Karinoya Learning Room

Qualifications · IT Passport Success Lab

Computer Systems

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Q1 | Role of the CPU

Among the units composing a computer, which of the following appropriately describes the CPU, the central processing unit?

  1. It presents processing results on screens or paper in a form people can read
  2. It stores large amounts of data for long periods so that they are not lost when the power is turned off
  3. It reads and interprets program instructions, performing arithmetic and controlling other units
  4. It brings characters and numbers entered by the user into the computer
AnswerC. It reads and interprets program instructions, performing arithmetic and controlling other units

The CPU is the unit responsible for interpreting instructions, computing, and controlling, the brain of the computer. The second option describes auxiliary storage, the third an input device, and the fourth an output device. The CPU does not itself do the storing or the input and output; its role is to direct those units.

Q2 | Clock frequency

What does it mean for a CPU's clock frequency to be 2GHz?

  1. It can transfer 2 billion bytes of data per second
  2. It ticks 200 million clock cycles per second
  3. It ticks 2 billion clock cycles per second
  4. It can execute 200 million instructions per second
AnswerC. It ticks 2 billion clock cycles per second

1GHz means 1 billion times per second, so 2GHz means ticking 2 billion clock cycles. The first option is off by a factor of 10. The clock is the rhythm of operation, and since one instruction takes multiple clock cycles, it does not equal the instruction count as in the third option. The fourth is about data transfer volume, a different metric from clock frequency.

Q3 | Multi-core

Which of the following appropriately describes a multi-core processor?

  1. A setup that installs multiple CPUs in one computer and divides the processing among them
  2. A structure that puts multiple computing cores inside a single CPU
  3. A mechanism that places fast memory between the CPU and main memory to reduce waiting time
  4. A technology that runs multiple virtual computers on one physical computer
AnswerB. A structure that puts multiple computing cores inside a single CPU

A multi-core processor has multiple cores, the central computing parts, inside a single CPU. The first option describes a multiprocessor, which differs in mounting multiple CPUs themselves. The second is cache memory and the fourth is virtualization; neither has anything to do with the number of cores.

Q4 | GPU

Which of the following is an appropriate characteristic of a GPU?

  1. It excels at executing large numbers of simple calculations simultaneously and is used for image processing and AI computation
  2. It is software that mediates between the OS and peripheral devices and controls the devices
  3. Its contents survive power-off, making it suitable for storing boot programs
  4. It combines multiple magnetic disks to act as one, raising reliability
AnswerA. It excels at executing large numbers of simple calculations simultaneously and is used for image processing and AI computation

A GPU is a device that executes many operations in parallel for image processing, and thanks to that trait it is also used for massive computations such as AI training. The first option describes ROM, the second a device driver, and the third RAID; none has anything to do with GPUs.

Q5 | Instruction cycle

Which of the following puts the steps by which a CPU processes one instruction in the correct order?

  1. Fetch the instruction, then decode it, then execute it, then store the result
  2. Execute the instruction, then fetch it, then decode it, then store the result
  3. Decode the instruction, then fetch the instruction, then execute it, then store the result
  4. Fetch the instruction, then execute it, then decode it, then store the result
AnswerA. Fetch the instruction, then decode it, then execute it, then store the result

The CPU first fetches the instruction from main memory, then decodes its content, then reads the necessary data and executes it, and finally stores the result. Decoding before fetching is impossible, so the first and fourth options are wrong, and executing without decoding is also impossible, so the third is wrong too.

Q6 | Instruction throughput

A CPU has a clock frequency of 2GHz and takes an average of 4 clock cycles to execute one instruction. Approximately how many instructions can this CPU execute per second?

  1. 8 billion instructions
  2. 2 billion instructions
  3. 500 million instructions
  4. 250 million instructions
AnswerC. 500 million instructions

2GHz means 2×10^9 clock cycles per second, and one instruction needs 4 cycles, so 2×10^9 ÷ 4 = 5×10^8, that is, 500 million instructions. 250 million comes from dividing by 8 instead of 4, 2 billion treats the clock count itself as the instruction count, and 8 billion multiplies by 4 instead of dividing; all are wrong.

