Computer Generations: A Brief Overview

Storage Devices

• A hard disk consists of a spindle, platters made of non-magnetic material, and two surfaces coated with magnetic material.
• Each surface has serially numbered tracks and sectors or blocks.
• Hard disks rotate at speeds of 5400 and 7200 rpm.

Magnetic Tape

• Magnetic tape is made of plastic film coated with magnetic material on one side.
• It can store up to 1 TB or more, but 200 TB is expected.
• However, it is not fully portable and requires a separate tape drive.
• Data is accessed sequentially, making it unsuitable for backup.

Optical Disks

• Optical disks, such as CD-ROM, DVD-ROM, and Blu-ray disks, are non-volatile read-only memory.
• CD-ROM and DVD-ROM can hold large volumes of data (700MB to 8.5 GB).
• Blu-ray disks have a capacity of up to 50 GB.
• A laser beam is used to control read and write operations, constructing pits and lands by burning selected areas along tracks.

Flash Memory

• Flash memory does not have moving parts and is based on EEPROM.
• It is available in various forms, such as pen drives, magnetic cards (SD cards), and solid-state disks (SSDs).
• Flash memory is portable, requires little power, and is reliable.

Networks

• The internet is a wide network of computers, open to all, and contains a large number of intranets.
• Connecting computers in a network requires additional devices, such as hubs and switches, which are not part of the computer's basic configuration.

Network Hardware

• Hubs accept network data from computers and broadcast it to nodes by checking the destination address.
• Switches have a table containing MAC addresses of connected devices and send data after looking up the table for the destination.
• Bridges connect two networks using the same protocol, while routers connect two similar or dissimilar networks separated by a long distance.

Software Basics

• Software is a collection of code that drives a computer to perform related tasks.
• Programs in software use a language, and the source code is created by programmers using programming languages like C, C++, Java, and Python.
• Software is developed to operate on multiple platforms.

Software Types

• Computer software can be broadly classified into two types: system software and application software.

Computer Generations

• The second generation computers used magnetic hard disks for secondary memory.
• The third generation computers had OS and could run programs invoked by multiple users.
• The fourth generation computers used microprocessors, LSI, and VLSI, and had OS moved from MSDOS to GUI like Windows.
• The fifth generation computers use artificial intelligence, natural languages, and are expected to interact with users in natural language.

Computer Types

• Supercomputers are huge machines with the most powerful and fastest processors, using multiple CPUs for parallel data processing.
• They have speeds measured in flops (floating point operations per second), with the fastest operating at 34 petaflops.

Cache Memory

• Cache memory holds frequently used program portions, acting as a buffer between CPU and RAM.
• It has multiple levels: L1 (smallest and fastest), L2 (present closer to CPU), and L3 (shared by cores).

Registers

• Registers are small, ultra-fast memory integrated into the CPU, representing the fastest memory of the computer.
• Each register has a length equal to the computer's word length.
• Data is loaded into registers before processing, and registers are numbered and specified by program instructions.

Secondary Memory

• Secondary memory is not directly connected to CPU and exists inside and outside the machine.
• It is non-volatile, offline, and long-term storage, slower, and cheaper than primary memory but has higher capacity.

Hard Disk

• Hard disk is the oldest secondary storage device, with more capacity and less cost.
• It is commonly present in laptops with 500GB and desktops with 1TB.

Enumerations

• An enumeration is a list of constant integer values, with distinct names.
• The keyword used is "enum", and enumeration constants are used in programming.

Strings

• A string is a group of characters together, enclosed within double quotes.
• Strings end with a NULL character (\0), and are used in programming.

Operators

• Operators are symbols that tell the compiler to perform specific mathematical and logical functions.
• The different operators supported in 'C' are: arithmetic, relational, logical, assignment, bitwise, unary, and ternary/conditional operators.

Arithmetic Operators

• Arithmetic operators perform mathematical operations, such as addition, subtraction, multiplication, division, and modulus.

Relational Operators

• Relational operators are used to compare two quantities, producing an output of either 0 (False) or 1 (True).