Computer Input, Process, Output Model

Unit 4: Computer

Input, Process, Output Model

• A computer is a machine utilizing given inputs from its surroundings and processes the information using rules and regulations that yield an output.
• Processing involves applying a series of actions to the inputs based on a defined set of rules.
• For processing to generate meaningful results, it must follow an algorithm.
• An algorithm can be defined as a precise method that solves a problem using step-by-step instructions.
• The computer depends on an algorithm that leads to an output.
• The algorithm requires temporary storage or memory for the computer to keep track of the output.

Range of Computational Models

• Computational models describe how algorithms are executed.
• There are various computational models available.

Sequential Model

• Computer executes instructions step-by-step.
• For example, to execute (2+3) * (10/5) + (4-1) the CPU would first calculate (2+3) = 5, then (10/5) = 2, then (4-1) = 3, then 5*2 = 10, and finally 10 + 3 = 13.

Parallel Model

• Processes are distributed between two or more installed processors.
• Each algorithm part can be combined together.
• Requires an operating system that supports two or more processors.
• Software program capable of distributing processes between processors equally is required.
• Example for the equation (2+3) * (10/5) + (4-1), CPU 1 calculates (2+3) = 5 and (4-1) = 3, while CPU 2 calculates (10/5) = 2, then 5*2 = 10 before being combined.

Multi-Agent Model

• Separate tasks or algorithms are processed by different agents to perform a particular function.
• Each agent is autonomous, cooperating through negotiation and coordination.

Hardware

Store Programs: The Von Neumann Model

• Von Neumann computers process data using a stored program concept.
• Instructions and data are stored in the main memory.
• CPU runs a program by accessing the main memory.
• Fetch-decode-execute cycle is used to run programs.

CPU: Hardware Component of a Computer

• An electronic circuit that executes instructions using the fetch-decode-execute cycle.
• Also known as a processor or microprocessor.
• CPU consists of the CU, ALU, Clock, Register, and Cache.

Arithmetic Logic Unit (ALU)

• The ALU performs calculations and logical operations.

Control Unit (CU)

• The CU is the part of the CPU that controls the flow of data and the interaction between different parts of the CPU.

Clock

• Produces timing signals on the control bus.
• The vital synchronization ensures the computer doesn't crash.

Register

• A storage area inside the CPU holds an instruction, address, or data.
• Memory Address Register (MAR) stores the memory location's address currently being read or written to.
• Memory Data Register (MDR) stores data being stored or retrieved from memory.
• Accumulator (ACC) holds results of calculations performed by the ALU.
• Accumulator passes all inputs and outputs from the CPU.
• Program Counter (PC) holds the memory address of the next instruction to be fetched.
• Current Instruction Register (CIR) holds the instruction currently being executed.

Bus

• Connects the CPU to other devices.

Address Bus

• Unidirectional.
• Carries memory addresses between the CPU and Memory or Input/output devices.

Data Bus

• Bidirectional.
• The bus carries data values to be read from or written to memory or Input/output devices.

Control Bus

• Bidirectional.
• The bus carries the control signals from the CU to other computer components.

Bus width

• The number of wires makes up a bus.
• Bus width determines the range of binary numbers that can be communicated.
• Increasing the number of data bus wires will increase the data transmission rate and the number of bits that can be transferred.
• Increasing the number of address bus wires can increase the amount of memory locations addressed.

Fetch - Decode - Execute Cycle

• By the stored program concept, data and instructions are stored in the same memory as RAM.
• To execute a set of instructions, the processor first fetches the data, storing in registers.
• Each instruction must be decoded before executing
• Together, these steps are the fetch-decode-execute cycle.

Fetch

• The CU places the memory address of the next instruction on the address bus.
• The CU sends the read control signal to get a request to read from memory.
• The memory receives the signal and looks up the memory address.
• Data in the memory is copied on to the data bus.
• The CPU copies this data into a CIR.

Decode

• The CU decodes the contents of the CIR.
• The CU sends the signal to other CPU parts that tell them what to do.

