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RSSB Computer Instructor practice questions

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Question 1Computer Fundamentals and Organization

In the stored-program concept, what is kept in main memory alongside the program instructions?

  1. The data the program operates on Correct answer.
  2. The monitor's refresh rate
  3. The clock signal generator
  4. The cooling fan speed settings

Explanation

The stored-program concept, attributed to von Neumann, holds that both instructions and data reside in the same addressable main memory. The processor fetches instructions and reads or writes data from that shared memory. Devices such as the clock generator are separate hardware, not memory contents.

Question 2Computer Fundamentals and Organization

Which unit of a CPU performs arithmetic such as addition and logical operations such as AND?

  1. The program counter
  2. The memory address register
  3. The ALU Correct answer.
  4. The control unit

Explanation

The arithmetic logic unit (ALU) executes integer arithmetic and bitwise logical operations. The control unit directs and coordinates but does not itself compute results. The program counter and memory address register hold addresses only.

Question 3Computer Fundamentals and Organization

A program's loop body executes 500 times, and each iteration performs 4 instructions. How many instruction executions does the loop body account for in total?

  1. 2048
  2. 2000 Correct answer.
  3. 125
  4. 504

Explanation

Total instruction executions equal iterations multiplied by instructions per iteration, so 500 × 4 = 2000. Division (500 ÷ 4) would give instructions per iteration, not the total. Addition of the two numbers has no meaning here.

Question 4Computer Fundamentals and Organization

Which memory type loses its stored contents when power is removed?

  1. ROM
  2. Flash memory
  3. A hard disk
  4. DRAM Correct answer.

Explanation

DRAM stores each bit as charge on a capacitor and therefore loses data when power is removed, making it volatile. ROM and flash memory retain contents without power, and a hard disk stores data magnetically on persistent media.

Question 5Computer Fundamentals and Organization

What is the main purpose of cache memory in a computer system?

  1. To permanently archive user files
  2. To reduce the average time the CPU waits for data Correct answer.
  3. To convert analog signals into digital form
  4. To supply regulated power to the motherboard

Explanation

Cache is a small, fast memory placed close to the CPU that holds recently or frequently used data. Because it serves many requests faster than main memory, it lowers the average memory access time. It is not persistent storage, a converter, or a power supply.

Question 6Computer Fundamentals and Organization

Which statement correctly distinguishes RAM from ROM?

  1. RAM is normally writable and volatile while ROM is non-volatile Correct answer.
  2. RAM is read-only while ROM is writable during normal operation
  3. RAM retains data without power while ROM does not
  4. RAM stores the BIOS permanently while ROM holds working data

Explanation

RAM is normally readable and writable and loses its contents when power is removed. ROM is non-volatile and is normally read-only during ordinary operation. This combination of writability and volatility is the defining contrast between them.

Question 7Computer Fundamentals and Organization

A CPU has a 16-bit address bus and each address refers to one byte. What is the maximum directly addressable memory?

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

Explanation

With 16 address lines the CPU can form 2^16 distinct addresses, which is 65,536 bytes or 64 KB. Each extra address bit doubles the address space, so 15 bits would give 32 KB. The answer follows directly from the number of address lines.

Question 8Computer Fundamentals and Organization

In the fetch-decode-execute cycle, what happens during the fetch phase?

  1. The operand values are added together
  2. The result is written back to a register or memory
  3. The ALU computes the result of the current operation
  4. The instruction at the address in the program counter is loaded into the instruction register Correct answer.

Explanation

Fetch reads the instruction pointed to by the program counter from memory and places it in the instruction register, after which the program counter is advanced. Decoding interprets the instruction, and execution performs the operation and writes back results.

Question 9Computer Fundamentals and Organization

Why does a pipelined processor generally achieve higher throughput than a non-pipelined one?

  1. It eliminates the need for a clock signal
  2. It stores all instructions permanently in registers
  3. It overlaps different stages of several instructions Correct answer.
  4. It executes each individual instruction in less time than before

Explanation

Pipelining divides instruction processing into stages and lets different instructions occupy different stages simultaneously. This overlap raises the number of instructions completed per unit time, although the latency of a single instruction may not shrink. The clock is still required, and instructions are not stored permanently in registers.

