Computer Systems Architecture and Operating Systems - BTEC HND Report

This report provides a detailed overview of computer systems architecture, covering the main subsystems such as the Central Processing Unit (CPU), storage unit, and I/O devices, as well as their organization and connections. It explains the purpose and operation of the CPU, including its components like the Arithmetic Logic Unit (ALU), Control Unit (CU), and registers, and discusses factors affecting CPU performance. The report also explores different types of operating systems, including real-time, single-user multi-tasking, and multi-user systems, highlighting key architectural features such as hardware, kernel, shell, and utilities. Furthermore, it outlines the services provided by an operating system, including program execution, I/O operations, file system manipulation, communication, error detection, resource allocation, and protection mechanisms. The document concludes with a list of references used in compiling the report.

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.