ABSTRACT
The computer program needs inputs to process data. Programs have instructions that process the data as well as instructions to pull the data needed for processing. This chapter looks at all the instructions available for receiving inputs into the computer. The chapter begins with the ways of receiving inputs, enumerating the steps that include the process of receiving the inputs. Inputs are sent to the computers from the various input devices using the mechanisms of the interrupts, buffers, and the direct memory access (DMA). Then the file operations are described to receive data inputs from flat files, including the steps for opening the files for input, reading from them, and how the computer transfers the data from the flat files into the computer for processing. Although the usage of flat files has drastically come down in recent times, they still play an important role in data inputs, especially in the case of configuration information. Then we discuss receiving inputs from the database tables and their associated operations, such as connecting to the database, opening the table, and reading the records. The important aspects of forming the connection string are also discussed. As a significant amount of input comes from the keyboard via the input screens, the important aspects of the graphical user interface (GUI) and its screen controls are described in significant detail. Significant events like click, double-click, got-focus, lost-focus, form-load, and so on associated with the data controls are described. Then the common input statements used to receive inputs into the computer, for both flat files and database tables, are discussed in detail. The garbage in—garbage out (GIGO) phenomenon is well documented, and the chapter discussed this phenomenon and the ways and means to prevent it. Data validation during input, especially from the keyboard, is discussed in great detail to ensure that only the precise data is input for storage as well as for processing. A few significant techniques for data validation are discussed here while emphasizing the need for it. Finally, receiving inputs from machines like the automobiles, rockets, and other machines is briefly discussed.
