 8Computer hardware and organisation: CPU, memory, input/output devices, storage media

Which memory is normally used to store the start-up instructions that a computer runs when it is powered on?

  1. ROM Correct answer.
  2. RAM
  3. Virtual memory
  4. Cache memory

Explanation

The start-up routine is held in read-only memory so that it is present immediately at power-on and cannot be lost. RAM, cache and virtual memory are volatile working storage that is empty at start-up.

Question 9Computer hardware and organisation: CPU, memory, input/output devices, storage media

A school needs to distribute the same 4 GB video lesson to 200 students who each have a USB port. Which storage medium is the most practical to give each student?

  1. A 3.5-inch floppy disk
  2. A USB flash drive Correct answer.
  3. A magnetic tape cartridge
  4. A Blu-ray disc

Explanation

A USB flash drive is small, cheap, rewritable and plugs directly into a standard USB port, making it practical for handing out copies to many students. The alternatives are either low-capacity, require a special drive, or are not suited to individual distribution.

Question 10Computer hardware and organisation: CPU, memory, input/output devices, storage media

During the fetch part of the fetch-decode-execute cycle, what happens first?

  1. The instruction at the address in the program counter is copied to the processor Correct answer.
  2. The result is written back to memory
  3. The ALU adds two operands
  4. The control unit decodes the opcode

Explanation

Fetching means retrieving the instruction whose address is held in the program counter and placing it into the instruction register for decoding. Arithmetic, decoding and write-back occur in later stages of the cycle.

Question 11Computer hardware and organisation: CPU, memory, input/output devices, storage media

Which statement best describes the purpose of cache memory in a processor?

  1. It provides fast access to frequently used instructions and data Correct answer.
  2. It converts machine code into assembly language
  3. It stores the operating system permanently
  4. It increases the number of cores in the CPU

Explanation

Cache is small, very fast memory close to the CPU that keeps recently or frequently used instructions and data so that slower main memory is accessed less often. It does not store the operating system, add cores or translate code.

Question 12Computer hardware and organisation: CPU, memory, input/output devices, storage media

A company must keep daily backups of 20 terabytes of data and restore them only in an emergency. Which storage medium is most cost-effective for this purpose?

  1. Cache memory
  2. CD-R
  3. Solid-state drive
  4. Magnetic tape Correct answer.

Explanation

Magnetic tape offers very high capacity at low cost per gigabyte and suits sequential backup and archive work where fast random access is not needed. The other options are either expensive per gigabyte, tiny in capacity, or not storage media for backup.

Question 13Computer hardware and organisation: CPU, memory, input/output devices, storage media

Why does a computer with more RAM generally run several large applications more smoothly than one with less RAM?

  1. More RAM increases the clock speed of the processor
  2. More RAM reduces the need to swap data to slower secondary storage Correct answer.
  3. More RAM raises the resolution of the monitor
  4. More RAM eliminates the need for an operating system

Explanation

With more RAM, more programs and their data can stay in main memory at once, so the system swaps to the much slower disk less often and response times improve. RAM capacity does not change clock speed, screen resolution or the need for an operating system.

Question 14Computer hardware and organisation: CPU, memory, input/output devices, storage media

Which device would a supermarket use to read the price code printed on a product at the checkout?

  1. Magnetic ink character reader
  2. Optical mark reader
  3. Plotter
  4. Barcode scanner Correct answer.

Explanation

A barcode scanner shines light on the printed bars and interprets the reflected pattern to identify the product quickly and accurately. The other devices read pencil marks, special magnetic characters or produce output.

Question 15Computer hardware and organisation: CPU, memory, input/output devices, storage media

Which of the following is a characteristic of a solid-state drive compared with a magnetic hard disk drive?

  1. It has moving read/write heads
  2. It stores data on spinning platters
  3. It has no moving parts and is more shock-resistant Correct answer.
  4. It uses laser light to read data

Explanation

A solid-state drive stores data in flash memory chips, so it has no moving mechanical parts, giving faster access and greater resistance to shock. Hard disks use spinning platters and moving heads, while optical media use lasers.