Q7 | RAM and ROM

Which of the following is an appropriate statement about RAM and ROM?

  1. RAM is non-volatile and ROM is volatile
  2. Both RAM and ROM lose their contents when the power is turned off
  3. RAM loses its contents when the power is turned off, while ROM retains its contents even with the power off
  4. ROM is used as main memory to hold programs during execution
AnswerC. RAM loses its contents when the power is turned off, while ROM retains its contents even with the power off

RAM is volatile and loses its contents at power-off, while ROM is non-volatile and retains its contents with the power off. The first option reverses the descriptions, and the second is wrong about ROM. Main memory holding running programs uses RAM, so the third is also wrong.

Q8 | DRAM and SRAM

Which of the following is an appropriate comparison of DRAM and SRAM?

  1. DRAM is faster than SRAM, so it is used for cache memory
  2. SRAM requires refresh operations to retain its stored contents
  3. DRAM is inexpensive and easy to make high-capacity, and is used for main memory
  4. SRAM is non-volatile memory whose contents survive power-off
AnswerC. DRAM is inexpensive and easy to make high-capacity, and is used for main memory

DRAM has a simple structure that makes large capacity cheap, so it is used for main memory. SRAM is the faster one and is used for cache memory, so the first option is reversed, and it is DRAM that needs refreshing, so the second is wrong. SRAM is also a kind of RAM and is volatile, so the fourth is wrong as well.

Q9 | Flash memory

Which storage element is used in USB memory sticks, SD cards, and SSDs?

  1. Mask ROM
  2. DRAM
  3. Flash memory
  4. SRAM
AnswerC. Flash memory

Flash memory is non-volatile memory that can be electrically erased and rewritten in block units, and it is used in USB memory sticks, SD cards, and SSDs. DRAM and SRAM are volatile and lose their contents at power-off, so they cannot serve for storage. Mask ROM has its contents fixed at manufacture and cannot be rewritten, so it is unsuitable.

Q10 | Mask ROM

Which of the following appropriately describes mask ROM?

  1. Its contents are written in at the manufacturing stage and cannot be rewritten afterwards
  2. It can be rewritten without ultraviolet exposure and has no limit on the number of rewrites
  3. It loses its contents when the power is turned off, so it is used as main memory
  4. Users can electrically rewrite its contents any number of times
AnswerA. Its contents are written in at the manufacturing stage and cannot be rewritten afterwards

Mask ROM is ROM whose contents are built in at manufacture; it cannot be rewritten after shipment, and mass production makes the unit price low. The first option is a characteristic of EEPROM and flash memory. ROM is non-volatile, so the second is wrong, and memory with no rewrite limit as in the third is not typical, while mask ROM cannot be rewritten at all.

Q11 | Cache memory

Which of the following is an appropriate purpose of providing cache memory?

  1. To reduce the waiting time caused by the speed gap between the CPU and main memory, speeding up processing
  2. To keep data from being lost when the power is turned off
  3. To use part of auxiliary storage as if it were main memory when main memory capacity runs short
  4. To spread data across multiple disks in preparation for failures
AnswerA. To reduce the waiting time caused by the speed gap between the CPU and main memory, speeding up processing

Cache memory is small, fast memory placed between the CPU and main memory, holding frequently used data to reduce waiting time. The second option is the role of non-volatile memory, the third describes virtual memory, and the fourth describes RAID; none is the purpose of cache memory.

Q12 | Memory hierarchy

Which of the following arranges registers, cache memory, main memory, and auxiliary storage in order of fastest access speed?

  1. Auxiliary storage, then main memory, then cache memory, then registers
  2. Registers, then cache memory, then main memory, then auxiliary storage
  3. Main memory, then cache memory, then registers, then auxiliary storage
  4. Cache memory, then registers, then main memory, then auxiliary storage
AnswerB. Registers, then cache memory, then main memory, then auxiliary storage

The memory hierarchy runs, from the top, registers, cache memory, main memory, and auxiliary storage, with higher levels faster, smaller, and more expensive. The first option reverses registers and cache, the third wrongly puts main memory at the top, and the fourth lists them in order of slowest speed.

