http://support.sas.com/kb/24/590.html
new_variable=input(original_variable,informat)中的informat是指new_variable的输入格式（数值型格式）;
new_variable=put(original_variable,format)中的format是指original_variable的输出格式（数值型格式）.

***input();
Convert character to numeric

To convert character values to numeric values, use the INPUT function.

new_variable = input(original_variable, informat.);

The informat tells SAS how to interpret the data in the original character variable.

For example, if you have a simple string of digits like 12345678, you can use the basic numeric informat w.d:

data new;
   char_var = '12345678';
   numeric_var = input(char_var, 8.);
run;

***put();
To convert numeric values to character, use the PUT function:

new_variable = put(original_variable, format.);

The format tells SAS what format to apply to the value in the original variable. The format must be of the same type as the original variable. For example, if you are using the PUT function to convert a numeric value to character, the format must be a numeric format.

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