Execute

• The CPU completes the instruction.

Input Device

• Any hardware devices that send data and commands to interact and control a computer.
• The input devices include scanners, digital cameras, microphones, interactive whiteboards, barcode readers, keyboards, touchscreens, QR code readers, mice, and sensors.

Output Device

• It shows the results of computer processing in a human-understandable form.
• Examples include printers, monitors, loudspeakers and projectors.

Component of Von Neumann Model

• The model has the following components: clock, input device, central processing unit, control unit, arithmetic/logic Unit, register, cache memory, main memory (RAM), and output device.

Factors that Affect CPU Performance

Clock Speed

• Clock speed controls the rate at which instructions are processed by the CPU.
• The greater the clock speed, the faster the rate of processing.
• The clock speed of CPU 3GHZ (3 billion instructions per second) is common in modern computers.
• Increasing clock speed to increase processing speed has disadvantages.
• With increased clock speed, the processors generate heat. A fan and heat sink help get rid of that heat to prevent melting.
• Processor with clock speeds of 9 GHz needs to be cooled by liquid nitrogen.

Number of Processor Cores

• Multi-core processors have more than one processor, increasing processor speed.
• With a multicore processor working on the same program, the processing is called parallel processing, or multitasking with different programs at the same time.
• Not all programs run with twice the speed of dual-core processor.

Size of Cache

• The speed of processing is limited by RAM, which supplies the instructions regardless of clock speed or cores.
• In a fetch- execute cycle, RAM slower than the CPU causes bottleneck. Using faster memory known as cache within the CPU is the solution to the bottleneck.
• A cache's data is used to store frequently used data.
• The CPU can check the fast cache for the data needed.
• The CPU does not have to wait for the data to be fetched from main memory.
• Larger cache means cached instructions or data and RAM can be accessed faster.
• Static RAM or SRAM is used for cache.

Primary Memory

• Accessed directly by the CPU.

Random Access Memory (RAM)

• Contents are temporary; can be written to, read from, or be erased.
• It is volatile and its contents are lost when power is switched off.
• Operating systems, running programs, and processing data are primarily held in RAM.
• RAM capacity can range from a few bytes to GBs, depending on the device.

Read-Only Memory (ROM)

• Only readable with permanent contents.
• It is non-volatile, thus, retaining its contents when power is switched off.
• ROM stores firmware (BIOS) and bootstraps.
• ROM tends to be of a much smaller capacity than RAM.

Cache Memory

• A small amount of fast, and expensive memory.
• Used to speed up communication between devices communicating at different speeds like the CPU and RAM.
• Frequently used code or data in a CPU cache gets loaded in chunks from the slower RAM into the cache.
• CPU accesses cache memory faster than it would RAM.
• The CPU is not slowed down since it does not have to wait for RAM data.

Virtual Memory

• RAM can be full due to an operating system and several applications running simultaneously.
• A memory manager in the OS uses virtual memory to store some data on the hard disk drive instead of closing program.
• A process that is running on the computer may need to store data in the physical memory (RAM).
• If memory is not free, the memory manager swaps out the least recently used data stored in RAM to the swap area on the hard disk drive.
• The memory manager will then swap in any new data requested into the free area.

Advantages of using virtual memory:

• Programs can be larger than the physical memory (RAM) available.
• The need to install and buy more expensive RAM memory decreased.

Disadvantages of using virtual memory:

• There could be a significant drop in performance if the system relies too heavily on virtual memory.
• The read/write speed of a hard drive being much slower than that of RAM.
• OS has to swap information back and forth, operating all of the time, causing disk thrashing,.

Secondary Storage

• Needed for storage of data and programs when power is off, data change, and backup of data files.
• The three types are: magnetic, solid-state, and optical storage.
• The secondary storage is non-volatile; RAM/ROM contents are copied.

Magnetic Secondary Storage

• Used in hard disk drives and magnetic tapes.
• The magnets, north poles (N-S) and south poles (S-N) can represent the 1s and 0s of data.