Q13 | Effective access time

When the cache memory access time is 10 nanoseconds, the main memory access time is 100 nanoseconds, and the cache hit rate is 0.9, what is the effective access time in nanoseconds?

  1. 100
  2. 10
  3. 55
  4. 19
AnswerD. 19

The effective access time is found by weighting the hit and miss times by their probabilities: 0.9×10 + 0.1×100 = 9 + 10 = 19 nanoseconds. 10 is the value at a 100% hit rate, 55 is the simple average, and 100 is the value with no cache; all of these ignore the weighting principle.

Q14 | Main vs auxiliary

Which of the following is an appropriate comparison of main memory and auxiliary storage?

  1. Main memory is faster than auxiliary storage, but its price per unit of capacity is higher
  2. Main memory is slower than auxiliary storage but has larger capacity
  3. Auxiliary storage loses its contents when the power is turned off, so it is unsuitable for long-term storage
  4. Auxiliary storage is read and written directly by the CPU and is therefore faster than main memory
AnswerA. Main memory is faster than auxiliary storage, but its price per unit of capacity is higher

Main memory is fast because the CPU reads and writes it directly, but its price per capacity is higher than auxiliary storage and its capacity smaller. The first option reverses the speed-capacity relationship. It is main memory that the CPU accesses directly, so the second is wrong, and auxiliary storage is non-volatile and retains contents with the power off, so the fourth is wrong too.

Q15 | USB

Which of the following is an appropriate characteristic of USB?

  1. It is a wireless standard that communicates when brought within a few centimeters
  2. It is a dedicated standard that transmits only video and audio
  3. The computer must be powered off every time a device is connected
  4. It can connect many kinds of peripheral devices and can also supply power to them
AnswerD. It can connect many kinds of peripheral devices and can also supply power to them

USB can connect a wide variety of devices such as keyboards, printers, and external SSDs, and also supports powering devices through the cable, bus power. The first option describes HDMI and the third NFC. USB supports hot plugging, connecting and disconnecting with the power on, so the fourth is also wrong.

Q16 | HDMI

Which standard connects a PC and a display with a single cable, transmitting video and audio together as digital signals?

  1. HDMI
  2. Bluetooth
  3. IEEE1394
  4. NFC
AnswerA. HDMI

HDMI is a standard that digitally transmits video and audio over a single cable and is used for connecting displays and televisions. Bluetooth is short-range wireless over a few meters and NFC is near-field wireless over a few centimeters; both are wireless standards. IEEE1394 is a fast wired interface, but it is not the standard for sending combined video and audio to display devices.

Q17 | NFC

Which standard, communicating at a distance of a few centimeters, is used when passing through a ticket gate by holding up a transit IC card?

  1. NFC
  2. HDMI
  3. IEEE1394
  4. USB
AnswerA. NFC

NFC is a wireless standard that communicates only at very close range and is used for IC card tickets, electronic money, and tap payments. USB, HDMI, and IEEE1394 are all wired interfaces connected by cable and cannot communicate by holding a device near a reader.

Q18 | Bluetooth

Which of the following is an appropriate statement about Bluetooth?

  1. It is a standard that can communicate only when devices are brought within a few centimeters
  2. It is a standard that uses power lines as the communication path to transmit data within the home
  3. It is a standard for wirelessly connecting mice, earphones, and the like at distances of a few meters
  4. It is a standard that communicates over tens of kilometers using optical fiber
AnswerC. It is a standard for wirelessly connecting mice, earphones, and the like at distances of a few meters

Bluetooth is a short-range wireless standard that connects devices within a range of a few meters and is used for mice, keyboards, earphones, and the like. The first option describes optical fiber communication, the second NFC, and the fourth power line communication, PLC; none of these is Bluetooth.

Q19 | Device drivers

Which of the following is an appropriate role of a device driver?

  1. It mediates between the OS and a peripheral device and controls that device
  2. It translates source code into machine language, producing an executable form
  3. It allocates CPU time among multiple programs
  4. It encrypts communications on the network to prevent eavesdropping
AnswerA. It mediates between the OS and a peripheral device and controls that device

A device driver is control software prepared for each peripheral device, bridging the OS and the device. The second option is the OS's task management, the third an encryption mechanism, and the fourth the work of a compiler; each is a role separate from controlling peripherals.

