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← Unit 2: Hardware, Software and Operating Systems

TEJ3M · Unit 2 test review

Hardware, Software and Operating Systems: Test Review

Everything for the Unit 2 test on one page: the key facts from all 5 lessons, the mistakes that cost the most marks, and a practice test that points you back to the lessons you need.

Key facts

The CPU and the Motherboard

  • The machine cycle is fetch → decode → execute → store, repeated billions of times per second.
  • Inside a core: control unit (directs), ALU (calculates), registers (hold the current values).
  • The program counter holds the address of the NEXT instruction.
  • Three buses: address (where), data (what), control (read or write, and when).
  • A 32-bit address bus can address bytes = 4 GiB — the historical 32-bit RAM ceiling.
  • Clock speed only compares fairly within one CPU generation; cores, cache and IPC matter as much.

Memory and Storage

  • The hierarchy runs registers → L1 → L2 → L3 → RAM → SSD → HDD, getting slower and larger each step.
  • Everything above the SSD line is volatile.
  • RAM is read-write and volatile; ROM is non-volatile and holds firmware.
  • Virtual memory uses drive space as overflow for RAM — it prevents crashes but is about 1000× slower.
  • SSDs beat HDDs most dramatically on random access, not on sequential throughput.
  • RAID provides availability, not backup.

Building a System and Connecting Peripherals

  • Drain residual power by unplugging and holding the power button for five seconds before opening a case.
  • A chip can be destroyed by a static charge of about 30 V — far below the ~3000 V you can feel.
  • PSU rails: +12 V (CPU and GPU, the main load), +5 V and +3.3 V for logic and drives.
  • Size a PSU with roughly 30% headroom above the measured system draw.
  • USB-C is a connector shape, not a speed standard.
  • Hot-swappable: USB, Ethernet, SATA. Never hot-swap: RAM, CPU, PCIe cards.
  • Motherboard standoffs prevent the board shorting against the case.

Firmware, POST and the Boot Sequence

  • POST runs before any operating system exists, and reports failures by beeps or LEDs because the display may not work yet.
  • Firmware hands control to the bootloader, which loads the kernel into RAM; firmware's job then ends.
  • UEFI replaced legacy BIOS: GPT partitioning, drives over 2 TiB, 128 partitions, and Secure Boot.
  • Legacy BIOS + MBR is limited to 2 TiB drives and four primary partitions.
  • A dead CMOS battery causes forgotten settings and a wrong clock, not a dead machine.
  • Changing SATA mode after installing Windows causes a boot failure, because the storage driver no longer matches.

Operating Systems, File Systems and Maintenance

  • The OS manages processes, memory, files, devices and security.
  • On a single core, multitasking is rapid switching, not simultaneous execution.
  • FAT32 caps a single file at about 4 GB; exFAT and NTFS do not.
  • Deleting a file removes its directory entry and frees its blocks — the data stays until overwritten.
  • Never defragment an SSD: it gains nothing and burns write cycles.
  • 3-2-1 backups: three copies, two media types, one off-site — and test a restore.

Where marks get lost

  • Ranking CPUs by clock speed across different generations — IPC improvements make that comparison meaningless. (The CPU and the Motherboard)
  • Saying the ALU decodes instructions. The control unit decodes; the ALU only calculates. (The CPU and the Motherboard)
  • Thinking cache is a type of RAM slot you can upgrade. Cache is fabricated inside the CPU and is fixed. (The CPU and the Motherboard)
  • Assuming a CPU works in any board with the same socket. The chipset and firmware version matter too. (The CPU and the Motherboard)
  • Confusing cores with threads. Four cores with hyper-threading present eight threads, but there are still only four sets of execution hardware. (The CPU and the Motherboard)
  • Calling RAM "memory" and storage "memory" in the same sentence without distinguishing them. (Memory and Storage)
  • Thinking adding RAM makes the CPU faster. It removes a bottleneck; it does not raise the clock. (Memory and Storage)
  • Believing virtual memory is a substitute for RAM. It prevents out-of-memory crashes at an enormous speed cost. (Memory and Storage)
  • Treating RAID 1 as a backup. It copies deletions and ransomware just as faithfully as it copies real data. (Memory and Storage)
  • Assuming cache can be upgraded. It is fabricated inside the CPU die and is fixed at manufacture. (Memory and Storage)
  • Forgetting the 8-pin EPS CPU power connector — the fans spin, so the machine looks alive while never posting. (Building a System and Connecting Peripherals)
  • Not pressing RAM until both clips click. Partially seated RAM produces no display and no beep. (Building a System and Connecting Peripherals)
  • Handling cards and modules by their gold contacts instead of their edges. (Building a System and Connecting Peripherals)
  • Mounting a motherboard without standoffs, or leaving an extra standoff under an area with no screw hole, which shorts the board. (Building a System and Connecting Peripherals)
  • Opening a power supply to "check" it. Its capacitors hold a lethal charge long after it is unplugged. (Building a System and Connecting Peripherals)
  • Applying far too much thermal paste. A pea-sized dot spreads correctly under cooler pressure; excess insulates instead of conducting. (Building a System and Connecting Peripherals)
  • Saying the operating system runs POST. POST happens before any OS is loaded — that is the whole point of firmware. (Firmware, POST and the Boot Sequence)
  • Thinking a dead CMOS battery prevents booting. It causes forgotten settings and a wrong clock; the machine still starts. (Firmware, POST and the Boot Sequence)
  • Using "BIOS" and "UEFI" as if they were the same thing in an exam answer that asks you to compare them. (Firmware, POST and the Boot Sequence)
  • Changing SATA mode from AHCI to RAID after Windows is installed, then being surprised by a boot failure. (Firmware, POST and the Boot Sequence)
  • Updating firmware for no reason. The upside is usually zero and the downside is a dead motherboard. (Firmware, POST and the Boot Sequence)
  • Defragmenting an SSD — no benefit, real wear cost. (Operating Systems, File Systems and Maintenance)
  • Believing a deleted file is gone. The blocks are marked free but the data stays until overwritten. (Operating Systems, File Systems and Maintenance)
  • Assuming a USB stick with free space can hold any file. FAT32 caps single files at 4 GB. (Operating Systems, File Systems and Maintenance)
  • Calling a copy on the same drive a backup. A drive failure destroys both the original and the copy. (Operating Systems, File Systems and Maintenance)
  • Trusting a backup that has never been restored from. (Operating Systems, File Systems and Maintenance)
  • Thinking a single-core CPU runs programs genuinely simultaneously. The scheduler switches between them very fast. (Operating Systems, File Systems and Maintenance)

