A point and draw device is normally used to rapidly

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Unformatted text preview: d to type words and symbols. For example in Unix, the user has to type "del report.txt" to delete the file named report.txt. If the User types a command incorrectly, the command interpreter will respond with a message indicating that it did not understand the command. When this happens, the user has to just retype the command correctly. There is no problem in typing simple commands as illustrated in the example above. However, users often need to give detail instructions to the computer about their jobs when they submit them for execution. For example, while submitting a job for execution, a user may need to supply the following information: 1. His/her identification for security and accounting purposes. 2. The software and hardware resource requirements of the job. 3. The I/O device requirements of the job. 4. The directories in which the data files to be used by the job are stored. 5. The action, which the system should take in exceptional conditions, such as when the input data is missing or incorrect, or when an I/O device malfunctions. To facilitate this, systems, which support command-line interface, also support some type of command language (CL) or job-control language (JCL). Users can write codes in the JCL to give instructions to the system. These coded statements tell the operating system such things as the name of the job, the user's name and account number, the I/O devices to use during processing, the compiler to use if language translation is needed, where to find the data files, and so on. The command interpreter is designed to interpret the codes written in JCL and invoke appropriate system actions. Graphical User Interface User interface plays an important role in ease of use. The more intuitive the user interface of a system is, the easier it is to use. An intuitive user interface allows a user to use the system effectively even if he/she has never seen it before. That is, how the user interface works is very obvious to any user. Such an user interface is called user friendly....
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