Q20 | Actuators

Which of the following appropriately describes an actuator in an IoT system?

  1. A storage device that keeps large amounts of data for long periods
  2. A communication component that sends collected data to the cloud over the Internet
  3. A component that receives electrical signals and drives motors, valves, and the like, acting on its target
  4. A component that measures conditions such as temperature and brightness and converts them into electrical signals
AnswerC. A component that receives electrical signals and drives motors, valves, and the like, acting on its target

An actuator is a component that converts electrical signals into physical motion, serving as the outlet that acts on the real world. The first option describes a sensor, which is the inlet that captures information from the real world. The second is a communication module and the third a storage device; neither is an actuator.

Q21 | OLED

In what respect is an OLED display superior to a liquid crystal display?

  1. It can output documents and charts at the same quality as printed on paper
  2. The displayed content remains on the screen even after the power is turned off
  3. The screen can be operated by touching it directly with a finger
  4. The pixels themselves emit light, so no backlight is needed and the display can be made thin
AnswerD. The pixels themselves emit light, so no backlight is needed and the display can be made thin

OLED is a method in which the pixels themselves emit light; no rear backlight is needed, making thin designs easy, and deep blacks can be rendered by leaving pixels unlit. The first option is a touch panel function, separate from the display method. The third is about printers, and the fourth is a characteristic of electronic paper that does not apply to OLED.

Q22 | Embedded systems

Which of the following is the most appropriate example of an embedded system?

  1. A general-purpose server to which users can freely add applications
  2. An office PC that tallies sales with spreadsheet software
  3. A computer built into a rice cooker that controls only the heating time and temperature
  4. A business database management system used by every department in the company
AnswerC. A computer built into a rice cooker that controls only the heating time and temperature

An embedded system is a computer system built into a device that performs only a specific function, and a rice cooker's controller is a classic example. The other three are all general-purpose computer systems that perform a variety of processing without restricting the use, so they do not count as embedded systems.

Q23 | Client-server

Which of the following appropriately describes a client-server system?

  1. A technology that runs multiple virtual computers on a single computer
  2. A configuration in which all participating computers exchange data directly on an equal footing
  3. A technology that combines multiple magnetic disks to act as one
  4. A configuration that divides roles between computers that provide services and computers that use them
AnswerD. A configuration that divides roles between computers that provide services and computers that use them

A client-server system is a configuration that divides roles between servers, which provide services, and clients, which use them. The second option describes peer-to-peer, the third virtualization, and the fourth RAID; none of them is about dividing roles.

Q24 | Thin clients

What is the main advantage of introducing thin clients?

  1. The terminal's own processing power increases, allowing heavy computation such as video editing locally
  2. Even if the server fails and stops, work can continue on the terminal alone
  3. Because no data is stored on the terminal, information leaks from terminal loss or theft are easier to prevent
  4. Even with the network disconnected, work can continue as is on the local terminal alone
AnswerC. Because no data is stored on the terminal, information leaks from terminal loss or theft are easier to prevent

Thin clients concentrate processing and data on the server side and leave no data on the terminal, lowering the risk of information leaks when a terminal is lost or stolen. Terminal-side processing becomes lighter, so the first option is wrong, and since processing depends on the server, work cannot continue when the server or network is unavailable, as in the second and fourth options.

Q25 | Virtualization

Which of the following is an appropriate benefit gained by introducing server virtualization?

  1. Physical servers can be consolidated, reducing floor space and power consumption
  2. The processing capacity of a single server physically increases
  3. Network communication speed becomes faster than the line's upper limit
  4. Data is guaranteed never to be lost even when server hardware fails
AnswerA. Physical servers can be consolidated, reducing floor space and power consumption

Virtualization is a technology that runs multiple virtual servers on one physical server, and consolidation reduces floor space, power, and management effort. Physical processing capacity does not increase, so the first option is wrong; failure protection needs separate mechanisms such as backups and RAID, so the second is wrong; and the fourth is unrelated to communications technology.

Q26 | Peer-to-peer

Which of the following is an appropriate characteristic of the peer-to-peer model?

