AR101 MIDTERM

Module 6-9

• Non-volatile auxiliary storage that provides high-capacity, cost-effective data retention for computer systems.

• Significantly slower than main memory (RAM) and processor registers, requiring specialized management techniques.

• Primary technologies include magnetic disks, RAID arrays, optical storage media, and magnetic tapes.

External Memory

• Constructed from a circular platter made of a nonmagnetic substrate (traditionally aluminum alloy, now increasingly glass).

• Coated with a thin magnetizable material on one or both sides to retain binary data permanently.

• Glass substrates improve surface uniformity, lower fly heights for read/write heads, and enhance shock resistance.

Magnetic Disk

Data is recorded and retrieved via a conductive electromagnetic component called a _, which stays stationary while the platter spins underneath.

head

utilizes electric current pulses flowing through a coil to induce a magnetic field, polarizing small areas of the medium.

write mechanism

exploits electromagnetic induction, where moving magnetic patterns generate a corresponding electrical current in the coil.

read mechanism

Data is organized into concentric rings called _, which are further divided into smaller manageable chunks called - separated by -.

tracks, sectors, gaps

Systems use _ to optimize data density across varying track radiuses.

Constant Angular Velocity (CAV) or Multiple Zone Recording (MZR)

• Developed to bridge the massive performance gap between fast modern processors and slower mechanical hard drives.

• Combines multiple physical hard disks into a single logical unit managed by the operating system.

• Relies on core architectural mechanisms: data striping (for speed) and redundancy/parity (for fault tolerance).

RAID Technology

Distributes data blocks evenly across disks for maximum performance, but offers zero redundancy—if one drive fails, all data is lost.

RAID 0 (Stripping)

• Duplicates identical data onto twin disks, ensuring high read performance and instant failover protection.

• Carries a 100% storage overhead cost since every gigabyte saved requires a matching duplicate gigabyte.

RAID 1 (Mirroring)

Utilizes low-power laser technology to read microscopic physical indentations ("pits") and flat areas ("lands") stamped onto a polycarbonate disc.

Optical Memory

Operates with a standard infrared/red laser operating at wider track spacing and lower overall data densities.

CD-ROM / CD-R / CD-RW

uses an organic dye layer that is permanently altered by a writing laser, while CD-RW uses a phase-change metallic alloy for rewritable capability.

CD-R

Employs a shorter wavelength red laser (650nm), allowing tighter track spacing and capacities starting at 4.7GB.

DVD

Switches to a much shorter wavelength blue- violet laser (405nm), drastically shrinking the pit size and beam width.

achieves capacities of 25GB on a single layer and up to 50GB(or more) on dual-layer formats.

Blu-ray

• Controls the execution of application programs and system software.

• Acts as an intermediary interface between user applications and computer hardware.

• Manages system resources like CPU time, memory, storage, and input/output devices.

Operating Systems

Primary Objectives of an Operating System

• Convenience: Makes the computer hardware easier and more intuitive for users and programmers to utilize.

• Efficiency: Allows computer system resources (CPU, RAM, I/O) to be operated in an optimal, high-throughput manner.

• Ability to Evolve: Permits effective development, testing, and introduction of new system functions without disrupting service.

When one job needs to wait for slow I/O operations, the CPU switches to execute another ready program.

Multiprogrammed Batch Systems

Uses multiprogramming to handle multiple interactive users simultaneously via rapid task- switching.

Time-Sharing Systems

Periodic hardware timer interrupts prevent a single runaway program from monopolizing the CPU indefinitely.

Timer Interrupts

Signals sent to the CPU by external devices (like keyboards or disks) to alert it that an event requires immediate attention.

Hardware Interrupts

A program in execution, serving as the fundamental unit of work managed by the operating system.

Process

The low-level mechanism that rapidly selects which ready process executes next in the CPU time slot.

Short - Term Scheduling (Dispatcher)

Five State Model

New
Ready

Running

Blocked/Waiting

Exit

Determines which new programs are admitted into the system queue, controlling the overall degree of multiprogramming.

Long-Term Scheduling

Manages the system swapping function, moving suspended processes back and forth between RAM and disk.

Medium-Term Scheduling

A specialized OS data structure containing critical metadata like Process ID, register states, and priorities.

Process Control Block (PCB)

Temporarily moving entire inactive processes out of main memory into secondary storage (disk) to clear space for active ones.

Swapping

The OS maintains tracking tables to know which physical memory addresses are allocated and which are free.

Memory Tracking

Main memory is divided into static, predefined partitions; suffers from internal fragmentation (wasted space inside blocks).

Fixed Partitioning

Partitions are created variably to fit exact process sizes as they arrive in the system.

Dynamic Partitioning

Allows execution of programs even when they are only partially loaded into main memory.

Virtual Memory

Divides physical memory into fixed blocks called frames and programs into equal-sized blocks called pages, mapped via page tables.

Paging

Divides memory into variable-length logical blocks (like code, data, stack) reflecting the programmer's view.

Segmentation

A computer receives information from a keyboard and sends processed information to a monitor. What general computer function makes these exchanges possible?

Input/Output

A computer connects a printer to its internal system. Which component serves as the communication link between the printer and the computer's processor and memory?

I/O Module

A temperature-monitoring system uses a sensor to detect changes in the surrounding environment and convert them into electrical signals. What device component performs this conversion?

Transducer

A computer uses a device that converts electrical signals into information that can be understood by a person. Which category of external device is being described?

