Computer Basics
Basic Computer Knowledge
Types of Computers
Size/Capacity
Supercomputer
Mainframe
Mini computer
Micro computer (PC)
Data Processing
Analog Computer
Digital Computer
Hybrid Computer
Generation
1st
2nd
3rd
4th
5th
Purpose
General purpose
Special purpose
Computer Software
System software
Operating System
Manages computer resources hardware, software, applications etc.
Device drivers
Operates certain devices. e.g. device driver for printer
Utility software
Maintains computer system. e.g. Antivirus, disk cleaners etc.
Application software
Software performing special tasks. e.g. Microsoft word, Excel etc.
Computer Hardware
Computer case – Outer covering that protects (mostly for desktops). Keeps computer cool
Power Supply Unit – Converts alternating current to direct current. Controls voltage
Internal devices – Central processing unit(CPU), Read-only memory (ROM), Random Access memory (RAM), Graphic cards, buses etc.
Input devices – Keyboard, mouse, touchpad, trackball, microphone, cameras, scanners etc.
Output devices – Monitors, printers, speakers, headphones etc.
Storage devices – Hard disk drives, CDs, DVDs, USBs etc
Computer Memory – Primary
Non-Volatile Primary memory
Read-Only memory – Data cannot be modified after manufacture
Programmable read-only memory (PROM) – Content can be changed
Erasable programmable read-only memory (EPROM) – can be re-programmed by removing chips
Electrically erasable programmable read-only memory (EEPROM) – can be electrically erased and re-programmed without removing chips
Volatile Primary memory
Static RAM – Data is retained as long as it has power. It is faster
Dynamic RAM – Used for processing of data and program code. This is main memory
Computer Memory – Secondary
Fixed Storage Secondary memory
HDD (Hard disk drive) – based on read/write head and spinning discs. Magnetic storage
SSD (Solid-state drive) – has no moving parts. Faster and more reliable
Removable Storage Secondary memory
Optical discs – CDs, DVDs etc.
Memory cards – Used in mobile phones, laptops, cameras etc.
USB flash drives
Floppy discs – Outdated
Cache memory – temporarily stores frequently used data and instructions for quick processing by CPU.
| Unit | Measurement |
|---|---|
| 1 nibble | 4 bits |
| 1 byte | 8 bits or 2 nibbles |
| 1 kilobyte | 1024 bytes |
| 1 megabyte | 1024 kilobytes |
| 1 gigabyte | 1024 megabytes |
| 1 terabyte | 1024 gigabytes |
| 1 petabyte | 1024 terabytes |
| 1 exabyte | 1024 petabytes |
| 1 zettabyte | 1024 exabytes |
| 1 yottabyte | 1024 zettabytes |
CPU (Central Processing Unit)
Executes the instructions given by a computer program. It has Arithmetic Logic Unit, Control Unit and Registers
Arithmetic Logic Unit (ALU)
It will perform the Arithmetic and Logic operations
Control Unit (CU)
CPU instruction cycle is managed by Control Unit
Registers
used for accessing and storing data required
The CPU instruction cycle is synchronized by CPU clock
Types of CPU
Single-core CPU
Can execute one command at a time
Not good for multi-tasking
Dual-core CPU
Acts like 2 CPUs
Can execute more than one command at a time
Multi-tasking is possible
Quad-core CPU
4 cores working simultaneously
More multi-tasking capabilities than dual-core CPU
Similarly hexa-core, octa-core and deca-core CPUs are powerful than Quad-core
History of CPU
Vacuum tubes – First Generation – 1940s and 1950s
Transistors – Second Generation – 1950s and 1960s
Integrated Circuits (Ics) – Third Generation – 1960s and 1970s
Microprocessors – Fourth Generation – 1970s to Present
Artificial Intelligence – Fifth Generation – Present and Future
Operating System – It is system software that manages resources (hardware, software and applications) of computer
Functions of Operating System
Process management – Manages multiple processes allocating CPU
Memory management – Allocates memory between processes
Security management – It sees that only authorized users can access the applications
Storage management – Manages storage resources
Resource management – Dynamically allocates resources between processes
Types of Operating System
Real-time operating system – The response time is very quick
Time-sharing operating system – Multiple tasks get equal opportunity and each user gets CPU time as if using a single system
Batch operating system – The operator groups similar jobs into batches and sent to the computer
Distributed operating system – various computers which are connected communicate with each other
Networking operating system – Many clients are connected to the server and share resources over a private network
A computer network is two or more computing devices connected sharing resources among them
Types of networks based on Area
Personal Area network (PAN) – connects personal use devices within a range of about 30 feet
