Internal Format

Internal format is the data format resulting when data is internally converted using one of the conversion or processing codes provided with D3. As a general rule, internal format refers to the manner in which data is stored inside the system.

The main advantage of an internal format is that it takes much less time to compare two values.

For example, time values are not stored in external form. Rather, they are converted using the mt input processing code, which takes a legal external time, such as 14:00 (2:00 PM), and calculates the number of seconds past midnight for this value, which would be the internal value. In this case, the internal form would be 50400. The same mt code used as an output processing code can be used to convert the internal value to its external form.

Dates are easily manipulated if stored in an internal format. An input processing code of d takes an external date, uses a calculation to determine the number of days that have elapsed since December 31, 1967 (day 0 on the D3 calendar), and stores an internal julian date. A similar output processing code converts an internal date to its external form.

In addition, numerical values are easily handled by the system if they are all stored as integer amounts, and the decimal point (if any) is inserted only upon output. A typical American dollar amount (for example, $100.00) is converted upon input to an internal form of 10000 using the mr2 input processing code. A similar output processing code redisplays the figure as 100.00.

Another reason for using an internal format is to save storage space. For example converting the external form of SMALL, MEDIUM, and LARGE into S, M, and L. The internal values are reconstituted upon output.