  1. Terminals only display the screen, and all processing is done on the server
  2. All processing is concentrated on a single large computer
  3. Servers and disks are connected by a fast network dedicated to storage
  4. Without a central server, each computer exchanges data directly on an equal footing
AnswerD. Without a central server, each computer exchanges data directly on an equal footing

Peer-to-peer is a model in which the participating computers communicate directly as equals. The second option is a centralized processing system, the third thin clients or VDI, and the fourth a SAN; none is a configuration of direct exchange between equals.

Q27 | NAS and SAN

Which of the following appropriately describes NAS?

  1. A mechanism that runs a virtual desktop environment for each user on a server
  2. A configuration that links multiple computers to work as one, raising processing power
  3. A storage device connected directly to the network that lets multiple computers share files
  4. A mechanism that pools the idle time of many computers to perform one large computation
AnswerC. A storage device connected directly to the network that lets multiple computers share files

NAS is a storage device dedicated to file sharing that is used connected directly to the network, and it is easy to deploy. The first option is grid computing, the second VDI, and the third a cluster. A separate high-speed network dedicated to storage is a SAN, which is distinguished from NAS.

Q28 | Edge computing

Which of the following appropriately describes edge computing?

  1. Sending all data to the cloud as is, with both processing and storage done only in the cloud
  2. Cutting power to unused equipment to hold down power consumption
  3. Splitting one computation and assigning the pieces to computers around the world
  4. Placing processing devices near users and equipment, processing there, and sending only the necessary data to the cloud
AnswerD. Placing processing devices near users and equipment, processing there, and sending only the necessary data to the cloud

Edge computing processes data near the site where it is generated and sends only what is needed to the center, the cloud, reducing traffic and shortening response times. The first option is conventional cloud use without the edge, the third is grid computing, and the fourth describes a power-saving measure.

Q29 | RAID 1

Which of the following appropriately describes RAID 1, mirroring?

  1. The same data is written to 2 disks, so operation can continue even if one fails
  2. Data and parity are recorded spread across 3 or more disks
  3. Data is spread across multiple disks and written simultaneously to raise speed
  4. The disk's contents are periodically copied to another medium and stored
AnswerA. The same data is written to 2 disks, so operation can continue even if one fails

RAID 1 writes the same content to 2 disks, so if one fails, processing continues on the other, though usable capacity is half of the total. The first option is RAID 0 and the second RAID 5. The fourth describes backup, which differs from RAID 1's constant duplicate writing in both purpose and mechanism.

Q30 | RAID comparison

Which of the following statements about RAID 0, RAID 1, and RAID 5 is appropriate?

  1. With RAID 1, the usable capacity equals the total capacity of the connected disks
  2. With RAID 0, data can be restored from the remaining disks even if one fails
  3. RAID 5 uses no parity, so its reads and writes are faster than RAID 0
  4. RAID 5 requires 3 or more disks and can restore data after a single disk failure
AnswerD. RAID 5 requires 3 or more disks and can restore data after a single disk failure

RAID 5 records data and parity spread across 3 or more disks, and if one fails, the data can be restored from the rest. RAID 0 has no redundancy and loses data on a single failure, so the first option is wrong; RAID 1 writes everything twice, so usable capacity is half and the second is wrong; and RAID 5 does use parity, so the fourth is wrong.

Q31 | Clusters

Which configuration connects multiple computers at high speed so the whole behaves like a single computer, raising processing power and availability?

  1. Peer-to-peer
  2. Thin client
  3. Cluster
  4. Edge computing
AnswerC. Cluster

A cluster is a configuration that links multiple computers to operate as one, aiming at higher performance through shared processing and higher availability by continuing processing even when one machine stops. Thin clients lighten the terminal, peer-to-peer is a form of communication between equals, and edge computing processes at the site; none of these applies.

Q32 | Dual vs duplex

Which of the following appropriately explains the difference between a dual system and a duplex system?

