Introduction to Computer System
Chapter 1: Computer
System Organization
1. A
computer is an electronic device that takes input from the user in the form of
data and instructions, processes this data and produces the result (output) as
information.
2. Arithmetic Logic Unit (ALU): performs the arithmetic (+, –, *, /) and logical (AND, OR, NOT,
XOR) operations on data. It receives input data from the memory, performs
specific operations (addition, subtraction, etc.) or logical operations and the
result is returned to the memory.
3. Control Unit (CU): It controls
the flow of data from input devices to memory and from memory to output devices. It controls and guides the interpretation,
flow and manipulation of all data and information. It does not process the data; instead, it sends control signals
to ALU and memory for carrying out the required operations.
4. A computer
is a combination of hardware and software.
Hardware is
the physical components of a computer like a motherboard, memory device,
monitor, keyboard, etc. Hardware
refers to the physical or tangible (which can be touched) components.
The software
is a set of programs or instructions. In other words, software is the code
necessary to operate/run the computer hardware.
5. Software
is a set of programs that are designed to perform a well-defined function. A
program is a sequence of instructions written to solve a particular problem and
to make the hardware run. All the programs used in a computer to perform
specific tasks are called software.
6. Here are some examples
of hardware components
commonly found in computer:
- Central Processing Unit (CPU) – the “brain”
of the computer that processes
data and instructions.
- Random Access Memory (RAM) – a type of memory that temporarily stores data and instructions
for the CPU to access quickly.
- Hard Disk Drive (HDD) –
a storage device that stores data and programs.
- Motherboard – a circuit board that connects all computer components.
- VDU (Visual
Display Unit) – a monitor
or screen that displays the output of the computer.
- Keyboard – an input device that allows the user to input text and commands.
- Mouse – an input
device that allows
the user to control and navigate the cursor.
7. An
Operating System (OS) is software that manages and controls a computer system’s
hardware and software resources. It provides an interface between the user and
the computer system and helps in executing user programs.
The different types of operating system are:
1. Single User Operating
System: These are designed
to be used by only one user at a time. For example, Microsoft Windows, MacOS, and Linux.
2. Multi-User Operating Systems:
These
allows multiple users to access a computer
simultaneously and share resources efficiently. For example, Unix,
Linux, etc.
3. Distributed
Operating Systems: These manage multiple
interconnected computers working together as a single system. For example, Google Chrome’s OS, Linux, etc.
4. Mobile Operating Systems:
These are designed for smartphones and tablets. For example,
Android (Google), iOS (Apple), etc.
8. Without
hardware, the software cannot be used. Software needs hardware to perform
functions. For example, a software
application like Microsoft Word needs the hardware components of a computer, such as the CPU, RAM and hard
drive, to run and operate. Without these hardware components, the software
cannot function.
Similarly, hardware
is of no use without
software. Hardware needs software to control and manage
its operations. For example, the hardware components of a printer, such as the
print head and ink cartridges, need software drivers to operate and communicate
with the computer. Without the software drivers, the printer cannot function.
9. The
software can be broadly categorized into four types depending on their
functions and user requirement:
(a) System Software: System software manages and controls the
hardware and other software components of a computer system. Examples include
operating systems like Windows, macOS, and Linux.
(b) Application
Software: Application
software is designed
to perform specific
tasks or functions, such as word processing,
accounting, or graphics. Examples include Microsoft Office, Adobe Photoshop and
QuickBooks.
(c) Utility Software: Utility software is used to maintain and
optimize the performance of a computer system.
Examples include antivirus software, disk cleaners
and file compression tools like WinZip.
(d) Programming Tools: Programming software is used to write, debug
and develop software programs. Examples include compilers, debuggers and
Integrated Development Environments (IDEs) like Visual Studio and Eclipse.
10. An operating system (OS) is a program
that acts as an interface between the user and the hardware of the
computer. The OS helps to manage the resources of the computer
and optimize its performance. An OS is the first program to be executed
on a computer after the BIOS (Basic Input Output System). OS performs all basic
tasks such as identifying basic input/output devices, accepting input from the
input devices, sending results to the output devices, keeping track of files
and directories on the disk and controlling other peripheral devices such as
disk drives and printers.