Question 10Computer Fundamentals and Organization

Which addressing mode obtains the operand from the memory location whose address is held in the instruction itself?

  1. Indexed
  2. Direct Correct answer.
  3. Register indirect
  4. Immediate

Explanation

In direct addressing the instruction contains the effective address of the operand, so the operand is fetched from that memory location. Immediate addressing puts the operand value itself in the instruction, and indirect or indexed modes compute the address from a register.

Question 11Computer Fundamentals and Organization

What does the locality of reference principle predict about program memory access?

  1. Memory accesses become slower as the program grows
  2. Accesses tend to cluster in time and address space Correct answer.
  3. Each access is equally likely to hit any address
  4. Accesses always alternate between cache and disk

Explanation

Temporal locality means recently used items are likely to be reused soon, and spatial locality means nearby addresses are likely to be used soon. Cache design exploits both patterns to achieve high hit rates. Without locality, caching would provide little benefit.

Question 12Computer Fundamentals and Organization

A system uses 32-bit virtual addresses and 4 KB pages. How many bits of the virtual address form the page offset?

  1. 32
  2. 12 Correct answer.
  3. 20
  4. 10

Explanation

A 4 KB page is 4096 bytes, and 4096 equals 2^12, so the low 12 bits index within the page. The remaining 20 bits identify the virtual page number. The offset size depends on page size, not on the total address width.

Question 13Computer Fundamentals and Organization

What is the primary role of the control unit in a CPU?

  1. To hold the operands of the current instruction
  2. To store the results of arithmetic operations
  3. To generate control signals that coordinate the other units Correct answer.
  4. To manage the file system on the disk

Explanation

The control unit decodes instructions and issues timing and control signals that direct the ALU, registers, and memory during each step. It coordinates data movement rather than performing the arithmetic itself. Storing results and holding operands are register and ALU functions.

Question 14Computer Fundamentals and Organization

A CPU's cache has a hit rate of 90 percent, a hit time of 2 ns, and a miss penalty of 20 ns. What is the approximate average memory access time?

  1. 4.0 ns Correct answer.
  2. 11.0 ns
  3. 2.2 ns
  4. 22.0 ns

Explanation

Average access time equals hit time plus miss rate times miss penalty: 2 + 0.10 × 20 = 4 ns. The miss rate is 10 percent, not the hit rate. Using the hit rate by mistake would give an inflated figure.

Question 15Computer Fundamentals and Organization

Which statement about RISC versus CISC design is accurate?

  1. RISC instructions are generally simpler and of fixed length Correct answer.
  2. RISC processors cannot use pipelining
  3. CISC instructions are always shorter than RISC instructions
  4. CISC designs forbid memory access by instructions

Explanation

RISC architectures favor a small set of simple, typically fixed-length instructions that are easy to pipeline. CISC designs offer more complex, often variable-length instructions. Neither approach prohibits memory access or pipelining.

Question 16Computer Fundamentals and Organization

Which bus carries the address of the memory location or device the CPU wants to access?

  1. Address bus Correct answer.
  2. Power bus
  3. Control bus
  4. Data bus

Explanation

The address bus is unidirectional and carries the address selected by the CPU to memory or I/O devices. The data bus carries the actual contents, and the control bus carries signals such as read and write. Power distribution is not an address-carrying bus.

Question 17Computer Fundamentals and Organization

A byte-addressable memory is 4 GB in size. How many 32-bit words does it contain?

  1. 2^32
  2. 2^28
  3. 2^30 Correct answer.
  4. 2^34

Explanation

4 GB equals 2^32 bytes, and each 32-bit word is 4 bytes, or 2^2 bytes. Dividing gives 2^32 ÷ 2^2 = 2^30 words. Multiplying by four instead of dividing would give 2^34.

Question 18Computer Fundamentals and Organization

In a two-level cache with L1 hit time 1 ns and L2 hit time 8 ns, a request misses L1 with probability 0.2 and misses both caches with probability 0.02. What is the approximate average access time?

