A Computer is an electronic device thal takes data as input, processes it according to the given intructions and produces the result (Information)
Data - Raw Facts and figures.
It consist of Hardware and software -components that work together to perform various task and provide usefull services to the user.
Components of a Computer:
1. Input Device: The Input unit consist of all the Input devices attach to the computer. It converts the data that is entered by the user to binary form so that the computer can understand from it. eg- Keyboard, Mouse Scanner etc.
2. CPU : The CPU takes the instructions from the memory Decodes them, executes them and stores or display the result. CPU Consists of three main parts.
i) ALU (Arithmetic and logic unit):- It performs all arithmetic operations (+,-* /) and logical operation (<,><=,<=,>=)
ii) Cu: Control Unit:- Itmanages and coordinates all activities of the computer. It Controlls the flow of data between CPU memony and I/O devices.
iii) Memory Unit: It is used to store data and instructions temporarily during processing, there are three types of Memony,
a.) Primary Memony.
b.) Secondary Memory
c.) Cache Memory.
3.) Output Unit: The Output unit consist of all the output devices attach to tinath computer. It converts the binary data coming from the CPU to human understandable form. eg Monitor, Printer, speaker etc.
Q) What is Software and Hardware?
Charateristics of a Computer:-
i) Speed: It can perform millions of calculations per second. The computation speed is very fast
ii) Accuracy:- Since Computers operate in pre programme softwar there is no chance of human error.
iii) Diligence: They can perform complex and long calculations at the same time with the same accuracy.
iv) Versatility: These are versatile as they can do multiple tasks at the same time.
5. Storage :- It can store a large amounts of data or instructions which can be retrieved at any point of time.
Types of Memory.
Primary Memory
RAM
SRAM
DRAM
ROM
MROM (Masked ROM)
PROM (Programmable ROM)
EPROM (Erasable Programmable ROM)
EEPROM (Electrically Erasable PROM)
Secondary Memory
Cache Memory
8 bits = 1. Byte
1024 Bytes 1 KB
1024 KB = 1 MB
1024 MB = 1 GB
1024 GB-1TB
Primary Memory: (Main Memory). It is used to store data and programmes during computer execution. It is of two types RAM and ROM.
RAM (Random Access Memory) Volatile memory) - It stores information temporarily till the power supply is on. All the data and programmes that are currently executed uses RAM as It is the working memory of the computer It is of two types Static RAM and Dynamic RAM
Static RAM:- It uses transistors that are capable of retaining information as long as the power of supply is on. It's faster.
Dynamic RAM:- It uses capacitors and transistors and stores the data as a charge on the capacitors. It needs refreshing of charge on capacitors after some milliseconds to retain that data. It is slower.
ROM:-- (Read Only Memory Non- Volatile Memory) It stores data parmanently. Even when there is no power supply. It is used to store essential programmes that are used to start (boot) the computer. We cannot modify the ROM. It can only be read and cannot write anything in it.
M R O M (Masked ROM) these are pre-programmed during their manufacturing and cannot be modified.
PROM:- Programmable read only memory. It is modifiable only once the user purchases the blank PROM and uses the PROM program to put the required contents into the plum it cannot be erased.
EPROM :- ERASABLE PROGRAMMABLE READ ONLY MEMORY:- is an extension of PROGRAMMABLE READ ONLY MEMORY where it can erase the whole contents of ROM by UV Rays.
EEPROM :- electrically erasable Programmable with early memory , the contents can be selectively erased electrically and can be reprogrammed multiple Times.
Secondary memory auxiliary or backup memory:- it is a non volatile memory used to store large amounts of data a CPU cannot directly access the content of secondary memory. The data is first transferred into primary memory from where the CPU can access it it is lower than primary memory but it is cost effective it is used for long term data storage for example HDD, Flash Drive , DVD, CD, etc.
Cache memory:- it is a very high speed semiconductor memory used to store frequently used data and instructions it helps the CPU improve its performance. It acts as a buffer between the CPU and the main memory extra space . The access time is less and its speed is very high and faster than primary memory. Its sizes are small and very expensive.
