Structure And Organization of Computer System (part-1)


STRUCTURE AND ORGANIZATION OF COMPUTER SYSTEM 

computer parts
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We will discuss:

  • Computer Operations
  • Basic Computer Organization
  • Computing Systems    

                Hardware          

  •                 Hardware: Central Processing Unit (CPU)
  •                 Hardware: Random Access Memory (RAM)
  •                 Hardware: Secondary Memory (Disk)
  •                 Hardware: The Bus
  •                 Hardware: Cache memory

               Software 

  •                 Operating System (OS):
  •                 Software: Applications

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Computer Operations

A computer is a machine that can be programmed to carry out a set of instructions. It can be used to do many things, such as:

  • Store data
  • Process data
  • Generate output
  • Control other devices

The basic operations of a computer are:

  • Input: This is the process of entering data into the computer. Data can be entered through a variety of devices, such as a keyboard, mouse, scanner, or microphone.
  • Processing: This is the process of manipulating data. The computer can perform mathematical operations, such as addition and subtraction, as well as logical operations, such as AND and OR.
  • Output: This is the process of displaying the results of processing. Output can be displayed on a screen, printed on paper, or stored in a file.
  • Storage: This is the process of keeping data for future use. Data can be stored on a variety of devices, such as a hard drive, flash drive, or cloud storage.
  • Control: This is the process of managing the computer's resources. The computer's operating system controls how the hardware and software interact with each other.

In addition to these basic operations, computers can also be used to:

  • Communicate with other computers
  • Access the internet
  • Run programs
  • Create and edit documents
  • Play games

Computers are becoming increasingly powerful and versatile. They are used in a wide variety of applications, from personal computers to supercomputers.

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Basic Computer Organization

A computer has five essential components:

  • Input unit: This is the part of the computer that takes in data from the user. The input unit can be a keyboard, mouse, microphone, scanner, or other device.
  • Memory: This is the part of the computer that stores data and instructions. The memory can be divided into two parts: the main memory and the secondary memory. The main memory is where the data and instructions are stored while the computer is running. The secondary memory is where data and instructions are stored when the computer is turned off.
  • Processing unit: This is the part of the computer that performs calculations and logical operations. The processing unit is also called the central processing unit (CPU).
  • Output unit: This is the part of the computer that displays the results of the processing. The output unit can be a monitor, printer, speaker, or other device.
  • Control unit: This is the part of the computer that controls the other components. The control unit tells the input unit what data to read, the processing unit what to do with the data, and the output unit where to send the results.

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Computing Systems

A computer system is made up of two main parts: hardware and software.

  • Hardware is the physical part of the computer, such as the CPU, memory, storage devices, and input/output devices.
  • Software is the set of instructions that tells the hardware what to do. Software can be divided into two main types: operating systems and applications.

Here are some additional things to know about computing systems:

  • The hardware and software work together to make the computer function.
  • The hardware is responsible for carrying out the instructions of the software.
  • The operating system is the most important piece of software on a computer.
  • Applications are the programs that users interact with to get things done.

 

Hardware

Hardware: Central Processing Unit (CPU)

The CPU is the brain of the computer. It is responsible for carrying out the instructions of the software. The CPU has two main parts: the arithmetic logic unit (ALU) and the control unit.

  • The ALU performs arithmetic and logical operations, such as addition, subtraction, multiplication, and division.
  • The control unit tells the ALU what to do and coordinates the activities of the other parts of the CPU.

The speed of the CPU is measured in megahertz (MHz) or gigahertz (GHz). One MHz is equal to one million clock ticks per second. One GHz is equal to one billion clock ticks per second.

Some common examples of CPUs are:

  • Intel Pentium
  • AMD K6
  • Motorola PowerPC
  • Sun SPARC

Here are some additional things to know about the CPU:

  • The CPU is the most important part of the computer.
  • The speed of the CPU determines how fast the computer can run.
  • The CPU is made up of millions of transistors.
  • The CPU is cooled by a fan or heat sink.

Hardware: Random Access Memory (RAM)

RAM is the main memory of a computer. It is called "random access" because any byte of memory can be accessed (read or written to) in equal time. RAM is much faster than other types of memory, such as hard drives or solid-state drives. However, RAM is volatile, which means that the data stored in it is lost when the power is turned off.

RAM is equal to a person's short-term memory. It is used to store the data that the computer is currently using. This includes the operating system, programs, and data that are being processed.

RAM is measured in bytes. A byte is a group of 8 bits. A bit is the smallest unit of data that a computer can store.