Practice test

25 questions from across the unit. Each one shows the lesson it comes from.

  1. The CPU and the Motherboard
    1
    Which register holds the address of the next instruction to be fetched?
  2. The CPU and the Motherboard
    2
    A 3.6 GHz core completes one instruction per cycle. How many instructions does it execute in 2 milliseconds? Give your answer in millions.
    million
  3. The CPU and the Motherboard
    3
    A motherboard's address bus is 40 bits wide. How much memory can it address?
  4. The CPU and the Motherboard
    4
    A student installs 16 GB of RAM as one single module in a dual-channel board. What is the consequence?
  5. The CPU and the Motherboard
    5
    Which upgrade would most help a program that runs as a single thread and constantly re-reads a small 2 MB table?
  6. Memory and Storage
    6
    Which of these is NOT volatile?
  7. Memory and Storage
    7
    Order these from fastest access time to slowest.
    1. 1L2 cache
    2. 2Hard disk drive
    3. 3Main memory (DRAM)
    4. 4CPU register
  8. Memory and Storage
    8
    Why does an SSD have a limited lifespan that a hard drive does not share?
  9. Memory and Storage
    9
    If an L1 cache access takes 1 ns and a RAM access takes 60 ns, how many times slower is RAM?
  10. Memory and Storage
    10
    A business keeps its only copy of customer records on a RAID 1 array. What risk remains?
  11. Building a System and Connecting Peripherals
    11
    A new build has spinning fans and lit LEDs but no display and no beep. What should you check first?
  12. Building a System and Connecting Peripherals
    12
    Why is a wrist strap clipped to the chassis rather than just working carefully?
  13. Building a System and Connecting Peripherals
    13
    Which of these can safely be connected while the computer is running?
  14. Building a System and Connecting Peripherals
    14
    Put these assembly steps in a sensible order.
    1. 1Attach the cooler with thermal paste
    2. 2Mount the board on standoffs and connect the 24-pin and 8-pin cables
    3. 3Install RAM in the slots the manual specifies
    4. 4Fit the CPU into the socket on the bench
  15. Building a System and Connecting Peripherals
    15
    Match each connector to what it powers.
    24-pin ATX
    8-pin EPS
    6/8-pin PCIe
    SATA power
  16. Firmware, POST and the Boot Sequence
    16
    Put these boot stages in order.
    1. 1POST checks CPU, RAM and video
    2. 2The kernel loads drivers and mounts the file system
    3. 3Firmware finds a boot device and loads the bootloader
    4. 4PSU sends the Power Good signal
  17. Firmware, POST and the Boot Sequence
    17
    Which is an advantage of UEFI over legacy BIOS?
  18. Firmware, POST and the Boot Sequence
    18
    Why does POST report errors with beeps rather than an on-screen message?
  19. Firmware, POST and the Boot Sequence
    19
    A technician changes SATA mode from AHCI to RAID in firmware on a working Windows machine. What happens next?
  20. Firmware, POST and the Boot Sequence
    20
    During which stage does the computer FIRST have an operating system running?
  21. Operating Systems, File Systems and Maintenance
    21
    A 6 GB file will not copy to a USB stick with 40 GB free. The most likely cause is:
  22. Operating Systems, File Systems and Maintenance
    22
    What is the OS component that decides which process gets CPU time next?
  23. Operating Systems, File Systems and Maintenance
    23
    Order these layers from closest to the hardware to closest to the user.
    1. 1Device drivers
    2. 2Application software
    3. 3Operating system kernel
    4. 4Hardware
  24. Operating Systems, File Systems and Maintenance
    24
    Match each file system to its defining characteristic.
    NTFS
    exFAT
    FAT32
    ext4
  25. Operating Systems, File Systems and Maintenance
    25
    A file system uses 4 KB blocks. How many blocks does a 10 000 byte file occupy? (Blocks cannot be shared between files.)
    blocks

Endless drill

Fresh numbers every time, for the calculation questions in this unit.

Endless drillnew numbers every time

Generating a problem…

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