Definition:

A transaction is a sequence of steps that result in a change in the state of a system. It is a single unit of work that is performed in a specific order.

Key Characteristics of Transactions:

1. Atomicity: A transaction is either completed successfully or rolled back to its initial state if there is any error.2. Consistency: A transaction brings the system from one consistent state to another, ensuring that the system remains in a valid state after every transaction.3. Isolation: Transactions are isolated from each other, meaning that one transaction cannot see or affect the state of another transaction.4. Durability: Once a transaction is committed, its changes are permanent and will survive system failures.

Types of Transactions:

• Read-only transactions: Read data from the system without making any changes.
• Write-only transactions: Make changes to the system data, but do not read any data.
• Read-write transactions: Read and write data within a single transaction.

Examples:

• Banking transaction: Deposits, withdrawals, and transfers are all transactions.
• E-commerce purchase: Adding items to the cart, checkout, and payment are all transactions.
• Database update: Inserting, updating, and deleting data in a database are transactions.

Transactions in Different Systems:

• Operating systems: Transactions are used in operating systems to ensure consistency of data across multiple operations.
• Databases: Transactions are used to maintain the consistency of database data.
• Web applications: Transactions are used to ensure that changes made to a web application are either committed or rolled back in case of errors.

Conclusion:

Transactions are an essential concept in many systems to ensure data consistency and integrity. By defining a unit of work that is atomic, consistent, isolated, and durable, transactions provide a foundation for reliable and robust systems.