So the first two are easy. Informats are instructions for how to convert text into values. Formats are instructions for how to convert values into text.   In this program only the use of the NLNUM informat and format are necessary as SAS does not need special instructions for reading normal text or numbers and will default to displaying numbers using BEST12 format.   But the first INFORMAT statement also has a side effect of causing the compiler to define STRDATE as a character variable with a length of 30 bytes since this is the first place that it sees the variable referenced. ... View more