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CSC 203 – OPERATING SYSTEM (O/S) I – Overview of Operating
System
An operating system acts as an intermediary between the user of a computer and the
computer hardware. The purpose of an operating system is to provide an environment
in which a user can execute programs in a convenient and efficient manner.
An operating system is software that manages the computer hardware. The hardware
must provide appropriate mechanisms to ensure the correct operation of the computer
system and to prevent user programs from interfering with the proper operation of the
system.
Internally, operating systems vary greatly in their makeup, since they are organized
along many different lines. The design of a new operating system is a major task. It is
important that the goals of the system be well defined before the design begins. These
goals form the basis for choices among various algorithms and strategies.
Because an operating system is large and complex, it must be created piece by piece. Each of these pieces should be a well-delineated portion of the system, with carefully defined inputs, outputs, and functions. An operating system is a program that manages a computer’s hardware. It also provides a basis for application programs and acts as an intermediary between the computer user and the computer hardware. An amazing aspect of operating systems is how they vary in accomplishing these tasks. Mainframe operating systems are designed primarily to optimize utilization of hardware. Personal computer (PC) operating systems support complex games, business applications, etc. Operating systems for mobile computers provide an environment in which a user can easily interface with the computer to execute programs. Thus, some operating systems are designed to be convenient, others to be efficient, and others to be some combination CSC 203 - OPERATING SYSTEM (O/S) I - Overview of Operating System :
A better definition of it will be viewing it as the programs,
implemented in either software or firmware (microcode) that
makes the hardware useable. Hardware provides ‘raw computing
power’. Operating systems make this computing power
conveniently available to users – and they manage the hardware
carefully to achieve good performance.
Operating Systems are primarily resource managers, the main
resources they manage is computer hardware in the form of
processors, memory/storage, input/output devices,
communication devices and file/data.
However we choose to define them, operating systems are
integral part of the computing environment.
CSC 203 - OPERATING SYSTEM (O/S) I - DEFINITIONS CONTD :
An operating system, O/S, (executive, director, monitor, supervisor, etc) is an organized collection of programs and data that acts as an interface between machine hardware and users, providing the later with a set of facilities to simplify the design, coding, debugging and maintenance of user programs and at the same time controlling the allocation of resources to assure efficient operation. An operating system is basically the software that initiates and controls the interaction between the electronic and electromagnetic components of the computer so that they constitute a useful system for carrying out information processing as requested by the user. An operating system supervises all the activities taking place within the computer system. It can be thought of as an office manager who assigns work to different components of the computer system and who also helps out with more important and difficult task.
CSC 203 - OPERATING SYSTEM (O/S) I - DEFINITIONS CONTD :
CSC 203 - OPERATING SYSTEM (O/S) I - SYSTEM STRUCTURE:
We can also view a computer system as consisting of hardware/ software/ and data. The operating system provides the means for proper use of these resources in the operation of the computer system. An operating system is similar to a government. Like a government, it performs no useful function by itself. It simply provides an environment within which other programs can do useful work.
THE USER
The user's view of the computer varies according to the interface being used. Most computer users sit in front of a PC, consisting of a monitor/ keyboard/ mouse, and system unit. Such a system is designed for one user to monopolize its resources. The goal is to maximize the work (or play) that the user is performing. In this case, the operating system is designed mostly for a single-user with some attention paid to performance and none paid to various hardware and software resources being shared. Performance is, of course, important to the user; but such systems are optimized for the single-user experience rather than the requirements of multiple users. For mainframes or embedded systems, user experience may vary accordingly
A COMPUTER’S START UP SEQUENCE
First, some terms must be defined;
CPU
The CPU, or Central Processing Unit, is a large chip inside the
computer. This is the brains of the computer: it controls everything.
It works by reading instructions and data from RAM, performing an
instruction, and then writing the data back to RAM. Some of the
instructions may involve other components like the hard drive, but
the CPU is in control.
RAM
(Random Access Memory) temporarily stores data while the
computer is running.
- RAM is both readable and writable. You can add, change and delete
data stored in RAM.
- It is volatile. When the computer is switched off, all the data stored
in RAM is lost.