Local area network (LAN) – connects devices within a range of about 1 km
Metropolitan area network (MAN) – connects devices within a range of about 40 km
Wide area network (WAN) – connects devices across countries or continents
Network topology is the way the components are arranged in the network
Types of network topologies
Bus topology – All the devices are connected to a single communication line
Ring topology – Each node is connected to two other nodes forming ring shape
Star topology – All hosts are connected to a central node
Full mesh topology – each node is connected to every other node
Partial mesh topology – not all nodes are interconnected
Tree topology – all nodes are connected to a root node forming a tree structure
Network Devices
Routers – router analyses the data packet received and transmits it to the destination
Modems (Modulator demodulator)
The modem that is sending data converts the digital data to analog signals and it is called modulator. The modem that is receiving data converts the analog signals to digital data and it is called the demodulator
Repeater – regenerates the signal received and reduces noise
Hub – Connects multiple networks and sends data packets to all devices
Gateway – used to communicate between different networks which may even have different protocols
Bridge – connects multiple network segments. It has single input and single output
Switch – connects multiple hosts. It uses MAC addresses and sends data to the port connected to the device
MAC (Media Access Control) Address
It is a unique address assigned to network interface controller (NIC)
Assigned by manufacturer and therefore is permanent address
It is a 48-bit hexadecimal address. e.g. 00:F6:F7:00:AE:5C
The first 3 bytes are called Organizationally Unique Identifier (OUI)
IP (Internet protocol) Address
Identifies a device on the network
IP addresses are dynamic as nodes may get removed or added to the network
IPV6 address is 128-bit represented by 8 groups of hexadecimal numbers separated by colons
IPv4 address is 32-bit represented by 4 groups of decimal numbers separated by colons
Domain Name System
It is a hierarchical naming system for resources (computers etc.) on internet
It is the system that identifies the resources on internet or internet protocol networks. The domain name can be mapped to the IP address of the resource
It has Domain Name Server which converts the domain name to its corresponding IP address
The Domain Name Server has a database of domain names and the corresponding IP addresses
Computer network models
OSI (Open System interconnection) model
Application layer
Presentation layer
Session layer
Transport layer
Network layer
Data link layer
Physical layer
Internet model (TCP/IP)
Application layer
Transport layer
Internet layer
Network Access layer
Encoding is converting characters (letters, numbers etc) to special format
Types of encoding schemes
ASCII (American Standard Code for Information Interchange)
It is a 7-bit code to represent character. There are 128 characters (0 to 127)
Unicode
It is a universal character set covering all languages
It uses 8 bit (utf-8), 16 bit (utf-16), and 32 bit (utf-32) encoding
ISCII (Indian Script code for Information Interchange)
It is an 8-bit code that represents Indian languages
0 to 127 are Ascii codes and 128 to 255 are characters of Indian languages
Number System
It is a method to write numbers
The number of unique characters in a number system is called the base of the number system or the radix. E.g. In binary system there are 2 unique characters 0 and 1
Types of Number System
Decimal number system – Numbers 0 to 9 are used. It is called base-10 system
Binary number system -It has 2 digits 0 and 1. It is called base-2 system
Octal number system – Numbers 0 to 7 are used. It is called base-8 system
Hexadecimal number system – Numbers 0 to 9 and alphabets A to F are used. It is called base-16 system
Future IT Trends
Artificial intelligence – It is described as thinking and acting rationally. It is the ability to take actions that maximize the chance of success
Big Data – It is the data that is large and complex. Some of the sources of big data are emails, WhatsApp messages, YouTube data, Instagram data etc.
Cloud Computing – makes available computer system resources on-demand. Available over the internet on pay-as-you-go basis. The services are infrastructure as a service (IaaS), platform as a service (PaaS) and software as a service (SaaS)
Internet of Things (IOT) – is the concept of connecting devices and exchange of data between them over any communication network including internet
Blockchain – It is a shared and decentralized database with digital ledger having records called “blocks”. All the computers have a copy of the database. Example is digital currency, prominently cryptocurrency