Two popular operating systems
are:
- Microsoft Windows
- Apple macOS
- Linux OS
The
software required to make a computer functional includes an operating system (OS).An operating system is a type of system software
that manages computer
hardware and software
resources and provides common services for computer programs. The two
primary services of an operating system are:
Resource Management: An operating system manages the computer hardware
resources such as CPU, memory, storage, and input/output
devices, and ensures that they are used efficiently and effectively by
different computer programs.
User Interface: An operating system provides a
user interface that allows users to interact with the computer and its
applications. This can be in the form of a graphical user interface (GUI) or a
command-line interface (CLI), depending on the operating system.
Block Diagram
of a Computer System
11. The basic architecture of a computer
consists of the following components:
(a) Central Processing Unit (CPU): The CPU is the “brain”
of the computer and is responsible
for executing instructions. It consists of an arithmetic and logic unit (ALU),
a control unit, and registers.
(b) Memory: The memory is used to store data and instructions that the
CPU needs to access quickly. There are two types of memory – primary memory
(RAM) and secondary memory (hard disk, SSD).
(c) Input Devices: Input devices such as a keyboard, mouse or touchpad, allow
users to interact with the computer
by providing input.
(d) Output Devices: Output devices such as a monitor or printer, display or print
the results of the computer’s processing.
(e) Storage devices:
Storage devices,
such as hard disks, SSDs or USB drives are used to store data and programs.
12. Central Processing
Unit (CPU) is the control centre or brain of a computer. It guides, directs,
controls and governs all the processing that takes place
inside the computer. The CPU consists
of three components— ALU, CU and Registers.
(a) Arithmetic Logic Unit (ALU): All calculations and comparisons are made in
this unit. The ALU performs the arithmetic (+, –, *, /)
and logical (AND, OR, NOT, XOR) operations.
(b) Control Unit (CU): It controls the flow of data from input
devices to memory and from memory to output devices.
It controls and guides the interpretation, flow, and manipulation of all data and
information. It does not process
the data; instead,
it sends control
signals to ALU and memory for
carrying out the required operations.
(c) Registers:
Registers are high-speed temporary
storage areas found in the CPU. Registers
work as per the instructions given by the control unit (CU), storing
instructions and data, immediately required for operation.
13. CU
controls all the functions like input, output, storage and process. It instructs
ALU which operation is to be carried out. So, the control unit is referred to
as the central controller of a computer.
14. An Arithmetic and Logic Unit (ALU) in a computer
works in coordination with other units, primarily the control unit and the memory unit.
The ALU is responsible for performing arithmetic and logical operations such as addition, subtraction, multiplication, division and comparison. However,
it does not function independently as it needs instructions and data from
memory and the control unit directs its operations.
The control unit retrieves instructions from memory
and sends them to the ALU to perform the appropriate operation. After the operation is completed, the result is stored back in memory or sent to
the output unit for display. The control unit also directs the flow of data and
instructions within the computer and coordinates the operations of other components, including the ALU.
COMPUTER MEMORY
Memory is a critical component of a computer system that plays a vital role in its functioning. It refers to the storage space that a computer uses to store data and instructions for the CPU to access quickly. The primary role of memory in the functioning of a computer is to provide fast and efficient access to data and instructions that the CPU needs to perform its tasks.
There are two main types of memory in a computer:
(a) Primary Memory
(b) Secondary Memory
Volatile
memory is a type of computer memory that requires power to retain data. When
power is removed, the data stored in volatile memory is lost. The most common
example of volatile memory is Random Access
Memory (RAM). RAM is used to temporarily store data and instructions that are actively being used by the computer
system. It provides
fast access to data and instructions that the CPU needs
to perform its tasks. The main advantage of volatile memory
is that it is very fast, but the disadvantage is that it is temporary, and
data cannot be stored in it permanently.
Non-volatile memory is a type of computer memory that can retain data even when power is removed.
