Computer Science 9608

Questions and Answers

What best describes the logical organization of data?

The abstract way that the computer program accesses data. (correct)

The actual physical structure of data in memory.

The sequence of bits that represent data in memory.

The specific location where records are stored.

Which of the following statements about a serial file is true?

Records in a serial file are stored in alphabetical order.

A serial file contains records with a defined format for input/output. (correct)

All records in a serial file are accessed randomly.

A serial file can have records with no defined format.

What is the primary key in a database context?

A field that is used for sorting data only.

A unique field or set of fields identifying a record. (correct)

A field that contains duplicated values.

A collection of related records.

What method can be used to locate a record in a database?

Records can be found by searching, jumping, or a combination of both. Signup and view all the answers

Which statement best captures the distinction between logical and physical organization of data?

Logical organization deals with how data is accessed abstractly, while physical organization specifies the actual storage structure. Signup and view all the answers

What is the primary method of accessing records in a sequential file?

Sequential access by reading each record in order Signup and view all the answers

What is a characteristic of indexed sequential files?

They use a direct index to link to sections of records. Signup and view all the answers

Which of the following best describes the reasoning behind sequential processing theory?

It evaluates correctness of retrieved records in a first-come basis. Signup and view all the answers

In what way were sequential files originally designed to operate?

On magnetic tapes optimized for sequential access Signup and view all the answers

What does the key field in an indexed sequential file do?

Provides direct access to a record's location in the index Signup and view all the answers

Study Notes

Logical vs. Physical Organization of Data

Logical Organization: Represents how programs access data abstractly, utilizing logical structures like linked lists.
Physical Organization: Refers to the actual arrangement of data in memory, detailing the sequence of bits.

Definitions

Database: A collection of related files.
File: A collection of related records, which can be text files or binary files (including formats like graphic and word-processing).
Record: Consists of related fields.
Key Field: Uniquely identifies each record; a primary key contains unique values within a table.

Basics (General Idea)

Records can be stored at various indices, requiring knowledge of their locations for retrieval.
Options for finding a record include searching, jumping directly to a location, or a combination of both.

Serial Files

Serial File: Contains records without a defined order; often used in transaction records (e.g., banking).
Records are entered in chronological order, and a defined format is necessary for correct data input/output.

Sequential Files

Records are stored sequentially based on a key field, such as names alphabetically.
Originally designed for magnetic tape operation, retrieval follows a sequential search where each name is checked in order.

Indexed Sequential Files

Similar to an index in a book, a file index organizes records for faster access.
Involves sequential searching for the key field, followed by locating the desired record in a specified section.

Direct Access Files

Records can be accessed randomly through a method called "hashing," which uses the key field's value to compute a position.
The hashing process may lead to non-unique positions (e.g., using formulas like Index ← CustomerID MOD 10).

Direct Access vs. Sequential File

Direct Access allows for random record retrieval, while Sequential Files require a linear search process based on order.

Description

Explore the distinctions between logical and physical data organization in this Computer Science quiz. Understand the abstract data structures and the actual memory layout that underpin computer programs. Test your knowledge on the essential concepts that drive data organization in computing.