Question 16Computer hardware and organisation: CPU, memory, input/output devices, storage media

What is the role of the control unit during program execution?

  1. It performs the arithmetic calculations
  2. It stores the results of calculations permanently
  3. It fetches, decodes and coordinates the execution of instructions Correct answer.
  4. It displays output on the monitor

Explanation

The control unit directs the operation of the processor by fetching instructions, decoding them and sending control signals to the other units that carry them out. Calculation, permanent storage and display are handled by other components.

Question 17Computer hardware and organisation: CPU, memory, input/output devices, storage media

A student says a 3 GHz processor is always faster than a 2 GHz processor for every task. Which factor most weakens this claim?

  1. Different processors may complete a different number of instructions per clock cycle Correct answer.
  2. Processors do not have a clock
  3. A 3 GHz processor uses less power
  4. Clock speed is measured in hertz

Explanation

Overall performance depends on how much work is done per clock cycle as well as on clock speed, so a processor with a richer instruction set or more cores can outperform one with a higher clock. Clock speed alone does not determine speed for every task.

Question 18Computer hardware and organisation: CPU, memory, input/output devices, storage media

Which combination correctly pairs a device with its category?

  1. Touchscreen with output only
  2. Printer with input
  3. Sensor in a traffic counter with input Correct answer.
  4. Speaker with input

Explanation

A sensor detects a physical quantity such as the passing of a vehicle and sends that data into the computer, so it is an input device. A touchscreen is both input and output, a speaker is output only, and a printer is output only.

Question 19Computer hardware and organisation: CPU, memory, input/output devices, storage media

Why is secondary storage needed in a computer even though RAM is much faster?

  1. Secondary storage is faster than cache memory
  2. Secondary storage is volatile and backs up the RAM
  3. Secondary storage keeps data permanently when power is off Correct answer.
  4. Secondary storage replaces the need for a CPU

Explanation

RAM is volatile and limited in size, so programs and files must be kept permanently on secondary storage such as a hard disk or flash drive and loaded into RAM when needed. Secondary storage does not replace the processor and is slower than RAM and cache.

Question 20Computer hardware and organisation: CPU, memory, input/output devices, storage media

In a computer, which bus carries the address of the memory location that the processor wants to access?

  1. The control bus
  2. The address bus Correct answer.
  3. The data bus
  4. The power bus

Explanation

The address bus is a one-way set of lines that carries the location identifier from the processor to memory or a device. The data bus carries the contents, the control bus carries signals such as read and write, and there is no power bus in this model.

Question 21Computer hardware and organisation: CPU, memory, input/output devices, storage media

A hospital must keep patient scan images for many years and retrieve any individual image quickly. Which storage solution best meets both requirements?

  1. A single large RAM module
  2. A hard disk array with a backup system Correct answer.
  3. Magnetic tape only, with no index
  4. Write-once CD-R discs stored in a cupboard

Explanation

A disk array gives fast random access to individual images and large capacity, and a backup system protects the long-term archive. RAM cannot retain data without power, CD-R discs are slow and awkward to search, and unindexed tape gives very slow retrieval.

Question 22Computer hardware and organisation: CPU, memory, input/output devices, storage media

A program's working set is slightly larger than the available RAM. What is the most likely effect on performance?

  1. The processor clock speed will increase automatically
  2. The monitor resolution will drop
  3. The program will run faster because more data is in RAM
  4. The system will use virtual memory and slow down because of disk access Correct answer.

Explanation

When the working set exceeds physical RAM, the operating system moves pages to disk as virtual memory, and frequent paging to slower secondary storage increases access time and slows execution. Clock speed and display resolution are unaffected by memory pressure.

Question 23Computer hardware and organisation: CPU, memory, input/output devices, storage media

Which statement about the relationship between the fetch-decode-execute cycle and the program counter is correct?

  1. The program counter stores the opcode of the current instruction
  2. The program counter holds the result of the last calculation
  3. The program counter is incremented during fetch so that the next instruction can be located Correct answer.
  4. The program counter is only used during the execute stage

Explanation

The program counter holds the address of the next instruction; it is incremented as part of the fetch stage so that the following cycle can locate the next instruction. Results are held in registers such as the accumulator, and opcodes are held in the instruction register.

