The script integrates individual commands into a

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Unformatted text preview: tes the source program in extended language to a standard language source program by using the preprocessor, and the second pass translates the standard language source program to executable object code by using the standard language compiler. But in most cases of preprocessing, the user is given the feel of one-pass translation through creation of a library of system commands that, when invoked, runs through the multiple operations in response to a short sequence of keystrokes or one click of a picking device. Scripting Languages Command statements are used to instruct a computer to do some job. For example, a "run" or "exec" statement may be used to execute a program and a "copy" statement may be used to copy a file from one storage device 1 another. Often a user needs to execute a set of commands to perform a particular task. For example, to perform task, the user may be required to execute two independent programs, and after execution of the first program he/she may be required to copy the output file of the first program on to a device from which the second program expects the input. So in this case, the user needs to specify two execute commands for executing the two programs and a copy command before the second execute command. A scripting language is a programming language that allows programmers to integrate several such commands into a single command so that the programmer need not type all the commands every time he/she needs to perform the intended task. A program written in a scripting language is commonly referred to as a script. Scripting languages support variables and simple control structures to allow programmers to write scripts, which can conditionally execute or repeat the execution of certain commands. With these features, scripting languages may be used to define complex commands execution patterns. Another common use of scripting languages is in specifying execution environment setup for applications that are quite complex, yet flexible enough* to be...
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This document was uploaded on 04/07/2014.

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