When using informats with the INPUT statement, what should you consider?

Using informats with the INPUT statement is crucial for accurately reading data from external files. Informats are designed to specify how data should be read into SAS, especially when the data format in the file does not match the default reading behavior of SAS.

Choosing the correct informat allows SAS to interpret the incoming data correctly based on its actual format—whether it is a date, time, or a specific character string representation. For example, if a date is formatted as "YYYY-MM-DD" in the file, using an appropriate date informat ensures that SAS recognizes and imports this data as a date value rather than as character data.

The other options do not accurately reflect the importance of informats: character informats are only one part of the picture; numeric values do not require specific lengths set by the user because SAS automatically handles numeric size based on the data inherent to the variable; and informats certainly do impact the data reading process by guiding how the data is interpreted during the input phase. Hence, understanding and applying informats correctly is key to ensuring data integrity in SAS.