Common units of RAM measurement:

  • Kilobyte (KB): 1024 bytes
  • Megabyte (MB): 1024 KB
  • Gigabyte (GB): 1024 MB
  • Terabyte (TB): 1024 GB
  • Petabyte (PB): 1024 TB

Here are some additional things to know about RAM:

  • The amount of RAM that a computer needs depends on the tasks that it will be used for.

 

Hardware: Secondary Memory (Disk)

Secondary memory is a type of computer memory that is used to store data and programs permanently. It is called "secondary" because it is slower than the main memory (RAM). However, secondary memory is non-volatile, which means that the data stored in it is not lost when the power is turned off. It is also used to store programs that are not currently being used by the computer.

Secondary memory is typically divided into two types: magnetic storage and optical storage.

  • Magnetic storage uses magnetic fields to store data. Examples of magnetic storage devices include hard drives, floppy disks, and magnetic tapes.
  • Optical storage uses lasers to store data. Examples of optical storage devices include CDs, DVDs, and Blu-ray discs.

Here are some additional things to know about secondary memory:

  • It has a much larger capacity.

Here are some examples of secondary memory devices and their capacities:

  • Floppy disk: 1.44 MB
  • Hard disk: 1 TB - 100 TB
  • CD-ROM: 700 MB
  • DVD-ROM: 4.7 GB - 17 GB
  • Blu-ray Disc: 25 GB - 128 GB

The capacity of a secondary memory device depends on the technology used and the size of the device. For example, a hard drive can have a capacity of several terabytes, while a floppy disk can only store a few megabytes of data.


Hardware: The interconnected components

The interconnected components of a computer are the parts that work together to make the computer function. These components include:

  • The CPU (central processing unit)(arithmetic logic unit + control unit)
  • The memory subsystem(main memory + secondary memory)
  • The I/O subsystem (input/output subsystem) 

These components are interconnected by a bus, which is a pathway that allows data and signals to be transferred between them.


Hardware: The Bus

A bus is a pathway that allows data and signals to be transferred between the different components of a computer. It is analogous to the spinal cord in the human body, which carries signals between the brain and the rest of the body.

The bus is measured in megahertz (MHz), like the CPU. However, the bus is typically much slower than the CPU. This is because the bus has to share its bandwidth with all of the other components in the computer.

The bus is a bottleneck in most of today's PCs. This means that the speed of the bus is the limiting factor in how fast the computer can run.

Here are some additional things to know about the bus:

  • The bus is made up of a set of wires.
  • The width of the bus determines how much data can be transferred at once.
  • The bus is a shared resource, which means that all of the components in the computer have to share its bandwidth.

The three main types of buses in a computer are:

  • Address bus: The address bus is a set of parallel wires that carries the address of the memory location or device that the CPU wants to access. The width of the address bus determines the amount of memory that the system can address. For example, a 32-bit address bus can address 4GB of memory.
  • Data bus: The data bus is a set of parallel wires that carries the data between the CPU and other components in the system. The width of the data bus determines the amount of data that can be transferred between the CPU and other components at a time. For example, a 64-bit data bus can transfer 64 bits of data at a time.
  • Control bus: The control bus is a set of parallel wires that carry control signals from the CPU to other components in the system. These control signals tell the other components what to do with the data on the data bus. For example, the control bus might carry signals that tell the memory controller to read or write data, or that tell a device to start or stop operating.
How the address bus, data bus, and control bus work together:
Suppose you want to read the data stored in the memory location at address 0x1234. The CPU would send the following signals on the bus:
  • Address bus: 0x1234
  • Control bus: Read
This tells the other components in the system that the CPU wants to read the data at address 0x1234. The memory controller would then read the data from memory and send it to the CPU on the data bus.
The CPU would then be able to process the data or store it in a register.

The address bus, data bus, and control bus work together to allow the CPU to communicate with other components in the system. The address bus tells the other components where to find the data that the CPU wants to read or write. The data bus carries the data itself. The control bus tells the other components what to do with the data.

I/O bus or local bus:

  • In today's computers, the I/O controller will have an extra bus called the I/O bus.
  • The I/O bus will access all other I/O devices connected to the system.
  • For example, the I/O bus might be used to access the keyboard, mouse, and hard drive.
  • The I/O bus is typically faster than the address bus and data bus because it is only used to access I/O devices.

Hardware: Cache memory

Cache memory is a small but fast memory that is used to store recently used instructions and data. It is located close to the CPU, so it can be accessed much faster than the main memory (RAM).

Cache memory works by storing copies of the data that is most frequently used by the CPU. When the CPU needs to access a piece of data, it first checks the cache memory. If the data is in the cache memory, the CPU can access it very quickly. If the data is not in the cache memory, the CPU must access the main memory. This is slower because the main memory is further away from the CPU.