Human-readable device

A computer technician connects a modem to allow data exchange between computers over a communication network. What type of peripheral is the modem?

Communication Device

A processor communicates with peripherals that operate at different speeds. Which I/O module function helps prevent the processor from being directly affected by these speed differences?

Buffering

A computer repeatedly checks a printer's status before sending another portion of data. Which I/O transfer technique is being used?

Programmed I/O

A processor sends an instruction to an external device and continues performing other tasks while waiting for the device to become ready. Which technique is demonstrated?

Interrupt-Driven I/O

A storage device needs to transfer a large block of information into main memory without requiring the CPU to handle every individual data unit. Which technique is most appropriate?

Direct Memory Access

During an interrupt-driven transfer, what event informs the processor that an external device needs attention?

interrupt signal

A processor spends too much time repeatedly checking whether an I/O device is ready. What is the main disadvantage of this situation?

it wastes processor time

A DMA controller needs to move a block of information from an external storage device into RAM. Which resource must the controller take control of to perform this transfer?

System Bus

After a DMA controller completes a block transfer, what is the main benefit to the processor?

It can avoid handling every individual unit of the completed transfer.

A large multimedia system requires an I/O subsystem that can independently manage complex sequences of data transfers. Which component is designed for this purpose?

I/O Processor

A company needs a high-speed connection for transferring large multimedia files between external devices. Which interface is identified in Module 8 as a high-speed serial standard?

Firewire

A server cluster requires a high-throughput connection for communication and data exchange. Which high-speed interface discussed in Module 8 is suitable for this type of application?

InfiniBand

A computer's I/O module temporarily holds data while transferring information between devices that operate at different speeds. What is this process called?

Buffering

A student uses a keyboard to enter one character into a computer. Which I/O method is appropriate for a simple input operation where the CPU can check the device's status?

Programmed I/O

A computer must transfer a very large video file from an external SSD to main memory. Which method is best suited to reduce repeated CPU involvement during the transfer?

Direct Memory Access

A computer system uses an I/O module to coordinate the exchange of information between the system bus and a peripheral's control logic. Which I/O module function is being emphasized?

Control and timing

Which component serves as the intermediary between the CPU or memory and external peripheral devices?

I/O Module

Which I/O transfer technique requires the CPU to repeatedly check the device's status until it is ready?

Programmed I/O

Which technique uses a specialized controller to transfer blocks of data directly between an I/O device and main memory?

Direct Memory Access

Which external device component converts physical energy into electrical signals or electrical signals into physical energy?

Transducer

Which dedicated component can manage complex data-transfer operations using its own specialized instructions?

I/O Processor

A processor receives two numerical values and performs addition before sending the result to another component. Which processor component performs this operation?

Arithmetic Logic Unit

A computer compares two binary values to determine whether they are equal. Which type of operation is being performed by the ALU?

Logical Operation

After completing an arithmetic operation, the processor records information indicating whether the result is zero or whether an overflow occurred. What are these indicators called?

Status Flags

A processor receives two operands from its internal registers before performing an arithmetic calculation. What role do these operands serve?

They provide the data that the ALU processes

A programmer represents a negative integer by using the most significant bit to indicate the sign and the remaining bits to represent its magnitude. Which representation method is being used?

Sign - Magnitude

A computer system needs to represent signed integers without having separate positive-zero and negative-zero representations. Which method should it use?

Two’s Complement

A student is asked to find the negative equivalent of a binary number using two's complement. Which procedure should be followed?

Complement every bit and then add 1.

A processor expands a signed binary value from a smaller bit-width to a larger bit-width while preserving its numerical value. Which technique is used?

Sign Extension

A fixed-width processor produces an arithmetic result that cannot be represented within the available number of bits. What condition has occurred?

Overflow

A computer performs subtraction using two's complement arithmetic. Which operation allows subtraction to be handled through addition?

Adding the negated subtrahend to the minuend

A multiplication operation uses repeated shifting and addition to calculate the product of two binary numbers. What arithmetic process is being described?

Multiplication

A processor performs binary division and produces two values: one representing the result of the division and another representing what remains. What are these values called?

Quotient and remainder

A scientific application needs to represent very large and very small real numbers using a sign, a significand, and an exponent. Which representation approach is appropriate?

Scientific Notation

A computer system stores floating-point values using a standard that defines a 32-bit single-precision format.  

A graphics application requires the 64-bit double-precision floating-point format for numerical calculations.

Which standard is being used?

IEEE 754

Before adding two floating-point numbers, a processor aligns their exponents by adjusting the significands so that the values can be combined properly. What step is being performed

Exponent Alignment

After performing a floating-point calculation, a processor adjusts the significand and exponent to place the result into the required standard form. What operation is this?

Normalization

A floating-point calculation produces a special value indicating that the result is not a valid numerical value. Which IEEE 754 special value represents this condition?

NaN (Not-a-Number)

A processor adjusts a floating-point result to fit within the precision supported by its storage format. Which operation is being performed?

Rounding

Which processor component performs arithmetic calculations and logical comparisons based on signals from the control unit?

ALU

Which signed integer representation uses the most significant bit as a sign indicator and the remaining bits for magnitude?

Sign Magnitude Representation

Which signed integer representation performs negation by complementing each bit and adding 1?

Two's Complement Representation

Which standard defines single-precision and double-precision binary floating-point formats?

IEEE 754

Which special floating-point value indicates that a result is not a valid numerical number?

NaN (Not-a-Number)