  1. A dual system is divided into primary and secondary, while a duplex system always runs two sets simultaneously
  2. Both run two sets simultaneously, but only the dual system does not cross-check the results
  3. A dual system is a technology for duplicating disks, while a duplex system is a technology for duplicating CPUs
  4. A dual system always runs two sets simultaneously and cross-checks the results, while a duplex system processes on the primary and keeps the secondary on standby
AnswerD. A dual system always runs two sets simultaneously and cross-checks the results, while a duplex system processes on the primary and keeps the secondary on standby

A dual system always runs two identically configured sets in parallel and processes while matching their results against each other. A duplex system runs production on the primary and keeps the secondary waiting, switching over on failure. The second option swaps the two descriptions, the third reverses the cross-checking, and the fourth confuses the matter with RAID, so all are wrong.

Q33 | Cold standby

Which of the following appropriately describes cold standby in a duplex system?

  1. The failed part is isolated and processing continues even at reduced functionality
  2. The same processing is performed on both the primary and the standby, and the results are cross-checked
  3. The standby system is also powered on with the same system running, so switching happens quickly when the primary fails
  4. The standby system is kept stopped and is started and switched to when the primary fails, so costs are low but switching takes time
AnswerD. The standby system is kept stopped and is started and switched to when the primary fails, so costs are low but switching takes time

Cold standby keeps the standby system stopped; costs stay low, but startup and switchover take time. The second option describes hot standby, where the standby is kept powered on. The third is a dual system and the fourth fail-soft; none of these is cold standby.

Q34 | Foolproofing

Which of the following is an example of design based on the foolproof concept?

  1. A washing machine will not start running while its lid is open
  2. When a traffic signal fails, it displays red to stop the cars
  3. Some functions are stopped so that the service continues even at reduced performance
  4. Two servers are prepared so that processing continues even if one fails
AnswerA. A washing machine will not start running while its lid is open

Foolproofing is design that keeps mistaken operation by users from leading to danger or breakdown, and a washing machine that will not run with the lid open is an example. The first option is fail-safe, the second fault tolerance, redundancy through duplication, and the third fail-soft; all of those address failures rather than guarding against operating errors.

Q35 | Fail-soft

Which response is based on the fail-soft concept?

  1. When some servers fail, stopping their functions and continuing processing on the remaining servers
  2. An oil heater that automatically extinguishes itself when knocked over
  3. Making an input field accept only digits so that invalid values cannot be entered
  4. Making equipment redundant so that the whole keeps running without losing functionality even when parts fail
AnswerA. When some servers fail, stopping their functions and continuing processing on the remaining servers

Fail-soft is the idea of isolating the failed part and keeping the system running even at reduced functionality or performance. The first option is foolproofing, the second fail-safe, and the fourth fault tolerance. The difference from the fourth is that fail-soft tolerates degraded functionality, whereas fault tolerance aims to maintain full normal functionality.

Q36 | Availability (series)

What is the availability of a system in which device A with availability 0.9 and device B with availability 0.8 are connected in series? Assume the devices' failures do not affect each other.

  1. 0.98
  2. 0.80
  3. 0.85
  4. 0.72
AnswerD. 0.72

A series connection is usable only when every device is working, so the overall availability is the product of the individual values: 0.9×0.8 = 0.72. 0.98 is the parallel calculation 1−(1−0.9)×(1−0.8), 0.85 is the average of the two, and 0.80 is the value of the weaker device; none of these is the series calculation.

Q37 | Availability (parallel)

Two devices, each with availability 0.9, are connected in parallel so that the system is usable as long as either one is working. What is the availability of this system? Assume the devices' failures do not affect each other.

  1. 1.80
  2. 0.99
  3. 0.81
  4. 0.90
AnswerB. 0.99

For a parallel connection, subtract from 1 the probability that both stop at the same time: 1−(1−0.9)×(1−0.9) = 1−0.01 = 0.99. 0.81 is the series calculation 0.9×0.9, 0.90 is the value for a single device, and 1.80 simply adds the availabilities, which is wrong since availability can never exceed 1.

Q38 | MTBF and availability

What is the availability of a system whose MTBF is 475 hours and whose MTTR is 25 hours?

