n. (context computing English) program that processes its input data to produce output that is used as input to another program
In computer science, a preprocessor is a program that processes its input data to produce output that is used as input to another program. The output is said to be a preprocessed form of the input data, which is often used by some subsequent programs like compilers. The amount and kind of processing done depends on the nature of the preprocessor; some preprocessors are only capable of performing relatively simple textual substitutions and macro expansions, while others have the power of full-fledged programming languages.
A common example from computer programming is the processing performed on source code before the next step of compilation. In some computer languages (e.g., C and PL/I) there is a phase of translation known as preprocessing.
Steps that are followed in Pre-Processing
1> The geometry (physical bounds) of the problem is defined
2> The volume occupied by the fluid is divided into discrete cells (meshing)
3> The physical modeling is defined - Eg. equations of motion + enthalpy + radiation + species conservation
4> Boundary conditions are defined. This involves specifying the fluid behavior and properties at the boundaries of the problem. For transient problems, the initial conditions are also defined.
5> The simulation is started and the equations are solved iteratively as a steady state or transient
6> Finally a post-processor is used for the analysis and visualization of the resting solution
Usage examples of "preprocessor".
The numbers on the sheet told him that the surveillance programs running in the preprocessor that interfaced the system to the outside world via the Infonet lines had trapped and aborted no fewer than fifty-seven illegal attempts to gain access to the Sudbury database from anonymous places elsewhere.