Operating system:- an operating system is an interface between the user and the computer it is a set of programs that control coordinates and supervises the activities of the computer hardware and software each computer must have at least one operating system.
The functions of operating systems
1. Memory management :- operating keeps track of primary memory it decides which process will get the memory and for how much time it allocate the memory to a process where it needs it and deallocates it when the process is terminated.
2. Processor management:- the operating system keeps track after the processor and the status of the process decides which processor will get the processor and how much time. It allocates the processor to a process and deallocates the processor when the processor is no longer required.
3. Device Management:- An OS manages device communication between the I/O devices via their respective driver. it tracks all the devices and decides which process gets the device when and for how much time.
4. file management:- A file is a logical collection of related information stored in the memory of secondary storage. The operating system managers files folders and directory system in a computer. It keep tracks of information location uses status etc.
5. Security:- the operating system has a number of built in tools to protect computers against security threads including the antivirus software and setting after firewall to block suspicious network activity by the use of login ID and password it prevents unauthorised to programs and data.
Type of operating system
1. Real time operating system:- its mean objective is to provide a quick response time to meet a scheduling deadline of events. It reacts to inputs and responds to them quickly. These types of operating systems are used when the time requirement is very strict like missile system flight control system robots etc.
2. Single user single tasking operating system:- in this a single user can perform single task at a time functions like printing a document downloading images can be done one at a time for example MS dos
Advantages:- consume very less memory and simple
Disadvantages:- one task in one time
3. Single user multiple tasking operating system:- here a single person can do multiple task at the same time for example a user can work on a word document and can browse Internet simultaneously for example MS windows Mac operating System.
Advantages:- it is time saving as this can do multiple task and give high productivity.
Disadvantages:- the operating system is very highly complex and occupies more memory space.
4. Multiple User Multi tasking operating system:- share multiple user access the computer at the same time. The operating system manages the memory and the resources among the various users according to requirement. The task of one user will not affect the task of another user.
For example Unix and Linux
Various popular operating system
1. MS Dos:- develop in 1981 it was a non graphical command line operating system the operating system use a command line interface for the user to input commands to navigate open and manipulate the files on their computer.
It got enormous popularity in 1980's but the technology did not keep pace. With the competition as it was a single user single tasking operating system. It lacked the multi user multitasking capability of the Unix operating system and the user friendly graphical user interface GUI of the early Mac computers.
2. Windows operating system:- developed in 1985 by Microsoft corporation it provides an interface known GUI who eliminates the need to memorize the commands and we can navigate the mouse to dialogue boxes button tabs and icons using a mouse it also provides multi-tasking capability.
Unix/Linux OS:- Unix is a multi user multitasking proprietary software . (To buy) Develop in 1960's initially it was command line later on GUI was introduced
Linux is an open source Unix based operating system developed in 1991. Linux uses Boss command line interface and graphical future interface
Advantages of Linux--
Free of cost
Highly secure system
Mac operating system:- developed in 1984 it is a proprietary (to buy) graphical operating system developed by apple.
Advantages
Better security
Comparatively faster
Smooth and light weight
Easy to use
Disadvantages
Very expensive
File system in operating system:- file system provides a structured way to store organised manage data or storage devices such as hard drive SSD and USB devices. It tells us how the data is permanently stored and fetched.
Operative done by the file system
To create a file:- file attributes (meta data):-
Name
Extension
Identifier
Location
Size
Modified data created data
Protection or permission
Encryption or compression.
A file mein contains text source code executable instructions photographs database audio video or other forms of digital data. The operating system maintains information about this files and coordinates requests made by applications so that the data can be stored are retrieved correctly.
Operation stand by the file system
1. Create:- the create operations establishes a new file. The operating system records file information and prepares the required structure so that the data can later be stored in the file. The information are called file attributes or method data
Here are some attributes and their purposes
File name:- it identifies the file to users and applications for example student.pdf
File type:- it indicates the nature or format of the store data for example.txt, .pdf .jpg
File size:- indicates the number of storage occupied. For example one megabyte
Location:- it provides information needed to locate the file
Protection:- if defines permitted access to the file for example read only or write only file
Time:- it records events such as creation date modified date etc.