  1. 0.90
  2. 0.95
  3. 0.98
  4. 0.05
AnswerB. 0.95

Availability is MTBF ÷ (MTBF + MTTR), so 475÷(475+25) = 475÷500 = 0.95. 0.05 is MTTR ÷ (MTBF + MTTR), which represents the fraction of time the system is down for failures. 0.98 and 0.90 result from neither formula.

Q39 | Availability (3 in series)

What is the availability of a system in which 3 devices, each with availability 0.9, are connected in series? Assume the devices' failures do not affect each other.

  1. 0.729
  2. 0.900
  3. 0.999
  4. 0.810
AnswerA. 0.729

The availability of a series connection is the product of the devices' values, so 0.9×0.9×0.9 = 0.729. 0.810 is the value for 2 devices in series, 0.900 is for a single device, and 0.999 is the parallel calculation 1−(1−0.9)^3 for 3 devices; none is the value for 3 in series.

Q40 | Fail-safe

When a railroad crossing gate fails, it stays lowered; when a traffic signal fails, it displays red. Which reliability design concept do these have in common?

  1. Fail-safe
  2. Foolproof
  3. Fail-soft
  4. Fault tolerant
AnswerA. Fail-safe

Fail-safe is design that, when a failure occurs, tips things toward the safe side so that no accident results, and the crossing gate and signal examples fit this. Foolproofing guards against users' operating mistakes, fail-soft isolates the failed part and continues processing even at reduced functionality, and fault tolerance preserves overall functionality through redundancy; none of those aims at tipping toward the safe side.

Q41 | Availability (combined)

Device A with availability 0.9 is connected in series with a block consisting of devices B and C, each with availability 0.9, connected in parallel. What is the availability of this system? Assume the devices' failures do not affect each other.

  1. 0.891
  2. 0.729
  3. 0.990
  4. 0.810
AnswerA. 0.891

First treat the parallel block as one device: its availability is 1−(1−0.9)×(1−0.9) = 0.99. Connecting this in series with device A gives 0.9×0.99 = 0.891. 0.729 treats all 3 as a series, 0.810 is 2 in series, and 0.990 is the parallel block alone; none accounts for the series connection with device A.

Q42 | Computing MTBF

A system was operated for 1000 hours, during which 5 failures occurred and repairs took a total of 50 hours. Which combination of MTBF and MTTR is correct? Here the 1000 hours represent operating time without failures.

  1. MTBF = 200 hours, MTTR = 10 hours
  2. MTBF = 200 hours, MTTR = 50 hours
  3. MTBF = 5 hours, MTTR = 50 hours
  4. MTBF = 1000 hours, MTTR = 10 hours
AnswerA. MTBF = 200 hours, MTTR = 10 hours

MTBF is total operating time divided by the number of failures, 1000÷5 = 200 hours, and MTTR is total repair time divided by the number of failures, 50÷5 = 10 hours. The first option swaps the two. The third does not divide the repair time by the count, and the fourth does not divide the operating time by the failure count, so both are wrong. The availability here would be 200÷(200+10), about 0.952.

Q43 | Performance metrics

Which of the following appropriately describes an indicator of system performance or cost?

  1. Throughput is the amount of work that can be processed per unit of time
  2. Response time is the time from requesting processing until all results have been received
  3. A benchmark is the fraction of time a system is in a usable state
  4. TCO is the total of only the initial costs incurred when introducing a system
AnswerA. Throughput is the amount of work that can be processed per unit of time

Throughput is the amount of work processed in a given time; the larger it is, the higher the processing capacity. The first option describes turnaround time, whereas response time is the time until the first response starts coming back. TCO is the sum of initial and operating costs, so the third is wrong, and a benchmark is a method of measuring and comparing performance with programs under identical conditions, so the fourth is wrong too; the fraction of usable time is availability.

Q44 | Copying references 3

Cell D2 of a spreadsheet contains "=B2/$B$10". When this formula is copied to cell D5, which formula appears in D5?

  1. =B5/$B$10
  2. =B5/$B$13
  3. =B2/$B$10
  4. =E5/$E$10
AnswerA. =B5/$B$10

Copying from D2 to D5 keeps the column the same and shifts the row by 3. The relative reference B2 shifts 3 rows to become B5, while the absolute reference $B$10 has both column and row fixed and does not change. Hence "=B5/$B$10". The first option fails to shift the relative reference, the second shifts even the absolute reference, and the fourth shifts the column as well, so they are wrong.

