CBSE Class 11 Informatics Practices

Chapters: 4

1. Introduction to Computer System

Computers and computing · Computer memory · Software

Basic Computer Organisation – A computer system has hardware (parts you can touch) and software (instructions). Input devices bring data in, the CPU (ALU + Control Unit + registers) processes it, and output devices give results. Memory forms a ladder: registers and cache are tiny and fastest, primary memory (RAM, ROM) holds running programs, and secondary storage (HDD, SSD, pen drive) keeps data permanently. Memory is measured in bits and bytes: 8 bits = 1 byte, and each bigger unit (KB, MB, GB, TB, PB) is 1024 times the one before.
Computers and Computing: Evolution, Parts and I/O Devices – A computer is an electronic machine that takes input, processes it under the control of a program, stores data and gives output. Computing devices grew from the abacus to smartphones. Every computer has an input unit, a CPU, memory and an output unit, joined by buses and ports.
Computer Memory: Units, Primary and Secondary, Data Recovery – Computers store everything as bits (0 or 1). 8 bits make a byte, and each bigger unit is 1024 times the one before. Primary memory (RAM, ROM, cache) works directly with the CPU; secondary storage (HDD, SSD, pen drive) keeps files for a long time. A deleted file can often be recovered until it is overwritten, so data must be protected.
Software: System and Application, Generic and Specific – Software is a set of programs. System software (operating system, device drivers, utilities, language translators) runs and looks after the computer. Application software does a user's task. Application software can be generic (general-purpose, ready-made for many users) or specific-purpose (customised for one organisation's need).
Types of Software – Software is of two big kinds. System software runs the computer: the operating system, utility programs (antivirus, disk cleanup, backup, compression) and device drivers. Language translators are also system software: an assembler turns assembly language into machine code, a compiler translates a whole high-level program at once, and an interpreter translates and runs it line by line. Application software does a user's job: general-purpose (word processor, spreadsheet, browser) or customised (made for one organisation).

2. Introduction to Python

Python basics · Control statements · Lists · Dictionaries · Introduction to NumPy

Python Basics: Modes, Variables, Data Types and Operators – Python runs in interactive mode (one line at a time) or script mode (a saved .py file). Blocks are shown by indentation. Variables are names tied to values; every value has a data type, and some types are mutable. Operators build expressions that Python works out by precedence. input() reads text, int()/float()/str() convert types, and debugging fixes syntax, runtime and logical errors.
Getting Started with Python – Python is a high-level, free and open-source, interpreted, portable, case-sensitive language that is easy to read. You can run it in interactive mode (type after the >>> prompt and see the result at once) or script mode (save code in a .py file and run it). Python's character set includes letters, digits, special symbols, whitespace and all Unicode characters. The smallest units of a program are tokens: keywords, identifiers, literals, operators and punctuators. A variable is a name that refers to a value; in an assignment the right side (r-value) is evaluated first and stored in the left side (l-value). Comments start with # and are ignored by Python.
Flow of Control in Python – Flow of control is the order in which statements run. Python has three kinds: sequential (top to bottom), selection (if, if-else, if-elif-else) and repetition (for and while loops). Blocks are marked by indentation (usually 4 spaces after a colon). range(start, stop, step) gives numbers from start up to but not including stop. while repeats as long as a condition is true. break exits a loop at once; continue skips to the next turn. A loop inside another is a nested loop and is used for patterns; loops with an accumulator are used for series sums.
Control Statements in Python: if-else, while and for – Normally Python runs lines one after another (sequence). Control statements change this flow. if-else chooses one of two paths; if-elif-else picks the first true condition from many. while repeats a block while a condition is true; for repeats once for each item of a sequence such as range(start, stop, step).
Lists in Python – A list is an ordered, mutable sequence of values of any type, written in square brackets: [4, 'a', 2.5]. Items are reached by index (0 from the left, −1 from the right) and can be changed in place. Operations: + (join), * (repeat), in / not in (membership) and slicing. Traversal uses for or while loops. Built-in functions and methods: len(), list(), append(), extend(), insert(), count(), index(), remove(), pop(), reverse(), sort(), sorted(), min(), max(), sum(). A nested list holds lists inside it, like a table (M[row][col]). Standard programs find the maximum, minimum and mean, do a linear search and count the frequency of elements.
Lists in Python: Create, Traverse, Change and List Methods – A list is an ordered, changeable collection written in square brackets, like [10, 20, 30]. Items are reached by index (from 0, or negative from the end) and slices. We traverse a list with a for loop, change items in place because lists are mutable, and use functions (len, max, min, sum, sorted, list) and methods (append, insert, extend, remove, pop, sort, reverse, count, index, clear) to work with it.
Dictionaries in Python – A dictionary is a mutable collection of key: value pairs written in curly brackets: D = {'Riya': 91, 'Aman': 85}. Values are reached by key (D['Riya']), not by position; a missing key raises KeyError. Keys must be unique and immutable (numbers, strings, tuples); values can be anything. D[key] = value adds a new pair or changes an existing value. Traversal uses for key in D. Useful functions and methods: len(), dict(), keys(), values(), items(), get(), update(), del, clear(), fromkeys(), copy(), pop(), popitem(), setdefault(), max(), min(), count via loops, and sorted(). A classic program counts how many times each character appears in a string.
Dictionaries in Python: Key-Value Pairs and Methods – A dictionary is a mutable collection of key: value pairs in curly braces, like {"Ravi": 85}. Keys are unique and immutable; values can be anything. We add or change a pair with d[key] = value, read with d[key] or d.get(key), traverse with for k in d, and use methods such as keys(), values(), items(), update(), pop(), popitem() and clear().
Introduction to NumPy: Creating Arrays from Lists – NumPy (Numerical Python) is a library for fast maths on arrays. An array is a grid of items that all have the same type. We make one from a list with np.array(list); a list of lists gives a 2-D array. Attributes ndim, shape, size and dtype describe it. Unlike lists, arrays do maths on every item at once.

3. Database Concepts and SQL

Database concepts · SQL with MySQL

Database Concepts: DBMS, Relations and Keys – Keeping data in separate files causes duplication, inconsistency and poor security. A database stores related data in one organised place, and a DBMS (like MySQL) is the software that manages it. In the relational model, data is kept in tables (relations) made of columns (attributes) and rows (tuples); a domain is the set of allowed values of a column. A candidate key uniquely identifies each row; one is chosen as the primary key and the others are alternate keys.
SQL with MySQL: Create Tables, Change Rows and Ask Questions – SQL (Structured Query Language) is the language used to talk to a relational DBMS like MySQL. DDL commands (CREATE, ALTER, DROP) define tables; DML commands (INSERT, UPDATE, DELETE) change rows; DQL (SELECT) reads data. Each column has a data type such as INT, FLOAT, CHAR, VARCHAR or DATE. SELECT … WHERE filters rows using relational operators, BETWEEN, AND/OR/NOT and IS NULL.

4. Introduction to Emerging Trends

Emerging technologies

Emerging Trends: AI, IoT, Cloud and Blockchain – Emerging technologies are new tools that are changing how we live and work. AI lets machines do smart tasks; machine learning lets them learn from data; NLP lets them use human language. AR adds virtual things to the real world, VR replaces it. Robots sense, think and act. IoT devices with sensors create big data, which smart cities use. Cloud computing rents out IaaS, PaaS or SaaS over the internet; grid computing joins many computers for one big job. Blockchain keeps a shared record that is very hard to change secretly.