12th Computer Applications One Mark Questions and Book Back Answers

About Computer Applications

Medium ~20 h study

Most of what you do on a computer today, from reading a school website to paying a bill with UPI, rests on the topics in this book. Class 12 Computer Applications teaches you how those things are built: how a page layout is designed, how data sits in tables, how a PHP script reads a form and talks to a database, how computers are wired into a network, and how money moves safely during an online purchase.

The chapters follow a sensible order. You begin with multimedia and desktop publishing in Adobe PageMaker, which is mostly visual work. Next comes the database chapter, where you learn how tables, rows, columns and keys store data. Then you write PHP: variables, operators, conditions, loops, functions, arrays, forms and files, and finally a script that connects to MySQL. After that the book turns to networks, the Domain Name System and cabling, and closes with e-commerce, payment systems, security and EDI.

Exam questions test both definitions and application. You may be asked to explain a protocol, write a small PHP program, give the colour order of a T568B cable or compare symmetric and asymmetric encryption. Learning the words by heart is not enough. You should be able to say what happens when a script runs on the server, how a packet finds its destination and why a form uses POST instead of GET.

What you'll learn

• Design a simple publication such as a brochure or notice using Adobe PageMaker.
• Draw an ER diagram and turn it into related tables with primary and foreign keys.
• Write SQL queries to insert, update, filter and retrieve records.
• Write PHP programs that use variables, conditions, loops, functions and arrays.
• Collect HTML form data in PHP and validate it on both the client and the server.
• Connect a PHP page to a MySQL database and display records from a table.
• Make a straight-through Ethernet cable with an RJ45 connector using the T568B colour order.
• Compare symmetric and asymmetric encryption and explain how they protect online payments.

Before you start

• Basic knowledge of computer hardware, operating systems and managing files and folders
• Familiarity with common HTML tags and the structure of a web page
• Simple logical thinking, such as following the steps of an algorithm or flowchart

Computer Applications — the syllabus in depth

What the Computer Applications Book Covers

Multimedia and Desktop Publishing

The first unit explains the parts of multimedia: text, hypertext, images (raster and vector), sound and video, along with their common file formats. The practical side is page layout in Adobe PageMaker. You learn to work with text blocks, split and join them, place text from a word processor, and set up master pages so that logos, page numbers and guides repeat on every page of a publication.

Relational Database Management Systems

Here you see how data is stored in tables made of rows (records) and columns (attributes), and how primary and foreign keys link one table to another. The chapter introduces data models and the ER (entity-relationship) diagram, and then SQL commands for defining data, changing data and controlling access. You practise creating tables and writing queries that insert, update, select, group and filter records.

Server-Side Scripting with PHP

This is the programming part of the book. You start with PHP syntax, comments and variable naming, then write if, else if and switch statements and for, while, do-while and foreach loops. Later chapters add user-defined functions and indexed, associative and multidimensional arrays. The Forms and Files chapter shows how a PHP script collects values from HTML form controls, validates them on the client and the server, and opens, reads, writes and uploads files.

Connecting PHP and MySQL

A web page becomes truly dynamic when it reads from a database. In this chapter you use the MySQLi functions to open a connection, run select, insert and update queries from PHP, and close the connection. The result is a page that shows the latest records every time it loads.

Computer Networks and Cabling

The networking chapters describe what a network is, how the Internet grew, and how intranets and extranets differ. You study the OSI and TCP/IP reference models, the Domain Name System and the structure of a URL. The cabling chapter compares twisted pair, coaxial and fibre optic cables, explains how to crimp an RJ45 connector using the T568A and T568B colour codes, and the open source chapter introduces network simulation and monitoring tools.

E-Commerce and Security

The last chapters cover business models used in e-commerce, ways of earning revenue online and electronic payment systems such as credit cards, debit cards, e-wallets and UPI. The security chapter explains symmetric and asymmetric encryption, digital certificates, digital signatures and authentication. The final chapter describes EDI, the paperless exchange of standard business documents between trading partners.

How to study Computer Applications

Treat this subject as half theory and half practice. Read a chapter, then sit at a computer and try what it describes. Start with the PageMaker and database chapters, since they introduce layout and structured data. Give the PHP chapters more time than the rest, and actually type and run every program so you see how conditions, loops and arrays behave.

A simple routine that works for most students:

1. Write and run one or two short PHP scripts every day, and fix the errors yourself.
2. Write SQL commands on paper, because exam questions expect the exact syntax.
3. Redraw the OSI and TCP/IP layer diagrams and practise the steps for making an Ethernet cable.
4. Work through previous public exam question papers to get used to the question pattern and your timing.

Keep revising short terms from databases, networking protocols and e-commerce, since many one-mark questions come from these. Test your PHP programs on a local server such as WAMP or XAMPP. Seeing the output in the browser is the quickest way to understand what your code does.

Common mistakes to avoid

• Leaving out the semicolon at the end of a PHP statement. PHP stops with a parse error, so end every statement with a semicolon.
• Writing a PHP variable without the dollar sign. Every variable name must begin with $, for example $total, not total.
• Using + to join strings in PHP. The + operator is for arithmetic; strings are joined with the dot operator, as in $first . $last.
• Mixing up the wire order while crimping. Follow the T568A or T568B colour sequence exactly, pin by pin, at each end.
• Assuming POST is encrypted. POST only keeps the data out of the URL; use it for passwords and large data, and use GET for short, visible query strings.

Frequently asked questions

What is the difference between static and dynamic web pages?

A static web page shows the same content to every visitor until the developer edits the file. A dynamic web page builds its content when it is requested, usually by running a server-side script such as PHP that reads from a database, so the page can change from one visit to the next.

What are the main parts of a computer network?

A network is made of nodes, such as computers, mobile phones, printers and servers, joined by a transmission medium. The medium can be wired, like twisted pair or fibre optic cable, or wireless, like Wi-Fi. Protocols such as TCP/IP set the rules for how the nodes send and receive data.

How do I connect to a MySQL database using PHP?

Use mysqli_connect() with four arguments: the server name, the username, the password and the database name. Check the result straight away with mysqli_connect_error() and stop with an error message if the connection failed. Only then run queries with mysqli_query(), and close the connection with mysqli_close() at the end.

What is a master page in Adobe PageMaker?

A master page holds items that must appear on many pages, such as a logo, page numbers, headers and guides. Whatever you place on the master page appears on every page based on it, and a change made there shows up on all those pages at once, which saves you from editing each page by hand.

What are primary keys and foreign keys?

A primary key is a column, or set of columns, whose value is unique for every record in a table, such as a register number. A foreign key is a column in another table that holds values of that primary key. It links the two tables and makes sure a record cannot refer to something that does not exist.

What is the difference between symmetric and asymmetric encryption?

Symmetric encryption uses one secret key to both encrypt and decrypt. It is fast, but the key must be shared safely. Asymmetric encryption uses a pair of keys: data locked with the receiver's public key can only be opened with the receiver's private key, which is never shared.

What does the Domain Name System do?

DNS works like a telephone directory for the Internet. It translates a domain name such as www.tn.gov.in into the numerical IP address of the server, so the browser can reach the site without you having to remember a string of numbers.

What is electronic data interchange (EDI)?

EDI is the computer-to-computer exchange of business documents, such as purchase orders and invoices, in a standard format agreed by trading partners. Because no paper or retyping is involved, there are fewer data entry errors, and orders and shipments are processed faster and at lower cost.