BIOS stands for Basic Input Output System. The BIOS is stored in
the ROM. It contains all the basic code for controlling your
computer hardware (such as keyboards, mice, monitors and hard
drives). After the startup sequence is complete, and control has
gone to the operating system, the BIOS does very little.
When you start up your computer, you may see a black screen displaying
“Press F2 for Setup”. This is the BIOS. By pressing F2, you enter a setup
screen where you can change where the BIOS loads the operating system
from.
The operating system is normally stored on the hard drive, but you can load
an operating system from a USB drive or a CD instead.
Startup sequence
So, how are these components used in the startup sequence?
- The CPU starts and fetches instructions into RAM from the BIOS,
which is stored in the ROM.
- The BIOS starts the monitor and keyboard, and does some basic
checks to make sure the computer is working properly. For
example, it will look for the RAM.
- The BIOS then starts the boot sequence. It will look for the
operating system.
- If you don’t change any of the settings, the BIOS will fetch the
operating system from the hard drive and load it into the RAM.
- The BIOS then transfers control to the operating system.
What is an HDD?
An HDD is a data storage device that lives inside the computer. It has
spinning disks inside where data is stored magnetically. The HDD has
an arm with several "heads" (transducers) that read and write data on
the disk. It is similar to how a turntable record player works, with an LP
record (hard disk) and a needle on an arm (transducers). The arm
moves the heads across the surface of the disk to access different data.
HDDs are considered a legacy technology, meaning they’ve been
around longer than SSDs. In general, they are lower in cost and are
practical for storing years of photos and videos or business files. They
are available in two common form factors: 2.5 inch (commonly used in
What is an SSD? SSDs got their name—solid state—because they have no moving parts. In an SSD, all data is stored in integrated circuits. This difference from HDDs has a lot of implications, especially in size and performance. Without the need for a spinning disk, SSDs can go down to the shape and size of a stick of gum (what’s known as the M.2 form factor) or even as small as a postage stamp. Their capacity—or how much data they can hold—varies, making them flexible for smaller devices, such as slim laptops, convertibles, or 2 in 1s. And SSDs dramatically reduce access time since users don’t have to wait for platter rotation to start up. SSDs are more expensive than HDDs per amount of storage (in gigabytes, or GB, and terabytes, or TB), but the gap is closing as SSD prices begin to drop. What makes SSDs an increasingly popular choice is their speed. Across the board, SSDs outpace HDDs because they use electrical circuitry and have no physical moving parts. This leads to shorter wait times when you’re starting up and fewer delays when opening apps or doing heavy computing tasks
Each processor is constituted of one or more individual processing units called “cores”. Each core processes instructions from a single computing task at a certain speed, defined as “clock speed” and measured in gigahertz (GHz). Since increasing clock speed beyond a certain point became technically too difficult, modern computers now have several processor cores (dual- core, quad-core, etc.). They work together to process instructions and complete multiple tasks at the same time. Modern desktop and laptop computers now have a separate processor to handle graphic rendering and send output to the display monitor device. Since this processor, the GPU, is specifically designed for this task, computers can handle all applications that are especially graphic-intensive such as video games more efficiently. In the early 2000s, as processor clock speeds began plateauing, CPU manufacturers needed to find other ways to increase processing performance. Initially, they achieved this by putting multiple processors in high-end computers. While this was effective, it added significant cost to the computers and the multiprocessing performance was limited by the bus speed between the CPUs. By combining processors on a single chip, CPU manufacturers were able to increase performance more efficiently at a lower cost.
A CORE:
or CPU core, is the "brain" of a CPU. It receives instructions, and performs calculations, or operations, to satisfy those instructions. A CPU can have multiple cores. A processor with two cores is called a dual-core processor; with four cores, a quad-core; six cores, hexa-core; eight cores, octa-core. As of 2019, the majority of consumer CPUs feature between two and twelve cores. Workstation and server CPUs may feature as many as 48. Each core of a CPU can perform operations separately from the others. Or, multiple cores may work together to perform parallel operations on a shared set of data in the CPU's memory cache. There are two major manufacturers of computer processors, Intel and AMD
