12th Computer Science Important 1 Mark Questions Chapter Wise

By Ravi Kumar · 15 Sep 2026 · 4 min read

The one-mark section of Class 12 Computer Science is built from precise definitions and small Python facts. If you know the exact term the textbook uses for each idea, most questions take seconds. Here is what each chapter's book back questions test.

Unit 1: Function

Small sections of code that perform a particular task are subroutines
Variables in a function definition are parameters; values passed in are arguments
An interface defines what an object can do; the implementation carries it out
Pure functions give the same result for the same arguments; impure functions cause side effects

Unit 2: Data Abstraction

Constructors build an abstract data type; selectors retrieve information from it
A data type whose representation is known is concrete; one whose representation is unknown is abstract
Bundling two values together gives a pair; classes let you name the parts of a multi-item object

Unit 3: Scoping

Scope is the visibility of variables in different parts of a program
Binding a name to an object is mapping, done with =; namespaces are the containers for these mappings
Local scope refers to variables defined in the current function
Private members are accessible only within the class; protected members also in subclasses; public members from outside

Unit 4: Algorithmic Strategies

The word algorithm comes from the mathematician al-Khowarizmi
Efficiency is measured by time and space; selection sort needs the minimum number of swaps
Big O is the worst case, Big Ω is its reverse, and Θ represents the average case
Binary search is also called half-interval search
Storing previously calculated values in dynamic programming is memoization

Unit 5: Python Variables and Operators

Python was developed by Guido van Rossum; >>> is the interpreter prompt
Ctrl + N creates a new program; # starts a comment; a comma prints several items on one line
Relational operators are also called comparative operators; the ternary operator is the conditional operator

Unit 6: Control Structures

Python has three important control structures: sequential, alternative (branching) and iterative
elif is short for else if; indentation defines blocks
pass is used as a placeholder; for is a definite loop
An if or else line must end with a colon

Unit 7: Python Functions

A function that calls itself is recursion; an anonymous function is a lambda
def begins a function block and return exits it
Required arguments are passed in the correct positional order
Data types need not be declared, but keywords cannot be used as function names

Unit 8: Strings and String Manipulation

Strings are immutable; + concatenates; triple quotes create multiline strings
[ ] is the slicing operator, and the stride is the third argument of a slice
%E prints exponential notation in upper case; { } are placeholders for format()
A subscript can be positive or negative

Unit 9: Lists, Tuples, Sets and Dictionary

len() counts elements; append() adds one element and extend() adds several
type() tells you the data type of an object
Symmetric difference contains elements in either set but not in both
In a dictionary, a colon separates each key from its value

Unit 10: Python Classes and Objects

Functions defined inside a class are methods; members are accessed with the dot operator
__init__() runs automatically when an object is created; __del__() is the destructor
A private variable is prefixed with __; creating an object is instantiation

Unit 11: Database Concepts

A table is a relation and a tuple is a row
The hierarchical model represents parent-child, one-to-many relationships
E F Codd proposed the relational model and is called the father of relational databases; Chen developed the ER model
σ (sigma) is the symbol for SELECT in relational algebra

Unit 12: Structured Query Language (SQL)

DDL commands define and modify table structures
ALTER changes a table's structure; DROP deletes a table with its structure
SELECT generates queries; ORDER BY sorts the result

Unit 13: Python and CSV Files

A CSV file is a flat file; CRLF means Carriage Return and Line Feed
Python's csv module handles CSV files; binary mode is for non-text files
next() skips a row; DictReader() maps rows to dictionaries

Unit 14: Importing C++ Programs in Python

HTML is not a scripting language
Importing a C++ program into Python is called wrapping; Boost is a framework for it
API stands for Application Programming Interface; the OS module interfaces with Windows

Unit 15: Data Manipulation through SQL

SQLite is a relational database system; a cursor traverses and fetches records
Changes are saved with commit; execute() runs an SQL command
AVG() and MAX() are aggregate functions; DISTINCT removes duplicates
sqlite_master is the master table

Unit 16: Data Visualization using Pyplot

matplotlib.pyplot is the package for 2D charts; PIP installs packages
A dashboard combines resources into a single visual display
A line chart shows a trend over time; plt.pie() draws a pie chart and autopct shows percentages

How to revise this section

Test yourself rather than re-reading. Turn each bullet into a question, answer it from memory, and keep a single page of the ones you miss. The full solved sets are on the Class 12 Computer Science section, where every chapter also has a timed practice test.