Question 24Computer hardware and organisation: CPU, memory, input/output devices, storage media

A manufacturer wants a device that is cheap, has no moving parts, uses little power and can retain firmware when switched off. Which memory technology best fits?

  1. Dynamic RAM
  2. Static RAM
  3. Flash memory Correct answer.
  4. Magnetic core memory

Explanation

Flash memory is non-volatile, has no moving parts, uses little power and is inexpensive, which is why it is used for firmware and portable storage. DRAM and SRAM are volatile and need power, and core memory is obsolete.

Question 25Computer hardware and organisation: CPU, memory, input/output devices, storage media

Two computers have the same clock speed and RAM, but one completes a video-rendering task much faster. Which explanation is most plausible?

  1. The faster computer uses a higher-capacity hard disk
  2. The faster computer has a larger monitor
  3. The faster computer has a lower-resolution printer
  4. The faster computer has a larger cache and more cores available to the renderer Correct answer.

Explanation

Rendering is highly parallel and memory-intensive, so more cores and a larger cache can greatly reduce execution time even at the same clock speed. Monitor size, disk capacity and printer resolution do not affect processing speed.

Question 26Computer hardware and organisation: CPU, memory, input/output devices, storage media

A technician compares two printers. One fires small nozzles to spray droplets of ink onto paper, while the other melts a powdered substance onto the paper. Which pair correctly names these two printer types?

  1. Laser printer and inkjet printer
  2. Inkjet printer and laser printer Correct answer.
  3. Plotter and line printer
  4. Dot-matrix printer and thermal printer

Explanation

An inkjet printer works by forcing tiny droplets of liquid ink through nozzles onto the page, so it is a non-impact printer. A laser printer forms the image with toner powder that is fused onto the paper using heat and pressure. The two descriptions in the stem therefore match inkjet and laser respectively.

Question 27Computer hardware and organisation: CPU, memory, input/output devices, storage media

Which statement correctly describes the difference between volatile and non-volatile memory?

  1. Volatile memory can only be read from, while non-volatile memory can only be written to.
  2. Volatile memory loses its contents when power is removed, while non-volatile memory keeps its contents without power. Correct answer.
  3. Volatile memory is always slower than non-volatile memory in every situation.
  4. Volatile memory keeps its contents without power, while non-volatile memory loses its contents when power is removed.

Explanation

Volatility refers to what happens to stored data when the power supply is cut. RAM is volatile because its contents vanish at power-off, whereas ROM, flash memory and magnetic disks are non-volatile and retain data. This distinction explains why programs and files must be saved to secondary storage before a computer is switched off.

Question 28Computer hardware and organisation: CPU, memory, input/output devices, storage media

A processor has a 16-bit address bus and each addressable memory location holds one byte. What is the maximum amount of memory the processor can address directly?

  1. 16 kilobytes
  2. 64 kilobytes Correct answer.
  3. 128 kilobytes
  4. 32 kilobytes

Explanation

With n address lines the processor can form 2^n distinct addresses. For 16 lines this gives 2^16 = 65,536 addresses, and at one byte per address that equals 65,536 bytes, which is 64 KB. The width of the data bus affects how much is moved per transfer, not how many locations can be selected.

Question 29Computer hardware and organisation: CPU, memory, input/output devices, storage media

A user complains that a computer becomes extremely slow whenever several large programs are open at once, and the disk activity light stays on almost continuously. Which explanation best fits these symptoms?

  1. The processor clock speed has fallen permanently because the cache has been filled with program data.
  2. The keyboard buffer is full because too many keystrokes have been typed.
  3. The monitor resolution is too high for the graphics hardware to refresh the screen.
  4. The programs do not all fit in RAM, so the system is continually swapping pages to and from secondary storage. Correct answer.