Q45 | Role of the OS

Which of the following is an appropriate role of the OS, the basic software?

  1. Translating source code into machine language, producing an executable form
  2. Managing resources such as the CPU and main memory, providing the foundation on which applications run
  3. Performing the user's actual tasks themselves, such as spreadsheets and word processing
  4. Receiving the content of Web pages and displaying it on screen
AnswerB. Managing resources such as the CPU and main memory, providing the foundation on which applications run

The OS manages hardware resources and provides the foundation on which applications run, through task management, memory management, file management, and input/output management. The first and second options are the work of application software, spreadsheets and Web browsers, and the third is the work of a compiler; none is the OS's proper role.

Q46 | Relative paths

Directly under the root directory is dirA; directly under dirA are dirB and dirC; and directly under dirC is file.txt. When the current directory is dirB, which of the following specifies file.txt with a relative path? Here the directory separator is "/", the current directory is ".", and the parent directory is "..".

  1. ../../dirC/file.txt
  2. ../dirC/file.txt
  3. ./dirC/file.txt
  4. /dirC/file.txt
AnswerB. ../dirC/file.txt

Seen from the current directory dirB, dirC sits directly under the parent, dirA. So the correct path first goes up with ".." to dirA, then enters dirC to reach file.txt: "../dirC/file.txt". The second option would be the way to write it if dirC were under dirB, the third is the absolute-path form starting from the root, and the fourth goes all the way back to the root, where there is no dirC directly underneath, so it is wrong.

Q47 | OSS

Which of the following is an appropriate statement about OSS, open source software?

  1. The author has renounced the copyright, so it can be handled freely without regard to usage conditions
  2. It is limited to personal use, and companies cannot use it in their business
  3. It is always provided free of charge, and selling it for a fee is not permitted
  4. The source code is published, and improvement and redistribution are allowed under the conditions the license sets
AnswerD. The source code is published, and improvement and redistribution are allowed under the conditions the license sets

OSS is software whose source code is published and which can be used, improved, and redistributed under the conditions its license sets. The copyright is not renounced, so the first option is wrong; being free of charge is not a condition and paid distribution is possible, so the third is wrong; and business use by companies is also possible if the conditions are observed, so the fourth is wrong.

Q48 | File formats

Which text-only file format lays out tabular data one record per line, with the fields separated by commas? It is often used for passing data between different software products.

  1. ZIP
  2. MP4
  3. CSV
  4. PDF
AnswerC. CSV

CSV is a text-only format with fields separated by commas, making data easy to pass even between different software products. PDF is a document format for displaying and printing with the same appearance across environments, ZIP is a format for bundling and compressing multiple files, and MP4 is a video format; none is for exchanging tabular data.

Q49 | Copying references 1

Cell B2 of a spreadsheet contains "=A1*$C$1". When this formula is copied to cell C3, which formula appears in C3?

  1. =B2*$C$1
  2. =A1*$C$1
  3. =B2*$D$2
  4. =A1*$D$2
AnswerA. =B2*$C$1

Copying from B2 to C3 shifts one column and one row. The relative reference A1 shifts by the same amount to become B2, and the absolute reference $C$1 has both its column and row fixed by the $ signs, so it does not change. Hence "=B2*$C$1". The second option fails to shift the relative reference, and the third and fourth shift even the absolute reference, so they are wrong.

Q50 | Copying references 2

Cell C3 of a spreadsheet contains "=$A3+B$1". When this formula is copied to cell E5, which formula appears in E5?

  1. =$C5+D$3
  2. =$A5+D$1
  3. =$A3+B$1
  4. =$A5+B$5
AnswerB. =$A5+D$1

Copying from C3 to E5 shifts 2 columns and 2 rows. In $A3 the column A is fixed and only the row shifts, giving $A5; in B$1 the row 1 is fixed and only the column shifts, giving D$1. Hence "=$A5+D$1". The first option shifts nothing. The third shifts the fixed column A, and the fourth shifts the fixed row 1, so they are wrong.

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