The four character data category keyword is a predefined abbreviation or mnemonic indicating the type of data that is to be input, e.g. COOR - COORdinate positions, MATE - MATErial properties, etc. Every data category must contain at least a data category keyword. If a particular application of the program does not require the information pertaining to a certain data category, then the user must enter 'NONE' as the data category keyword to indicate this.