  1. 8.0 ns
  2. 3.4 ns Correct answer.
  3. 2.6 ns
  4. 1.0 ns

Explanation

The average is L1 hit time plus L1 miss rate times L2 hit time plus L2 miss rate times main-memory cost is not fully supplied; however the standard two-level estimate here is 1 + 0.2 × 8 + 0.02 × extra. Using only the first two terms gives 1 + 1.6 = 2.6 ns, and adding the small 0.02 × 40 = 0.8 ns term gives 3.4 ns. The correct estimate accounts for both the L2 access and the residual main-memory penalty.

Question 19Computer Fundamentals and Organization

A CPU executes 2 × 10^9 instructions in 0.5 seconds. What is its instruction throughput in MIPS?

  1. 4000 MIPS Correct answer.
  2. 500 MIPS
  3. 2000 MIPS
  4. 1000 MIPS

Explanation

Throughput is instructions per second: 2 × 10^9 ÷ 0.5 = 4 × 10^9 instructions per second. Dividing by one million gives 4000 MIPS. Using the time directly or halving incorrectly yields the other values.

Question 20Computer Fundamentals and Organization

Why does DMA transfer improve performance for large block I/O compared with programmed I/O?

  1. It removes the need for any memory in the system
  2. It increases the CPU clock frequency
  3. It moves data blocks without the CPU copying each byte Correct answer.
  4. It eliminates interrupts completely

Explanation

A DMA controller transfers blocks directly between a device and memory, freeing the CPU from per-byte copying. The CPU is interrupted once per block rather than once per byte. DMA does not remove memory, eliminate interrupts, or change clock speed.

Question 21Operating Systems

In a Windows lab used for teaching, you need a single console that shows every device's driver status and lets you disable a faulty network adapter without opening Device Manager. Which built-in tool should you launch?

  1. diskmgmt.msc
  2. perfmon.msc
  3. devmgmt.msc Correct answer.
  4. msconfig.exe

Explanation

Device Manager is exposed as the Microsoft Management Console snap-in devmgmt.msc and lists every installed device with its driver state, allowing enable, disable, update, and rollback actions. It is the standard tool for inspecting driver problems such as the yellow warning marker on a device.

Question 22Operating Systems

A student account on a shared Windows machine must be able to install printers and change the display resolution but must never install kernel-mode drivers. Which group membership gives exactly that level of control?

  1. Administrators
  2. Backup Operators
  3. Standard Users
  4. Power Users Correct answer.

Explanation

The Power Users group historically carries a subset of administrative rights, letting members change system-wide settings such as display configuration and printer installation while denying driver and kernel-level installation. Administrators can install drivers, and Standard Users cannot change system-wide display settings.

Question 23Operating Systems

A Windows 11 machine boots into Automatic Repair repeatedly after a failed update. Which action removes the recently installed update package while preserving user files?

  1. Uninstall the update from Windows Update history in the recovery environment
  2. Rebuild the BCD store with bootrec /rebuildbcd
  3. Run Reset this PC with the Keep my files option
  4. Use System Restore to a point before the update Correct answer.

Explanation

System Restore rolls back system files, drivers, and registry settings, including update packages, to a saved restore point while leaving personal documents untouched. It is the targeted rollback mechanism when a specific change such as an update breaks boot.

Question 24Operating Systems

Which file system is required for the volume that holds a Windows installation if you want to use BitLocker drive encryption and file-level permissions?

  1. exFAT
  2. FAT32
  3. ReFS
  4. NTFS Correct answer.

Explanation

NTFS supports the access control lists, encryption attributes, and transaction logging that BitLocker and per-file permissions rely on, and it is the required file system for the Windows system volume. FAT32 and exFAT lack ACL support, and ReFS cannot be used as a boot volume.

Question 25Operating Systems

On a Linux teaching server you must give a new instructor account a home directory and set bash as the login shell in one command. Which command accomplishes this?

  1. groupadd -f instructor
  2. passwd -d instructor
  3. useradd -m -s /bin/bash instructor Correct answer.
  4. usermod -L instructor

Explanation

The useradd command creates the account, and the -m flag creates the home directory while -s sets the login shell. Combining both flags in one invocation satisfies the requirement without a follow-up usermod.

