Q1. What is Client-server Computing?
Ans: The short answer: Client/server is a computational architecture that involves client processes requesting service from server processes. The long answer: Client/server computing is the logical extension of modular programming. Modular programming has as its fundamental assumption that separation of a large piece of software into its constituent parts ("modules") creates the possibility for easier development and better maintainability. Client/server computing takes this a step farther by recognizing that those modules need not all be executed within the same memory space. With this architecture, the calling module becomes the "client" (that which requests a service), and the called module becomes the "server" (that which provides the service). The logical extension of this is to have clients and servers running on the appropriate hardware and software platforms for their functions. For example, database management system servers running on platforms specially designed and configured to perform queries, or file servers running on platforms with special elements for managing files. It is this latter perspective that has created the widely-believed myth that client/server has something to do with PCs or Unix machines.
Q2 What is a Client process?
Ans: The client is a process (program) that sends a message to a server process (program), requesting that the server perform a task (service). Client programs usually manage the user- interface portion of the application, validate data entered by the user, dispatch requests to server programs, and sometimes execute business logic. The client-basedprocess is the front- end of the application that the user sees and interacts with. The client process contains solution-specific logic and provides the interface between the user and the rest of the application system. The client process also manages the local resources that the user interacts with such as the monitor, keyboard, workstation CPU and peripherals. One of the key elements of a client workstation is the graphical user interface (GUI). Normally a part of operating system i.e. the window manager detects user actions, manages the windows on the display and displays the data in the windows.
Q3 What is a Server process?
Ans : A server process (program) fulfills the client request by performing the task requested. Server programs generally receive requests from client programs, execute database retrieval and updates, manage data integrity and dispatch responses to client requests. Sometimes server programs execute common or complex business logic. The server-based process "may" run on another machine on the network. This server could be the host operating system or network file server; the server is then provided both file system services and application services. Or in some cases, another desktop machine provides the application services. The server process acts as a software engine that manages shared resources such as databases, printers, communication links, or high powered-processors. The server process performs the back-end tasks that are common to similar applications.
Q4 What is a Two-Tier Architecture?
Ans : A two-tier architecture is where a client talks directly to a server, with no intervening
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server. It is typically used in small environments (less than 50 users). A common error in client/server development is to prototype an application in a small, two-tier environment, and then scale up by simply adding more users to the server. This approach will usually result in an ineffective system, as the server becomes overwhelmed. To properly scale to hundreds or thousands of users, it is usually necessary to move to a three-tier architecture.
Q5 What is a Three-Tier Architecture?
A three-tier architecture introduces a server (or an "agent") between the client and the server. The role of the agent is manyfold. It can provide translation services (as in adapting a legacy application on a mainframe to a client/server environment), metering services (as in acting as a transaction monitor to limit the number of simultaneous requests to a given server), or intellegent agent services (as in mapping a request to a number of different servers, collating the results, and returning a single response to the client.