Explanation

When the combined working sets of running programs exceed available RAM, the operating system moves pages out to disk and back again, a process called swapping or paging. Because secondary storage is far slower than RAM, the machine appears to stall, and the constant transfers keep the disk busy. Adding RAM reduces the need to swap and restores responsiveness.

Question 30Computer hardware and organisation: CPU, memory, input/output devices, storage media

An embedded controller must hold its control program permanently, allow that program to be updated occasionally in the field, and keep the program when power is removed. Which memory technology best meets all three requirements?

  1. Dynamic RAM
  2. A magnetic tape cartridge
  3. Static RAM
  4. Flash memory Correct answer.

Explanation

Flash memory is non-volatile, so it retains the control program without power, and it can be erased and rewritten electrically, allowing firmware updates. It is also cheap, compact and shock-resistant, which suits embedded controllers. DRAM and SRAM are volatile and would lose the program at power-off, while tape does not permit convenient random access or in-place updating.

Question 31Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

How is the decimal number 45 written in binary?

  1. 101101 Correct answer.
  2. 101011
  3. 100111
  4. 110101

Explanation

Repeated division by two gives remainders 1,0,1,1,0,1 read upwards, so 45 = 32+8+4+1 = 101101. Checking the place values 32+8+4+1 confirms the total is 45.

Question 32Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

What is the denary value of the binary number 11001?

  1. 19
  2. 25 Correct answer.
  3. 27
  4. 23

Explanation

The bits from left to right carry place values 16, 8, 4, 2 and 1. Adding those with a 1 gives 16+8+1 = 25.

Question 33Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

Which octal value is equivalent to the binary number 101110?

  1. 46
  2. 54
  3. 56 Correct answer.
  4. 67

Explanation

Group the bits in threes from the right: 101 110. These groups are 5 and 6, so the octal form is 56.

Question 34Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

What is the hexadecimal representation of the denary number 202?

  1. AC
  2. C2
  3. A2
  4. CA Correct answer.

Explanation

202 divided by 16 gives 12 remainder 10. Twelve is C and ten is A, so the hexadecimal form is CA.

Question 35Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

In the ASCII character set, what does the code 65 represent?

  1. The capital letter A Correct answer.
  2. The digit 5
  3. The capital letter E
  4. The space character

Explanation

In standard ASCII the capital letters begin at 65, so 65 is 'A' and 90 is 'Z'. Digits begin at 48 and the space character is 32.

Question 36Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

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

  1. OR gate
  2. NOR gate
  3. AND gate Correct answer.
  4. XOR gate

Explanation

The AND gate outputs 1 solely for the input combination 1,1; every other combination gives 0. The OR, XOR and NOR gates all output 1 for at least one input combination containing a 0.

Question 37Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

Which statement correctly distinguishes a bit from a byte?

  1. A byte holds two bits and a bit holds two nibbles.
  2. A bit is a single binary digit and a byte is eight bits. Correct answer.
  3. A byte is a single binary digit and a bit is eight of them.
  4. A bit and a byte both hold exactly four binary digits.

Explanation

A bit is one binary digit, either 0 or 1, and it is the smallest unit of data. A byte groups eight bits together, which is why one byte can store 256 different values.

Question 38Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

What is the denary value of the hexadecimal number 2F?

  1. 47 Correct answer.
  2. 63
  3. 45
  4. 31

Explanation

The digit 2 sits in the sixteens column and F stands for 15. So the value is 2x16 + 15 = 47.

Question 39Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

A binary number is 11110000. What is its value in hexadecimal?

  1. E0
  2. F8
  3. 0F
  4. F0 Correct answer.

Explanation

Split the byte into two nibbles: 1111 and 0000. The nibble 1111 is 15, written F, and 0000 is 0, giving F0.

Question 40Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

What is the result of adding the binary numbers 1011 and 0110?

  1. 11001
  2. 10011
  3. 10101
  4. 10001 Correct answer.

Explanation

Adding column by column from the right: 1+0=1, 1+1=0 carry 1, 0+1+1=0 carry 1, and 1+0+1=0 carry 1, giving 10001. In denary this is 11+6=17, which matches 10001.