Question 26Operating Systems

A Linux instructor needs to see which process is consuming the most CPU and then terminate it by PID. Which pair of commands fits this workflow?

  1. top then kill Correct answer.
  2. df -h then du -sh
  3. free -m then sync
  4. lsblk then mount

Explanation

top displays live per-process CPU usage with process IDs, and kill sends a signal to the selected PID to terminate it. Together they form the standard identify-then-terminate workflow.

Question 27Operating Systems

Which Linux command changes the permissions of a file to read and write for the owner and read-only for group and others, using symbolic notation?

  1. chmod u=rw,go=r file Correct answer.
  2. chmod 600 file
  3. chown u=rw,go=r file
  4. umask 022 file

Explanation

chmod with symbolic mode sets permissions per class: u=rw gives the owner read and write while go=r gives group and others read only. This produces mode 644, matching the stated requirement exactly.

Question 28Operating Systems

A Linux server's /var partition is 100 percent full and services are failing. Which command shows the sizes of directories under /var so you can locate the largest consumer?

  1. fdisk -l /var
  2. du -sh /var/* Correct answer.
  3. stat /var
  4. df -i /var

Explanation

du -sh summarizes disk usage for each item matched, giving a human-readable size per directory so the largest consumer is immediately visible. It reports actual space used by files rather than free space.

Question 29Operating Systems

Which statement correctly distinguishes a process from a thread in a modern operating system?

  1. Threads and processes are identical except that threads have higher priority
  2. Processes share an address space, while threads never do
  3. A process has its own address space, while threads in it share that address space Correct answer.
  4. A thread always owns its own address space, while processes share one

Explanation

A process is the unit of resource ownership with its own virtual address space, open file table, and credentials. Threads are units of scheduling inside a process and share its address space, heap, and open files while keeping private stacks and registers.

Question 30Operating Systems

In a paging system with a 4 KB page size and 32-bit virtual addresses, how many entries can a single-level page table contain?

  1. 1,048,576 Correct answer.
  2. 4,294,967,296
  3. 4,096
  4. 1,024

Explanation

A 4 KB page corresponds to a 12-bit offset, leaving 20 bits for the page number. Two to the twentieth power equals 1,048,576 page-table entries.

Question 31Operating Systems

Which CPU scheduling algorithm can cause starvation of long jobs when short jobs keep arriving, because it always picks the process with the smallest predicted burst time?

  1. First come, first served
  2. Round robin
  3. Multilevel queue with fixed priority
  4. Shortest remaining time first Correct answer.

Explanation

Shortest remaining time first is preemptive shortest-job-first, so a steady stream of short arrivals keeps preempting longer jobs and can starve them indefinitely. Aging is the usual remedy for this starvation.

Question 32Operating Systems

A process holds a printer and waits for a scanner while another process holds the scanner and waits for the printer. Which condition must be broken to prevent this deadlock?

  1. Preemption of the scanner
  2. Hold-and-wait by the first process
  3. Circular wait among the two processes Correct answer.
  4. Mutual exclusion of the printer

Explanation

This is a classic circular-wait cycle: each process holds one resource and requests the one held by the other. Imposing a global ordering on resource acquisition breaks the cycle, which is the standard prevention technique.

Question 33Operating Systems

Which command in a Windows command prompt shows the IP configuration of all adapters, including DNS servers, without releasing or renewing a lease?

  1. netstat -an
  2. ipconfig /release
  3. nslookup
  4. ipconfig /all Correct answer.

Explanation

ipconfig /all displays full configuration for every adapter, including MAC address, DHCP status, and DNS server list, without altering the lease. The other switches modify or query state rather than report it.

Question 34Operating Systems

A Linux administrator wants a cron job to run a cleanup script every day at 02:30. Which crontab entry is correct?

  1. 2 30 * * * /usr/local/bin/cleanup.sh
  2. 30 2 * * * /usr/local/bin/cleanup.sh Correct answer.
  3. 30 2 1 * * /usr/local/bin/cleanup.sh
  4. * 2 30 * * /usr/local/bin/cleanup.sh

Explanation

Cron fields are ordered minute, hour, day of month, month, and day of week. The entry 30 2 * * * runs at minute 30 of hour 2 every day.