This makes it ideal for storing data and instructions that need to be kept for
a long time, such as system programs or user data. Examples of non-volatile
memory include Read-Only Memory (ROM), flash memory and hard disk drives. Non-volatile memory is slower than volatile
memory, but it can store data
permanently.
Primary storage
devices are devices
that are used to store data temporarily in a computer system. The data stored in primary storage devices are directly
accessible by the CPU and are used to hold the instructions and data that are currently
being used by the computer
system. Here
are the types of primary storage devices:
(a) Random Access Memory (RAM)
(b) Read-Only Memory (ROM system)
(c) Cache Memory
(a) Random Access Memory (RAM): It is a read/write memory as it is possible
to both read from and write to a location within RAM. It is used for primary
storage in computers to hold active information of data and instructions. The
RAM is a volatile memory as it does not store data and instructions permanently
and loses its contents when the power is switched off or interrupted. RAM
provides faster access than secondary memory with less memory access time.
(b) Read-Only Memory (ROM): It is a read-only memory, i.e., the data and instructions are
placed in the ROM at the time of its manufacturing and can’t be changed thereafter. It is a permanent and non-volatile memory as it does not lose its contents when the power is switched
off or interrupted. ROM is slower than RAM and is used to hold certain
essential instructions to check basic hardware
components such as booting, procedures to load the operating system, and
frequently needed functions.
(c) Cache Memory : Cache memory is a chip-based computer component that makes retrieving data from the computer's memory more efficient. It acts as a temporary storage area that the computer's processor can retrieve data from easily. This temporary storage area, known as a Cache, is more readily available to the processor than the computer's main memory source, typically some form of DRAM.
Secondary storage
devices are used to store a large amount of data permanently which is not possible
by using the primary or main memory. The amount of data a disk can hold is defined as Disk Capacity, which is measured
in terms of bytes, kilobytes
(KB), megabytes(MB) and so on.
The most common secondary
storage devices are:
Memory Cards: These are data storage devices, also called Flash memory
cards. They are mainly used with digital cameras, computers, mobile phones,
music players, video game consoles, etc. They offer high recording ability with
power-free storage. Memory cards come with a storage capacity of 8 GB, 16 GB, 32 GB, 64 GB, and 128 GB.
Memory cards are small, portable storage
devices used to store digital
data, such as photos, videos and music files. They are commonly
used in cameras, smartphones, tablets and other portable devices. Memory cards
use flash memory technology to store data and come in various sizes, capacities
and formats. In this response, we will discuss
the different types
of memory cards.
(c) CompactFlash(CF) Cards: CF cards are larger than SD cards and were
commonly used in professional cameras before SD cards became more prevalent.
They have a higher capacity and faster transfer
rates than SD cards but they are less common and more expensive.
UNITS OF MEMORY
S. No. Unit Description1.
Binary Digit 1 Bit (0 or 1)2.
Byte 1 Byte = 8 Bits
3.
Kilobyte (KB) 1 KB = 1024 Bytes4.
Megabyte (MB) 1 MB = 1024 KB
5.
Gigabyte (GB) 1 GB = 1024 MB6.
Terabyte (TB) 1 TB = 1024 GB
7.
Petabyte (PB) 1 PB = 1024 TB8.
Exabyte (EB) 1 EB =1024
PB
9.
Zettabyte (ZB) 1 ZB = 1024 EB10.
Yottabyte (YB) 1 YB = 1024 ZB
11.
Brontobyte (BB) 1 BB = 1024 YB12.
Geopbyte 1 Geop Byte = 1024 BB
INPUT UNIT
An input unit is a device that allows the user to input data or instructions into a computer. This data can be in various forms such as text, images, audio or video. Examples of input devices include a keyboard, mouse, touchpad, scanner, microphone and camera. The significance of an input unit is that it enables the user to interact with the computer and provide it with the necessary instructions and data. Without an input unit, the computer would not be able to receive any input from the user making it impossible to perform any useful task.Some example of input devices:
(a) Keyboard: The most commonly used input device is the keyboard which takes the data in the form of letters, digits and commands into the computer. A computer keyboard possesses additional keys in contrast to a traditional typewriter, such as function keys, alphanumeric keys, direction keys and other keys (Special and lock keys).
