Computer System Architecture

This presentation provides an overview of computer system architecture, including the CPU, memory unit, and subsystems. It explains the purpose and operation of the CPU, different types of operating systems, and key features associated with OS architecture. The presentation also covers the services provided by an operating system and the importance of resource allocation and protection.

COMPUTER SYSTEM
ARCHITECTURE
(Computer Systems and Operating Systems)

COMPUTER SYSTEM
A system that includes computer with the other software
and peripheral devices that are necessary for it to
function is known as computer system. This system has
ability to:
 Accept data and information
 Input, store and implementation of instructions.
 Perform arithmetical and logical operations
 Output results as per the requirement of user.

SUBSYSTEMS OF A COMPUTER
 The main subsystems of a computer systems are as
follows:
 Central Processing Unit
 Storage Unit
 I/O devices

ORGANISATION AND CONNECTION OF
COMPUTER SUBSYSTEMS:
 Input and Output Systems: They are organised in a
way that they both are connected to the I/O unit through
buses. There are three set of lines for buses, they are:
address, data and control. Address line reflects the
processing of data and they are unique for an
input/output device. Control lines are those which
recognises the responses of these address to the
command of user. Further, the data is placed on the data
lines.

CONT.
Depending on these three lines, these input systems are
connected to each other.
 Hardware that are required to connect input devices to
bus includes:
 Interface circuits such as address decoders, control
circuits, data registers and status registers.
 Registers in I/O interface for buffering and control.
 Flags in status registers
 Data registers.

MEMORY/STORAGE UNIT
 There are two types of memory units, namely primary or
main memory and secondary storage. Primary one is
organised internally the computer system whereas
secondary memory is present external to the system.
Main memory covers RAM and ROM which are directly
connected to the central processing unit.

CENTRAL PROCESSING UNIT:
 There are several components inside a CPU, such as
arithmetic logical unit, control unit, and registers. The
ALU and CU reads the data either from main memory or
from secondary memory through I/O unit. With the help
of cross-communication buses CPU is connected to the
main memory and I/O units. The data given by these
sources are read and dealt by the component of central
processing unit.

PURPOSE AND OPERATION OF
THE CPU
 Central processing unit of a computer system is regarded
as its brain. It is a electronic circuit that holds the
instructions of a program by doing basic arithmetic and
logical operations, control and input-output instructions
given by the user. There are three major components of
CPU, namely ALU, CU and registers.

CONTROL UNIT
 Control Unit (CU): It is responsible for controlling the
operations of the processor. The operations of these units
are performed by issuing the control signals to the other
areas of the processors. To them, instructions are
provided to make choice between what to perform and
what not to perform.

ARITHMETIC AND LOGIC UNIT
(ALU)
 Arithmetic and Logic Unit (ALU): The operation of
this component of a CPU is to conduct mathematical and
logical operations such as logical tests, comparisons,
addition, subtraction, etc. The programming scripts
containing these arithmetic and logical operations are
read and later dealt by this component of the Central
Processing Unit.

REGISTERS
 Registers: These are the memory locations of the CPU
itself. Registers are used to store data and instructions
read by the input devices. For fast data retrieval, these
are designed to get quick access.

CPU DEPENDENCY AND
PERFORMANCE
 Design of the CPU bus protocol
 Size and speed of the external buses
 Design of the CPU sub-architecture
 Clock rate of the CPU
 Number of available calculation unit

RANGE OF DIFFERENT
OPERATING SYSTEMS
 Real Time operating systems: The purpose of
developing and using real time OS is to simplify the
industrial operations.
 Single user multi-tasking operating system: These
systems are designed to perform specialised tasks by the
person keeping the expertise.

CONT.
 Single user multi tasking operating systems: This type
of operating system allows single user to perform
multiple tasks in the computer. They are mostly found on
the personal desktops
 Multi-user operating systems: This type of OS allows
multiple users to simultaneously use the computer
systems for their functions.

KEY FEATURES ASSOCIATED WITH THE
ARCHITECTURE OF AN OPERATING SYSTEM
 Hardware: All peripheral devices are there such a RAM,
HDD, CPU, etc.
 Kernel: It interacts directly with the hardware and
renders low level services.
 Shell: It is an interface to the kernel.
 Utilities: The functionalities of the operating system are
given by utilities.

KEY FEATURES ASSOCIATED WITH THE
ARCHITECTURE OF AN OPERATING SYSTEM
 Multi-user capabilities: There exist a capability of
Linux operating system where different computer
resources such as hard disks, memory, etc. can be
accessed by multiple users.
 Multi-tasking: Linus has calibre to manage more tasks
at a time. It helps in fostering the speed of the work. This
is performed by dividing the time of CPU wisely by the
execution of scheduling policies.

CONT.
 Portability: It is one of the major feature that made the
selected operating systems popular. Linux can operate on
different types of hardware in the same way.
 Security: For the confidential work, Linux operating
system is a reliable tool. In order to protect users from
unauthorised access of data and system, this operating
system renders security concepts.

SERVICES PROVIDED BY AN
OPERATING SYSTEM
 Program Execution: It controls various activities of
user programs top system programs such as printer, file
server, etc.
 I/O operations: An operating system, controls the
communication between the user and its devices. It reads
or writes operations with specific I/O devices.
 File system manipulation: The operation systems gives
the permission to the program for operation of a file. It
further renders interface to users to create/delete files
and directories.
 Communication: The major service of operation system
is handling routing and connection strategies.

CONT.
 Error detection: The operating system of a computer
consistently checks for the possible errors in the system.
Along with this, they take suitable actions to ensure
errorless computing.
 Resource allocation: While schedulers, all type of
resources are managed by the operating systems.
 Protection: OS manages all access to the system
resources. In addition to this, it ensure that the all
external I/O devices are protected from invalid access.

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