Cache memory can significantly improve the performance of a computer by reducing the amount of time that the CPU has to wait for data.

Here are some additional things to know about cache memory:

  • Cache memory is typically made up of static RAM (SRAM), much faster than dynamic RAM (DRAM), which is used for main memory.
  • Cache memory is typically organized in a hierarchy, with smaller and faster caches closer to the CPU and larger and slower caches further away from the CPU.
  • The size of the cache memory is typically measured in kilobytes (KB) or megabytes (MB).
  • The speed of the cache memory is typically measured in nanoseconds (ns).

  

Hardware: Summary

  • Programs are stored in secondary memory, such as a hard drive or a solid-state drive.
  • When a program is needed, it is loaded into the main memory (RAM).
  • The CPU retrieves and executes the statements in the program.
  • When the program is finished, it is unloaded from the main memory.

Here are some additional things to know about hardware:

  • The hardware is the physical part of the computer.
  • The hardware includes the CPU, memory, storage devices, and input/output devices.
  • The software is the instructions that tell the hardware what to do.
  • The software is stored in the secondary memory.
  • The hardware and software work together to make the computer function.



Software 

Operating System (OS):

  • The operating system is a software program that manages the computer's hardware and software resources.
  • It is loaded from secondary memory into main memory when the computer is turned on.
  • It remains in memory until the computer is turned off.
  • The OS acts as the "manager" of the system, making sure that each hardware device interacts smoothly with the others.
  • It also provides the interface by which the user interacts with the computer.
  • The OS provides a set of basic services that are essential for the computer to function, such as:

Managing memory
Managing files
Managing processes
Providing a user interface

Here are some additional things to know about the operating system:

  • The operating system is a critical part of the computer system. Without an operating system, the computer would not be able to function.
  • Many different operating systems are available, each with its own strengths and weaknesses.
  • Some popular operating systems include Windows, macOS, Linux, and Android.


Software: Applications

Software applications are programs that perform specific tasks for the user. They are not part of the operating system, but they run on top of the operating system.

  • Word processors are used to create and edit text documents.
  • Spreadsheets are used to create and manage spreadsheets.
  • Databases are used to store and retrieve data.
  • Web browsers are used to view web pages.
  • C++ compilers are used to compile C++ code into machine code.

Software applications are typically written in programming languages, such as C++, Java, or Python. They can be purchased or downloaded from the internet. They can be installed on a computer or accessed through a cloud-based service.

Here are some additional things to know about software applications:

  • Software applications are essential for the user to interact with the computer and perform tasks.
  • There are many different software applications available, each with its own purpose.
  • Some popular applications include Microsoft Office, Google Apps, and Adobe Creative Suite.


How a program is run on a computer:

  1. The program is stored on disk.
  2. The user launches the program.
  3. The operating system (OS) controls the CPU and loads the program from disk to RAM.
  4. The OS then relinquishes the CPU to the program, which begins to run.

Here are the details of each step:

  • The program is stored on a disk in a file. The file is typically a binary file, which means that it is made up of machine code that can be directly executed by the CPU.
  • The user launches the program by clicking on an icon or by typing a command in the terminal.
  • The OS controls the CPU and loads the program from disk to RAM. The OS uses a process called memory management to allocate memory to the program.
  • The OS then relinquishes the CPU to the program, which begins to run. The program can then access the data and instructions that are stored in RAM.

Here are some additional things to know about how programs are run on a computer:

  • The CPU can only run one program at a time. However, the OS can switch between programs very quickly, so it appears that multiple programs are running at the same time.
  • The OS uses a technique called multitasking to allow multiple programs to run at the same time. Multitasking is achieved by time-sharing the CPU between the different programs.
  • The OS also uses a technique called interrupts to allow programs to interact with each other and with the user. Interrupts are signals that are sent to the CPU from other devices, such as the keyboard and mouse.
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Summary:

A computer performs fundamental operations: input, processing, output, storage, and control. Hardware components include the CPU (central processing unit), RAM (random access memory), secondary storage, and interconnected buses. Cache memory improves CPU performance. Software comprises the operating system (OS) and applications. The OS manages hardware and provides user interfaces, while applications perform specific tasks. Programs are loaded from secondary storage into RAM by the OS and run on the CPU. Multitasking enables multiple programs to run simultaneously. Interrupts allow interaction with devices. Together, hardware and software collaborate to make computers versatile tools for data processing, communication, and various applications, enhancing productivity and capabilities.


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