COMPUTER SCIENCE

1. What will happen if we turn on a computer?
Powering on the computer
The processor gives the CPU program counter a F000
hexadecimal number. This number tells the CPU that it's
ready to process the instructions at this location contained
in the basic input/output system (BIOS).
BIOS and the POST
How Does a Computer Work? (computerhope.com)
BIOS performs POST.IF POST is accurately completed
then the operating system start loading.

2. Power on
Computer
BIOS performs POST
Disk RAM
Loading of OS
FIGURE:BIOS-POST operation

3. CENTRAL PROCESSING UNIT
The CPU is the primary component that executes
instructions and processes data in a computer system.
The central processing unit (CPU) performs operations
on data.
In most architectures it has three parts:
1.An arithmetic logic unit (ALU)
2.A control unit
3.A set of registers(fast storage locations)

4. 2.Arithmetic Circuitry:
1. Adder/Subtractor: This usually involves cascading multiple full adder circuits
to handle multi-bit operands.
2. Incrementer/Decrementer: The ALU may have dedicated circuitry to
increment or decrement a value by one.
3. Multiplier/Divider (optional): perform multiplication and division operations.
2.Logical Circuitry:
1.OR Gate: OR gates are used to perform logical OR operations on bits of binary data.
2.AND Gate: The ALU includes AND gates to perform logical AND operations on
individual bits of binary data.
3.XOR Gate: XOR gates are used to perform exclusive OR operations, comparing the bits
of two operands.
4.NOT Gate: The ALU may include NOT gates to perform logical negation (complement)
operations.

5. CONTROL UNIT
The third part of any CPU is the control unit. The control unit controls
the operation of each subsystem. Controlling is achieved through signals
sent from the control unit to other subsystems.
There are two types of control units:
1.Hardwired control unit and
2.Microprogrammable control unit.
https://www.geeksforgeeks.org/introduction-of-control-unit-
and-its-design/

6. RESISTERS
Registers are fast stand-alone storage locations that hold data
temporarily. Multiple registers are needed to facilitate the
operation of the CPU
1.Data resister
2.Instruction resister
3.Programme counter

7. .
Instruction Register(IR) : Holds the last instruction fetched.
Registers Involved In Each Instruction Cycle:
Memory address registers(MAR) : It is connected to the address lines
of the system bus. It specifies the address in memory for a read or
write operation.
Memory Buffer Register(MBR) : It is connected to the data lines of the
system bus. It contains the value to be stored in memory or the last
value read from the memory.
Program Counter(PC) : Holds the address of the next instruction to
be fetched

8. 1.Fetch instruction from memory.
2.Decode the instruction.
3.Read the effective address from
memory.
4.Execute the instruction.
Instruction cycle

9. Pipelining is the process of storing and prioritizing computer
instructions that the processor executes.
Pipelining
Types of pipelines
1.Instruction pipeline
2.Arithmetic pipeline
Advantages of pipelining
The biggest advantage of pipelining is that it reduces the processor's cycle
time. This is because it can process more instructions simultaneously, while
reducing the delay between completed instructions
https://www.techtarget.com/whatis/definition/pipe

10. Memory
The memory unit consists of cache memory and primary memory. Primary memory or
main memory of the computer is used to store the data and instructions during
execution of the instructions

11. RAM
o Primary storage of a computer is often referred to as RAM
because of its random access capability
o RAM chips are volatile memory
o A computer’s motherboard is designed in a manner that
the memory capacity can be enhanced by adding more
memory chips
o The additional RAM chips, which plug into special sockets
on the motherboard, are known as single-in-line memory
modules (SIMMs)
 ROM a non-volatile memory chip
 Data stored in a ROM can only be read and used – they
cannot be changed
 ROMs are mainly used to store programs and data, which
do not change and are frequently used. For example,
system boot program
ROM

12. Allows information output, from the computer to the
outside world. Example: Printer, Monitor etc
Allows user input, from the outside world to the
computer. Example: Keyboard, Mouse etc.
Input Output device
 Primary Function
a. Input Devices: These devices are primarily used for data or command input into the computer
system. Examples include keyboards, mice, scanners, and microphones.
b. Output Devices: These devices are primarily used for presenting or outputting information from the
computer system. Examples include monitors, printers, speakers, and projectors.
Categorize Input And Output
Devices
 Connectivity
a. Wired Devices: These devices are physically connected to the computer system using cables or
wires. Examples include USB keyboards, Ethernet network adapters, and wired mice.
b. Wireless Devices: These devices connect to the computer system using wireless technologies such
as Bluetooth or Wi-Fi. Examples include wireless keyboards, wireless mice, and wireless
headsets.