Owner:- it identifies the user or account associated with that file
ii. Open operation:- before the file operations can be performed an application of the operating system can open the file.
iii. Read operation:- the read operation leads the application to read the existing file data
iv. Write operation:- write operation places New operation into a file or changes existing information into a file
v. Reposition:- an application may need to move its current position within a file this allows it to access a particular person of the data without necessary processing everything from the beginning.
vi) close:- an application can close the file after completing its work.
vii) rename:- it changes the logical name of a file while retaining its stored data.
Popular file system
I) FAT:- file allocation table it is an older file system used by older versions of windows and other OS.
ii) NTFS :- new technology file system is a modern file system used by windows that supports features like file permissions encryption and compression.
iii) EXT:- extended file system is used by Linux and Unix based operating system
iv) HFS:- HIERARCHICAL FILE SYSTEM. It is used by the Mac operating System.
V. APFS:- Apple file system. It is a new file system introduced by Apple for their Mac and IOS devices
File access method
1. Sequential access:- the file records are accessed one after another in a strict and linear order for example magnetic tapes which are easy to implement but slow when searching for random data.
2. Direct access:- random access files are accessed in random order using a specific block number for example database large data sets etc. its retrieval time is fast but more complex to manage at programs.
Internet is an interconnected network of computers used to exchange information all over the world.
History of internet:-
ARPANET:- ADVANCE RESEARCH PROJECT AGENCY NETWORK, it was developed in 1969 by the United State defence department for military communication.
In 1983 TCP/IP became the connection by which communication was done between different networks.
In 1991 Tift Burnerslee develop worldwide web making the internet available for the general public.
In the 2000 rise of broadband and wireless communication.
In 2020 onwards 5G and iot devices
How internet works
To connect computers n*( n - 1) / 2 wires are required so we use routers. Routers are networking hardware device that forward data packets between different computer networks. Routers can connect up to 10 computers so far millions of routers are connected to each other.
DNS:- domain name server. It acts like a phone book on the internet. It translates human readable domain names www.google.com into numerical IP addresses 8.8.8.8 that computers used to locate each other on the network.
ISP:- internet service providers are organisations that provide services related to accessing and using the internet for example BSNL Airtel jio etc.
Server:- it is a computer hardware or software system that provides data resources services or programs to other computers known as clients of a network.
Data centre:- these dedicated physical building that was computer system servers, there are storage drive and networking hardware to store process and distribute Digital information.
It is used to protocol http and https
Advantages of internet
Social networking
Education and technology
Entertainment
Online services like banking ticket booking shopping etc
Disadvantages of the internet
Thread to Personal information.
Unwanted emails in bulk known as spam
cyber crime
Virus attack
Web browsing
It is an application software used to explore the world wide web it is installed in the client computer and it requests information from the web browser.
Web browsing is the process of accessing and navigating the internet using a web browser which retrieves and displays we have content to the browser.
How does the web browser work
When we enter the URL uniform resource locator the browser contacts the DNS to translate the domain name into an IP address and then sends a request to the web server with the IP address for the web page.
The web server processes the request and send back the required web page to the web browser which renders it into a visual format for the user.
Their instruction follows a client server model where the browser acts as a client requesting information from the server. The protocol used in this introduction is called http or https.
Some popular web browsers
Google Chrome is developed by Google. It is one of the most widely used web browsers known for its speed and simplicity.
Microsoft edge developed by Microsoft it is the default browser on windows 10
Mozilla Firefox is developed by Mozilla. It is an open source browser known for its privacy and customisation of its options.
Apple Safari is developed by Apple. It is the default browser on Mac and IOS devices and it is known for its speed and integration with other Apple products.
Brave is developed by brave software it is famous for privacy and security it blocks third party ads and trackers by default.
Opera is developed by Opera software it is known for its speed and built in VPN virtual private network feature
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