(b) Biometric Sensor: It is an input device that is used to uniquely identify a person based on his physical or behavioural traits. Biometric sensors can scan human characteristics such as eyes, fingerprints, etc. It is commonly used to mark the attendance of employees/students in organizations/ institutions.
(c) Magnetic Ink Character Reader (MICR): MICR is a technology used in banking to detect the numbers printed with magnetically charged ink at the bottom of bank cheques and convert them into digital data. These digital numbers represent the bank account number, bank branch and cheque number.
(d) Mouse: A mouse is a pointing device with a roller at its base, used for moving pointer on a computer monitor. It converts the movements of the user’s hand into a unique set of binary digits representing the position of the mouse at a particular instant. When a user moves a mouse across a flat surface, the pointer moves in the direction of the mouse’s movement.
(e) Bar Code Reader: A bar code is a collection or a sequence of lines of different heights and widths that are printed on various types of products. The machine that reads these bar codes is called a bar code reader. It consists of a light source, a lens, and a light sensor which translates optical impulses into electrical signals. Also, it contains decoder circuitry which analyzes the bar code’s image data and sends the bar code’s content to the scanner’s output port.
(f) Light Pen: A light pen is an input device that allows the user to interact with a computer screen by pointing to and selecting specific areas on the screen.
OUTPUT UNIT
An output unit is a device that provides output from a computer system to the user in a human-readable format. It works by receiving data or instructions from the computer and then displaying or printing it in a format that the user can understand.Output devices come in various forms, depending on the type of output they produce. Some examples of output devices include:
(a) Monitor: A monitor displays visual output from a computer in the form of text, images or video.
Visual Display Unit (VDU): It is the most common device for displaying the output of computer- processed information. It displays information in the same way as it is seen on a television screen. The monitor is also called Visual Display Terminal (VDT) or Visual Display Unit (VDU). The different types of monitors are CRT (Cathode Ray Tube), LCD (Liquid Crystal Display), LED (Light Emitting Diode), and OLED (Organic Light-Emitting Diode).
(b) Printer: A printer produces hard copies of documents or images on paper.
Types of Printer
Impact Printer: There is a mechanical contact between the printer head and the paper.
Non-impact Printer: No mechanical contact between the printer head and paper.
Examples:
Inkjet: An inkjet printer is the most common type of low-cost printer. It uses the technique of spreading quickly dry ink on paper. The ink is stored in the form of cartridges of different colors (red, green, black, and yellow). These printers generate high-quality prints and are ideal for small offices and homes.
LaserJet: A laser printer is a type of non-impact printer that uses laser technology to produce high quality text and graphics on paper. It works by using a laser beam to create an electrostatic image or pattern on a photosensitive drum, which is then developed with toner particles and transferred onto paper. The toner is then fused onto the paper with heat and pressure to create a permanent image.
(c) Plotters : Plotters are the output devices that are used for producing good-quality images and drawings. Unlike printers, they support the printing of large-sized papers. They are mainly used in Computer Aided Design (CAD).
(d) Speaker: A speaker produces audio output from a computer, such as music or sound effects.
LANGUAGE PROCESSOR
(TRANSLATOR PROGRAMS)
Assembler: Assembler is used to translate the program written in assembly language into machine code. The input of the assembler is a source program that contains assembly language instructions. The output generated by the assembler is the object code or machine code which is understandable by the computer.
Compiler: The language processor that translates the complete source program as a whole in one go into machine code is called a compiler. The program translated into machine code is called the object program. The source code is translated into object code successfully if it is free from errors. If there are any errors in the source code, the compiler specifies the errors at the end of the compilation with line numbers. The errors must be removed before the compiler can successfully recompile the source code. Some of the examples are C and C++ compilers.
Interpreter: The language processor that translates a single statement of source program into machine code and executes it immediately before moving on to the next line is called an Interpreter. If there is an error in the statement, the interpreter terminates its translating process at that statement and displays an error message. Only after the removal of the error does the interpreter move on to the next line for execution. Some of the languages that use interpreters are Python, PHP, MATLAB, etc