Question 41Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

In two's complement using 8 bits, which binary pattern represents -5?

  1. 11111010
  2. 00000101
  3. 11111011 Correct answer.
  4. 10000101

Explanation

Start with +5 as 00000101, invert the bits to 11111010, then add 1 to get 11111011. This pattern has a leading 1, confirming a negative value.

Question 42Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

A computer uses 8-bit two's complement integers. What denary value does the pattern 10000000 represent?

  1. -128 Correct answer.
  2. -0
  3. -127
  4. 128

Explanation

In 8-bit two's complement the most negative value is 10000000, which equals -128. The range runs from -128 to +127, so +128 cannot be stored.

Question 43Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

Which statement about Unicode compared with ASCII is correct?

  1. Unicode and ASCII assign identical codes to every character.
  2. Unicode can only store digits and punctuation, not letters.
  3. Unicode uses fewer bits per character than ASCII.
  4. Unicode can represent characters from many writing systems, while ASCII is limited to 128 codes. Correct answer.

Explanation

Standard ASCII defines only 128 code points, covering basic Latin letters, digits and control codes. Unicode provides a much larger code space so that characters from many languages and symbol sets can be represented consistently.

Question 44Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

Which logic gate outputs 1 when its two inputs are different and 0 when they are the same?

  1. XOR gate Correct answer.
  2. NAND gate
  3. XNOR gate
  4. AND gate

Explanation

The exclusive-OR gate gives 1 for the input pairs 0,1 and 1,0 and gives 0 for 0,0 and 1,1. It therefore detects when the inputs differ.

Question 45Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

A 3-input AND gate has inputs 1, 0 and 1. What is its output?

  1. It oscillates between 0 and 1
  2. It is undefined
  3. 1
  4. 0 Correct answer.

Explanation

An AND gate outputs 1 only when every input is 1. Because one input is 0, the output must be 0 regardless of the other two inputs.

Question 46Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

Which truth table row correctly gives the outputs of a NAND gate followed by a NOT gate for inputs A=1 and B=1?

  1. NAND gives 0 and the NOT gate gives 1 Correct answer.
  2. NAND gives 1 and the NOT gate gives 0
  3. NAND gives 1 and the NOT gate gives 1
  4. NAND gives 0 and the NOT gate gives 0

Explanation

For inputs 1,1 the AND result is 1, so NAND inverts it to 0. Feeding 0 into the NOT gate produces 1, so the combined circuit behaves as an AND gate.

Question 47Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

What is the octal representation of the denary number 100?

  1. 64
  2. 144 Correct answer.
  3. 110
  4. 124

Explanation

Dividing 100 by 8 gives 12 remainder 4, then 12 by 8 gives 1 remainder 4, then 1 by 8 gives 0 remainder 1. Reading remainders upwards gives 144, which checks as 1x64 + 4x8 + 4 = 100.

Question 48Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

A colour is stored as the hexadecimal value #3A9F. What is the binary form of this 16-bit value?

  1. 0011101011111001
  2. 0111101010011111
  3. 0011001110101111
  4. 0011101010011111 Correct answer.

Explanation

Each hexadecimal digit expands to four bits: 3=0011, A=1010, 9=1001 and F=1111. Joining these nibbles gives 0011101010011111.

Question 49Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

A program stores a student's age in an 8-bit unsigned field. What is the largest value it can hold?

  1. 255 Correct answer.
  2. 128
  3. 127
  4. 256

Explanation

With 8 bits there are 2 to the power 8, that is 256, distinct patterns. Because an unsigned field includes zero, the range runs from 0 to 255.

Question 50Number systems and data representation: binary, octal, hexadecimal, character coding, logic gates

The binary number 1101101 is to be stored in one byte. Which statement is true?

  1. It needs two leading zeros to fit in a byte.
  2. It needs one leading zero to fit in a byte. Correct answer.
  3. It cannot be stored in a byte because it exceeds 255.
  4. It fits exactly in one byte with no padding needed.

Explanation

The number has seven bits, and one byte holds eight bits, so a single leading zero is added to give 01101101. Its value is 109, well within the byte range.