Operating System, Database and Programming Basics Notes

Operating system, database and programming basics form the core of the Computer Knowledge section in SSC, banking, railways, defence and state examinations. These topics are conceptual, and questions are usually asked on definitions, types, examples and differences. A student who understands what an operating system does, how a database stores data and how a program is translated and run can answer almost all such questions. This note explains the three topics in simple language with tables, examples and quick-revision points.

Part 1: Operating System (OS)

An operating system is the system software that manages the hardware and software resources of a computer and acts as a bridge between the user and the hardware. Without an operating system, a computer cannot run any application. When you switch on the computer, the BIOS starts first, checks the hardware and then loads the operating system into RAM; this process is called booting. A cold boot starts the computer from the power-off state, and a warm boot restarts it without switching off the power.

Functions of an Operating System

• Process management: It decides which program gets the CPU and for how long.
• Memory management: It allots and frees RAM for programs.
• File management: It creates, stores, names, searches and protects files and folders.
• Device management: It controls input and output devices using device drivers.
• Security: It protects the data through passwords and user accounts.
• User interface: It gives a command line or a graphical interface for the user.

Types of Operating Systems

Popular operating systems include Windows by Microsoft, macOS by Apple, Linux (free and open source, created by Linus Torvalds in 1991), Unix, Android by Google and iOS by Apple. In India, BOSS (Bharat Operating System Solutions) is a Linux-based system developed by C-DAC. The user interface can be a CLI (command line interface), where commands are typed, as in MS-DOS, or a GUI (graphical user interface), where icons, windows and menus are used, as in Windows. A kernel is the core of the OS that talks directly to the hardware, and a shell is the layer that takes the commands of the user. A device driver is a small program that lets the OS work with a device such as a printer.

Part 2: Database

A database is an organised collection of related data stored in such a way that it can be easily accessed, managed and updated. The software used to create and manage a database is called a Database Management System (DBMS). Examples of DBMS software are MySQL, Oracle, Microsoft Access and SQL Server. A school database that stores the names, roll numbers and marks of students is a simple example.

Important Database Terms

Types of Database Models and the Language SQL

The main database models are the hierarchical model (tree-like structure), the network model, and the relational model, which stores data in tables and is the most popular. A DBMS based on the relational model is called an RDBMS, and it was proposed by E. F. Codd in 1970. The language used to work with a relational database is SQL (Structured Query Language). Important SQL commands are SELECT (to read data), INSERT (to add data), UPDATE (to change data), DELETE (to remove data), CREATE (to make a table) and DROP (to delete a table). The advantages of a DBMS are less data duplication (redundancy), better security, data consistency, easy sharing of data and quick searching. Normalisation is the process of organising data to reduce redundancy.

Part 3: Programming Basics

A computer understands only machine language made of 0 and 1. A program is a set of instructions written in a programming language to perform a task. A person who writes programs is called a programmer, and a step-by-step method to solve a problem is called an algorithm. A flowchart is the diagram of an algorithm, which uses symbols: an oval for start or stop, a rectangle for a process, a parallelogram for input or output, a diamond for a decision and arrows for the flow.

Levels of Programming Languages

Translators: Compiler, Interpreter and Assembler

A translator is a program that converts a program from one language to another. An assembler converts assembly language into machine language. A compiler translates the whole high-level program into machine code at once, and it shows all the errors after compiling; the program then runs fast. An interpreter translates and runs the program line by line, and it stops at the first error, so it is easier for debugging but slower in running. C and C++ use compilers; Python and BASIC commonly use interpreters. Java uses both: it is compiled into bytecode and run by the Java Virtual Machine.

Types of Errors and Other Terms

• Syntax error: A mistake in the grammar of the language, such as a missing bracket.
• Logical error: The program runs but gives a wrong result because of wrong logic.
• Runtime error: An error that occurs while the program is running, such as division by zero.
• Debugging: The process of finding and removing errors (bugs) from a program.
• Source code is the program written by the programmer, and object code is the machine code produced by the compiler.
• Object-oriented languages such as C++, Java and Python organise code into objects and classes.

Differences That Are Often Asked

A compiler checks the whole program and then runs it, while an interpreter runs the program line by line. A DBMS stores data in any form, but an RDBMS stores data in related tables. Low-level languages are machine dependent and fast, while high-level languages are machine independent and easy to write. System software, such as an operating system, runs the computer, while application software, such as a word processor, helps the user to do a task. Kernel is the inner core of an OS, while shell is the outer layer used by the user. If you remember these contrasts as pairs, you can easily eliminate the wrong options in objective questions.

Practice Questions With Answers

(1) The process of starting a computer is called booting. (2) Linux was created by Linus Torvalds. (3) The core of an operating system is the kernel. (4) A field that uniquely identifies a record is a primary key. (5) The language used to manage relational databases is SQL. (6) The translator that converts the full program at once is a compiler. (7) Finding and removing errors in a program is called debugging. (8) A rectangle in a flowchart shows a process.

Quick Revision

• OS manages hardware, memory, files, devices and security; Windows, Linux, Android and iOS are examples.
• Database: field is a column, record is a row, primary key is a unique identifier.
• RDBMS uses tables and SQL; the relational model was proposed by E. F. Codd.
• Machine language is the only language directly understood by the CPU.
• Compiler translates all at once; interpreter translates line by line.

Revise these definitions and the tables regularly, and use real examples from your phone and computer to make the concepts clear.

Related Notes to Read Next

Continue your preparation with these related notes from the same subject:

• History and Generations of Computers
• Types of Computers and Supercomputers in India
• Computer Memory Notes: RAM, ROM, Cache
• All Computer Knowledge notes

Frequently Asked Questions (FAQ)

What is an operating system?

An operating system is the system software that manages the hardware and software resources of a computer and works as a bridge between the user and the hardware.

What are the main functions of an operating system?

The main functions are process management, memory management, file management, device management, security and giving a user interface.

What is booting?

Booting is the process of starting a computer, in which the BIOS checks the hardware and loads the operating system into RAM.

What is the difference between CLI and GUI?

A CLI needs typed commands, as in MS-DOS, while a GUI uses icons, windows and menus, as in Windows.

What is a kernel?

The kernel is the core part of the operating system that communicates directly with the hardware.

What is a database and a DBMS?

A database is an organised collection of related data, and a DBMS is the software that creates and manages it, such as MySQL or Oracle.

What is the difference between a field and a record?

A field is a single piece of data and a column of the table, and a record is a group of related fields and a row of the table.

What is a primary key?

A primary key is a field that uniquely identifies each record in a table, and it cannot be repeated or left empty.

What is SQL?

SQL stands for Structured Query Language and it is used to create, read, update and delete data in a relational database.

What is the difference between a compiler and an interpreter?

A compiler translates the whole program at once and then runs it, while an interpreter translates and runs it line by line.

Which language does the computer understand directly?

The computer understands only machine language, which is made of binary digits 0 and 1.

What is the difference between syntax error and logical error?

A syntax error is a mistake in the grammar of the language and stops the program, while a logical error lets the program run but gives a wrong result.