Data Storage

• Data is stored on the magnetic surfaces of the disk as it writes.
• Each disk writes along circular tracks, creating sectors.
• While the disk spins, a read/write head moves across its surface.
• To write data, the disk magnetizes a section spinning.

When data is read:

• The arm moves to be above the right track.
• The right sector is available under the head.
• The surface behaves like a magnet, creating a small current in the head.
• The disk controller translates the 1 and 0.

Advantages of Magnetic Secondary Storage

• Cheaper cost per data unit.
• Fast read and write speeds.
• Reliable technology.
• Commonly used in desktop computers, laptop computer, servers, and mainframes.

Drawbacks of Magnetic Secondary Storage

• Nature of moving parts means they will wear down and break.
• Never performs as fast as solid state drives as they wait for the parts to move.
• More fragile and less robust than solid state drives.
• Higher power consumption than a SSD.
• Some noise is created by the moving parts.

Solid-state storage

• Chips called NAND flash that are made of transistor that retain charges.

SSD data storage:

• NAND flash consists of transistors being placed in rows and columns.
• Row and column intersections contain transistors called control gates and floating gates.
• Floating gate transistors have values of 1 when charged and values of 0 when uncharged.
• Precise voltages applied to the transistors makes a unique pattern of 1s and 0s emerge.

Advantages of Solid-state Storage

• Fast read/write speeds.
• Small and light.
• Little wear, damage, or fail, making them more reliable and durable.

Drawbacks of Solid-state Storage

• High costs (per GB).
• Limited capacity.
• Limited writes.
• Common applications of Solid-state storage include:
  • Smartphones
  • Tablet computers
  • High-end laptops
  • Two drive desktop solutions
  • Portable drives in video cameras

Optical Secondary Storage

• CDs and DVDs are used.
• Data is written along a single track from the center of the disc.
• Each player uses 2 laser beams, one to write, and one to read.
• Microscopic data pits and lands form these storage.
• Disc rotates/spins, using a laser to R/W data.
• Data is written in a spiral/concentric track pattern.
• Lasers will indent, creating pits and bumps along a surface.
• The pits and lands are binary values of 0 and 1.

The data tracks the laser into the correct position over the disc.

• The laser shines onto this disc, which reflects back into a light sensor.
• Sensor signals translate into 1 and 0.

Advantages of optical secondary storage:

• Low cost per data.
• Light weight.
• Easily transportable.
• Best durability

Drawbacks of optical secondary storage:

• Some traditional PCs cannot read these discs.

Optical storage applications:

• Video and music storage

There are 3 types of secondary storage.

• Magnetic storage (HDD - hard disk drive).
• Solid State (SSD secondary storage, Stick/USB flash memory).
• Optical Device (CD-R, DVD-RW, Blu-ray Disc).

Cloud Storage

• Remote server (Internet) data storage methods.
• User has access to an internet connection, able to create, edit, and share data files from any location.
• The data and programs are stored remotely from the internet, thus saving space.

Disadvantages of Cloud Storage

• Problem accessing data files when there's a slow unstable internet connection.
• Costs can be high when large storage capacity required.
• Cloud storage company failure.

Advantages of cloud storage:

• The data files stored on the cloud accessed from anywhere on a device with a web browser.
• Users do not need to carry an external storage device and even use the same computer read/write data.
• Data is securely backed up.
• Unlimited storage.

Virtualization

• The ability to hide the nature and access of a computing resource.

Embedded System

• Combination of computer hardware and software that is designed for a specific function.
• Embedded computers are often cheap, low-power devices with limited memory.
• Systems may have a fixed functionality or be programmable.
• Runs a single program that is rarely updated; firmware is stored on ROM.
• Consist of sensors.
• Part of a larger system with other electrical or mechanical parts, such as washing machines.

Internet of Things (IOT)

• Interconnection of digital devices embedded in everyday objects.
• Vast majority of devices connected to the IOT consist of bespoke systems with embedded computers.
• Enhances daily life, creating more productivity and streamlined communication.
• Security and privacy concerns are raised when considering the security all devices and potential hacking.