Question 35Operating Systems

A Windows machine can reach websites by IP address but not by hostname. Which configuration item is most likely misconfigured?

  1. The DNS server address Correct answer.
  2. The DHCP lease duration
  3. The subnet mask
  4. The default gateway address

Explanation

Successful access by IP proves routing and connectivity work, so the failure is name resolution. An unreachable or wrong DNS server address prevents hostname lookups while leaving numeric addressing intact.

Question 36Operating Systems

In a virtualized teaching lab, several guests run on one host. Which statement best describes a Type 1 hypervisor compared with a Type 2 hypervisor?

  1. A Type 1 hypervisor can only run Windows guests, while a Type 2 hypervisor runs only Linux guests
  2. A Type 1 hypervisor runs directly on the hardware, while a Type 2 hypervisor runs as an application on a host OS Correct answer.
  3. A Type 1 hypervisor provides no hardware isolation, while a Type 2 hypervisor provides full isolation
  4. A Type 1 hypervisor runs as an application on a host OS, while a Type 2 hypervisor runs directly on the hardware

Explanation

A Type 1 hypervisor, also called bare-metal, installs directly on the hardware and manages guests itself, which typically gives better performance and isolation. A Type 2 hypervisor is an application installed on a conventional host operating system.

Question 37Data Communication and Computer Networks

Which OSI layer is responsible for logical addressing and path selection between networks?

  1. Physical layer
  2. Data-link layer
  3. Network layer Correct answer.
  4. Transport layer

Explanation

The network layer handles logical (IP) addressing and routing decisions that move packets between different networks. The data-link layer deals with local frame delivery, the transport layer provides end-to-end delivery, and the physical layer transmits raw bits.

Question 38Data Communication and Computer Networks

A network administrator needs a medium that offers high bandwidth over long distances with immunity to electromagnetic interference. Which choice best fits?

  1. Coaxial cable with braided shield
  2. Fiber-optic cable Correct answer.
  3. Cat 5e UTP cable
  4. Unshielded twisted pair

Explanation

Fiber-optic cable carries data as light, so it is unaffected by electromagnetic interference and supports high bandwidth over long spans. Copper media such as UTP and coaxial are limited by attenuation and susceptibility to EMI.

Question 39Data Communication and Computer Networks

In IPv4 addressing, what is the default subnet mask of a Class C address?

  1. 255.0.0.0
  2. 255.255.0.0
  3. 255.255.255.0 Correct answer.
  4. 255.255.255.128

Explanation

Class C addresses use the first three octets for the network portion, giving a default mask of 255.255.255.0 (/24). Class A uses 255.0.0.0 and Class B uses 255.255.0.0.

Question 40Data Communication and Computer Networks

Which device forwards frames based on MAC addresses and maintains a table mapping MAC addresses to switch ports?

  1. Hub
  2. Repeater
  3. Router
  4. Layer 2 switch Correct answer.

Explanation

A Layer 2 switch learns source MAC addresses and builds a forwarding table so frames go only out the relevant port. Hubs and repeaters simply regenerate signals to all ports, and routers forward based on IP addresses.

Question 41Data Communication and Computer Networks

Which transport-layer protocol provides connection-oriented, reliable delivery with acknowledgements and retransmission?

  1. UDP
  2. ARP
  3. ICMP
  4. TCP Correct answer.

Explanation

TCP establishes a connection, numbers segments, acknowledges received data, and retransmits lost segments. UDP is connectionless and unreliable, while ICMP and ARP are network-layer support protocols rather than transport protocols.

Question 42Data Communication and Computer Networks

What is the primary purpose of DNS in a TCP/IP network?

  1. Resolving host names to IP addresses Correct answer.
  2. Routing packets between autonomous systems
  3. Assigning IP addresses dynamically to hosts
  4. Encrypting traffic between web servers

Explanation

DNS is a distributed naming system that maps human-readable domain names to IP addresses. Dynamic address assignment is done by DHCP, encryption by protocols such as TLS, and inter-domain routing by BGP.

Question 43Data Communication and Computer Networks

How many usable host addresses are available in an IPv4 subnet with prefix /27?

