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• Every file has associated with it a unique filename which is used to identify it on the disk.
• The filename consists of two parts, an extension (usually three letters) that identifies the type of data stored in the file, and a name part that can be up to eight characters long.
• The extension is separated from the name by a period
• The period serves as a delimiter, indicating where one portion of the filename ends, and the next begins.
• An extension is usually used to identify files that are related in some way.
• MS-DOS allows the following characters to be used in a filename and extension:

  • Uppercase and lowercase case letters A through Z
  • Numbers 0 through 9
  • Special characters $ # & @ ( ) ! ^ ` ~ { }
• An instruction given to a computer to perform a specific task is known as a command.
• A file can contain only data, or it can contain a set of instructions, called a program.
• The name part consists of up to eight alphabetic characters, while the extension part contains three characters.
• Client/Server (C/S) Computing: A network architecture where each computer or process on the network is either a client or a server.
• Client/Server Architecture: Provides an open and flexible environment for managing resources.
• Components of Client/Server Architecture: Clients: Devices or applications making requests.
• Servers: Computers or processes managing network resources.
• Communication Networks: Infrastructure connecting clients and servers.
• Server: Applications that run on computers and rely on servers for files, devices, and processing power.
• Middleware: Software connecting separate applications.
• Logical Tiers in Client/Server Architecture: Data Management: Handled by the server.
• Application Logic: Processed on both the server and the client.
• Presentation: Formatting data on the client.
• Client Types: Fat Client: Performs a significant amount of application processing.
• Thin Client: Relies heavily on the server for processing.
• Types of Servers: Database Server: Manages data.
• Application Servers, Audio/Video Servers, Web Servers, etc.: Provide specific functionalities.
• Communication Networks in Client/Server Computing: Definition: Networks connecting clients and servers.
• Function: Software application functions are separated into three distinct parts.
• Server Scalability: The capability of servers to scale either horizontally (more clients) or vertically (more servers).
• Importance: Allows for flexibility and increased computing resources.
• Client/Server Models: Two-Tier Servers: Application logic buried within the client or server.
• Three-Tier Servers: Middle-tier separates application logic from the user and data interface.
• Three-Tier Architecture: Describes the division of application processes between client and server.
• A Brief History: Open Platform: Evolution from mainframes to an open platform with mix-and-match capabilities.
• Fat Servers: Describes the distribution of application complexity between clients and servers.
• Middleware: Acts as the glue between clients and servers, facilitating communication.
• Systems with C/S Architecture: File Servers: Focus on file sharing and processing.
• Database Servers: Handle database queries and transactions.