Software

• Sets of instruction designed to instruct computers what to do.
• Computers consist of both hardware and software.
• Software allows hardware to perform tasks.

Software Types

• The categories of software are system software and application software.
• Application software is word processors, spreadsheets, web browsers, databases, and games.
• System Software is Operating Systems, Utility Programs and Device Drivers.

Operating System

• What runs the background on computer systems.
• OS allows computer systems to function correctly, enabling computers to communicate with human users.
• The OS provides the usability and usable interface for computer user.
• OS perform several functions:
  • Process management
  • Memory management
  • Input/output device management
  • File management
  • User management
  • Human Computer Interface
  • Multitasking

Process Management

• Managing and scheduling tasks with operating systems, as well as resource allocation; involves memory usage and CPU function.
• A computer will be programmed to run more than one program/process simultaneously.
• Processes are given a small amount of time to run (time slice) in the central processing unit.
• The processes are held in queue.
• The O/S switches process at the end of each time slice cycle.
• Processes are placed back into the queue following a completed time slice.
• Processes may be assigned different priorities. The higher priorities can also be assigned larger time periods per slice cycle.
• This process is called scheduling.

Memory Management

• Management deals with the primary memory functionality of the operation system.
• OS moves processes back and forth between main memory and disk as main memory fills.
• This is called paging, swapping, or virtual memory.

Input/output Management

• Uses a device driver to communicate with input and output devices.
• Device drivers translates data from files to be accepted by input/output devices.

User Management

• Systems that allows more than one user login.
• Each person logging into the system gets a user account that is protected by a password and usemame.
• OS can manage different user accounts.

Human Computer Interface

• HCl is the form of a command Line interface or Graphical user interface.
• CLI require a user to type command to choose options;
• GUI allows the user to interact with a computer using picture or icons rather than having to type commands.

Interface: Command Line Interface (CLI)

Advantages

• Direct interaction with the computer.
• The user is not restricted to a specific number of options.
• It is possible to alter computer configuration settings.
• Uses a small amount of computer memory.

Disadvantages

• User needs to know a number of commands.
• Commands need to be typed, creating errors.
• Formatted commands need to be typed and the spelling must be precise.

Interface: Graphical User Interface (GUI)

Advantages

• Users do not need to learn any commands.
• Easy to use with more user-friendly icons.
• An icon that represents an application will open whenever it is clicked through a pointing device.

Disadvantages

• Needs more computer memory than CLI.
• Limited access to icons that are provided on screen.
• Windows needs to operate, therefore using up memory resources.

File Management

• Involves specific tasks such as the ability to create, open, delete, rename, copy and move) and maintain the directory structure and access control (read, write) of file.
• The operating system checks to determine that enough memory usage on secondary devices (HDD/SSD).
• Data is broken into large blocks stored in spaces.
• The blocks reside anywhere on the storage;
• The OS then updates the file allocation table, which includes the start code and sequence of each block.
• Metadata regarding file, such as read/write, date of creation, access are stored independently.

Multitasking

• Computers are able to carry multiple tasks at once.
• Hardware resources (RAM and CPU) are shared by OS controlled processes.

Utility Software

• Utilized for the optimization, maintenance and the management of computer resources.
• Initiated by users, then runs simultaneously.

File Management Tools include:

• Back-up File: to keep data secure by making a back-up copy of files in another location.
• Converting File Formats.
• Compressing file: space usage is compressed by archiving to disk. Access is slower with the utilization.
• Repairing corrupted or damaged files.
• Defragmented (Blocks are moved together to improve system speeds.)

Security Tools

• Anti-Spyware/Anti-Virus detects and prevents malicious code.
• Firewall protection-prevents viruses.

Common Tools

• Notepad or command prompt calculators will come standard.

Simulation and Modelling Software

• Simulation is utilized to analyze or predict what might happen, rather than physically manifesting the project.
• This process may be used to avoid dangerous situations, giving options to help decision making and save on unnecessary costs.

Potential problem:

• The model created is only an output based on factors and estimations, with some margins for error.
• The world is complex.