Which one of the following is commonly used to define the overall design of the database?a.Application programb.Schemac.Data definition languaged.Source code

Step 1: Break Down the Problem

We need to identify which option is commonly used to define the overall design of a database.

Step 2: Relevant Concepts

In database terminology, the overall design is typically referred to as the "schema." The schema outlines the structure of the database, including how data is organized and how the relationships between data elements are defined.

Step 3: Analysis and Detail

Let’s analyze each of the provided options:

1. Application program: Refers to software applications that interact with the database but do not define its design.
2. Schema: Represents the logical configuration of all or part of a relational database. The schema defines tables, fields, relationships, and other database elements.
3. Data definition language (DDL): A subset of SQL used to define or alter database structures, but it describes the schema rather than being the actual schema itself.
4. Source code: Refers to the programming instructions written for applications and is not related to the structure of the database.

Step 4: Verify and Summarize

Based on the analysis above, the term that best matches the description of "defining the overall design of the database" is clearly the schema.

Final Answer

The correct choice is b. Schema.