CBSE Class 12 Computer Science — NCERT Solutions

A syntax error is detected when the rules of the programming language are not followed while writing the program. Such errors are also called parsing errors. The text says that syntax errors are also handled as exceptions, so every syntax error is an exception.

But many exceptions occur after the program has started executing, even when the program is syntactically correct. Examples are ZeroDivisionError when dividing by zero, NameError when a variable is not defined, and IOError when a file cannot be opened. These are exceptions, but not syntax errors. So, every exception cannot be a syntax error.

• ImportError is raised when the requested module definition is not found. Example: trying to import a module that does not exist.
• IOError is raised when the file specified in a program statement cannot be opened. Example: trying to open a file with a wrong name or from a wrong location.
• NameError is raised when a local or global variable name is not defined. Example: using a variable before assigning any value to it.
• ZeroDivisionError is raised when the denominator in a division operation is zero. Example: 10/0.

Text file vs binary file:

• A text file consists of readable characters such as alphabets, numbers, and symbols. Its contents are stored as ASCII/Unicode byte values and can be opened in a text editor.
• A binary file stores data as bytes that do not represent readable characters. It may contain images, audio, video, executable files, etc., and needs specific software to read or write it.

• readline() reads one complete line from a file. If a number is given, it reads up to that many bytes, but not beyond the newline character.
• readlines() reads all lines from a file and returns them as a list of strings.

A stack is a linear data structure because its elements are arranged in a sequence.

A stack follows the LIFO rule, so the statement is incorrect.

A queue is a linear list of elements in which insertion and deletion take place from different ends.

Use Bubble Sort on the list
$[7, 11, 3, 10, 17, 23, 1, 4, 21, 5]$.

• Pass 1: largest element moves to the end.

Result: $[7, 3, 10, 11, 17, 1, 4, 21, 5, 23]$

• Pass 2: next largest moves to its position.

Result: $[3, 7, 10, 11, 1, 4, 17, 5, 21, 23]$

• Pass 3: next largest moves to its position.

Result: $[3, 7, 10, 1, 4, 11, 5, 17, 21, 23]$

So after three complete passes, the partially sorted list is:
$[3, 7, 10, 1, 4, 11, 5, 17, 21, 23]$.

Use linear search, so compare the key with elements from left to right.

List: $[1,-2,32,8,17,19,42,13,0,44]$

For key = 8

Position found = 4

For key = 1

Position found = 1

For key = 99

Search is unsuccessful.

For key = 44

Position found = 10

Required data to be maintained are:

• Declare exam results and print e-certificates: student name, roll number, marks/grades, result status, certificate details.
• Register participants in an exhibition and issue biometric ID cards: participant name, contact details, exhibition registration details, and biometric data such as fingerprint/iris data.
• Search for an image by a search engine: image-related data/metadata such as image type, size, resolution, tags, and other identifying information.
• Book an OPD appointment with a hospital in a specific department: patient name, contact details, hospital/department name, date, time, and appointment number.

So, different services require different kinds of structured data to be stored and maintained.

a) Database — a collection of logically related records.

b) Meta-data — the file/description of the data stored in the database.

c) Primary key — the attribute that can uniquely identify tuples in a relation.

d) NULL — the special value used when actual data is unknown.

e) Alternate key — an attribute that can uniquely identify tuples but is not chosen as the primary key.

f) DBMS — software used to create, manipulate, and maintain a relational database.

RDBMS (Relational Database Management System):

An RDBMS is a type of Database Management System (DBMS) that stores data in the form of related tables (relations). Each table consists of rows (records/tuples) and columns (attributes/fields). The relationships between tables are established using keys (Primary Key and Foreign Key).

Two popular RDBMS software:

1. MySQL
2. Oracle

• ARPANET — Advanced Research Projects Agency Network
• MAC — Media Access Control
• ISP — Internet Service Provider
• URI — Uniform Resource Identifier

Data communication refers to the exchange of data between two or more networked or connected devices. The data may be text, image, audio, video, or multimedia.

The main components of data communication are:

1. Sender — the device that sends data.
2. Receiver — the device that receives data.
3. Message — the data or information being exchanged.
4. Communication medium — the path or link through which the message travels.
5. Protocols — the rules that must be followed for successful communication.

A computer is considered safe when it is not connected to a network or the Internet because it is then isolated from outside connections. Without a link to external devices or computers, it is not exposed to security threats coming from the network, so illegitimate access or misuse becomes much harder.