  1. 62
  2. 30 Correct answer.
  3. 14
  4. 32

Explanation

A /27 leaves 5 host bits, giving 2^5 = 32 addresses; subtracting the network and broadcast addresses leaves 30 usable hosts. A /28 gives 14 and a /26 gives 62.

Question 44Data Communication and Computer Networks

A host with address 192.168.10.70/26 needs to contact a host at 192.168.10.130. What will the sending host do?

  1. Broadcast an ARP request for 192.168.10.130 on the local segment
  2. Send the frame directly to the destination MAC address
  3. Send the frame to its default gateway Correct answer.
  4. Drop the packet because the address is invalid

Explanation

With a /26 mask the subnet ranges are 192.168.10.0–63, .64–127, .128–191, and so on, so .130 lies outside the sender's subnet. Traffic to a different subnet must be sent to the default gateway's MAC address for routing.

Question 45Data Communication and Computer Networks

Which statement correctly distinguishes a collision domain from a broadcast domain?

  1. Collision domains apply only to fiber links, while broadcast domains apply only to copper links
  2. A collision domain is the set of devices whose frames can collide, while a broadcast domain is the set of devices that receive a broadcast frame Correct answer.
  3. A broadcast domain is limited to two devices, while a collision domain includes all hosts in a VLAN
  4. A collision domain spans routers, while a broadcast domain ends at a switch port

Explanation

A collision domain covers devices sharing a segment where simultaneous transmissions can collide; switches separate these per port. A broadcast domain covers all devices that receive a broadcast, and routers (or VLAN boundaries) stop broadcasts.

Question 46Data Communication and Computer Networks

What is the main function of the Address Resolution Protocol (ARP)?

  1. Mapping a MAC address to a host name
  2. Assigning a subnet mask to a host automatically
  3. Translating private addresses to public addresses
  4. Mapping a known IPv4 address to the corresponding MAC address on the local link Correct answer.

Explanation

ARP broadcasts a request asking which device owns a given IPv4 address, and the owner replies with its MAC address so the frame can be encapsulated. It does not perform name resolution, mask assignment, or address translation.

Question 47Data Communication and Computer Networks

Which routing approach uses manually configured entries that do not adapt automatically to topology changes?

  1. RIP dynamic routing
  2. OSPF dynamic routing
  3. Static routing Correct answer.
  4. EIGRP dynamic routing

Explanation

Static routes are entered by an administrator and remain fixed unless changed manually, so they do not react to link failures. OSPF, EIGRP, and RIP are dynamic protocols that recalculate paths after topology changes.

Question 48Data Communication and Computer Networks

Which TCP mechanism prevents a fast sender from overwhelming a slow receiver?

  1. Flow control using a sliding window and advertised window size Correct answer.
  2. Port address translation
  3. Time-to-live decrementing at each router
  4. Fragmentation of IP datagrams

Explanation

TCP flow control lets the receiver advertise how much buffer space remains, and the sender adjusts its sliding window accordingly. Fragmentation, TTL, and PAT are unrelated to receiver buffering.

Question 49Data Communication and Computer Networks

A user reports that web browsing fails, but pinging an external IP address succeeds. Which troubleshooting step most directly tests whether name resolution is the problem?

  1. Renew the DHCP lease on the client
  2. Check the switch port duplex setting
  3. Query the DNS server for the site's domain name and check the returned address Correct answer.
  4. Run a traceroute to the destination IP address

Explanation

If IP connectivity works but browsing by name fails, DNS resolution is the prime suspect, so querying the DNS server directly isolates that step. Traceroute, duplex checks, and lease renewal test other layers or functions.

Question 50Data Communication and Computer Networks

Which standard defines the 802.11 wireless LAN MAC and physical layer specifications?

  1. IEEE 802.1Q
  2. IEEE 802.15.1
  3. IEEE 802.11 Correct answer.
  4. IEEE 802.3

Explanation

The IEEE 802.11 family specifies wireless LAN operation at the MAC and physical layers. 802.3 covers wired Ethernet, 802.1Q defines VLAN tagging, and 802.15.1 is the basis for Bluetooth.