13. Presenting
Binoy Barman
Bus system
 Address lines (AL)
 Data lines (DL)
 Control lines (CL)
Operating
system
 Types of Operating system
 Key functions and
components of an
operating system
Topic

14. Definition and function of the bus system: The bus system is a communication
pathway that allows data and control signals to be transmitted between components
Bus System
 The bus is a communication channel.
 The characteristic of the bus is shared
transmission media.
 The limitation of a bus is only one transmission
at a time.
 A bus used to communicate between the major
components
System bus contains 3 categories of lines
used to provide the communication
between the CPU, memory and IO named
as:
 Address lines (AL)
 Data lines (DL)
 Control lines (CL)

15. 1. Address Lines:
•Used to carry the address to memory and IO.
•Unidirectional.
•Based on the width of an address bus we can determine the capacity of a
main memory
2. Data Lines:
•Used to carry the binary data between the CPU, memory and IO.
•Bidirectional.
•Based on the width of a data bus we can determine the word length of a
CPU.
•Based on the word length we can determine the performance of a CPU.
3. Control Lines:
•Used to carry the control signals and timing signals
•Control signals indicate the type of operation.
•Timing Signals are used to synchronize the memory and IO operations with a
CPU clock.
•Typical Control Lines may include Memory Read/Write, IO Read/Write, Bus
Request/Grant, etc.

16. Types of Operating system
Types of
Operating
system
Embedded
Operating
Systems
Cluster Operating
Systems
Multi-User
Operating
Systems
Single-User
Operating
Systems
Multiprocessing
Operating System
Network
Operating System
Time-sharing
Operating System
Batch Operating
System
 Batch Operating System
 Time-sharing Operating System
 Distributed Operating System
 Network Operating System
 Real-time Operating System
 Multiprocessing Operating System
 Single-User Operating Systems
 Multi-User Operating Systems
 Embedded Operating Systems
Operating system
An Operating System (OS) is an interface between a computer
user and computer hardware. An operating system is a software
which performs all the basic tasks like file management, memory
management, process management, handling input and output,
and controlling peripheral devices such as disk drives and
printers.

17. Process Management:
The operating system manages processes, which are programs in execution. It schedules
processes, allocates system resources (such as CPU time and memory), and facilitates
communication and synchronization between processes.
Memory Management:
The OS handles memory allocation, ensuring that each process has sufficient memory to
execute. It manages virtual memory, which allows processes to use more memory than
physically available by utilizing secondary storage (e.g., hard disk) as an extension of RAM.
File System Management:
The operating system provides a file system that organizes and manages files and directories
stored on storage devices. It handles file creation, deletion, access permissions, and ensures
data integrity and security.
Key functions and components of an
operating system
Security and
Protection
Process
Management
Memory
Management
File System
Management
Networking and
Communication
User Interface
Device
Management

18. Device Management:
The OS interacts with hardware devices such as input/output devices (e.g.,
keyboard, mouse, printers) and storage devices (e.g., hard drives, solid-state drives).
It manages device drivers, facilitates device communication, and provides a
uniform interface for applications to access devices.
User Interface:
The operating system provides a user interface that allows users to interact with
the computer system. This can be a command-line interface (CLI) where users
type commands, or a graphical user interface (GUI) with icons, menus, and
windows for intuitive interaction.
Networking and Communication:
Operating systems provide networking capabilities to enable communication
between computers and devices in a network. They manage network protocols,
handle data transmission, and facilitate network resource sharing.
Security and Protection:
The OS implements security mechanisms to protect the system and
user data. This includes user authentication, access control, encryption,
and detection/prevention of malicious activities.