Input-statements provide for user interaction with a running program by allowing variables to be assigned values that are supplied by a user. The input-statement enables the entry of mixed string and numeric data, with data items being separated by commas. The general syntactic form of the input-statement is
INPUT variable, ..., variable 1. input-statement = INPUT variable-list
2. variable-list = variable (comma variable)*
3. input-prompt = (implementation-defined) "? "
4. input-reply = input-list end-of-line
5. input-list = padded-datum (comma padded-datum)*
6. padded-datum = space* datum space*
7. datum = quoted-string / unquoted-string INPUT X 3.14159 INPUT X, A$, Y(2) 2,SMITH,-3 INPUT A, B, C 25,0 ,-15An input-statement causes the variables in the variable-list to be assigned, in order, values from the input-reply. In the interactive mode, the user of the program is informed of the need to supply data by the output of an input-prompt. In batch mode, the input-reply is requested from the external source by an implementation-defined means. Execution of the program is suspended until a valid input-reply has been supplied. The type of each datum in the input-reply shall correspond to the type of the variable to which it is to be assigned; i.e. , nume ri c-cons tan ts shall be supplied as input for numeric- variables, and either quoted-strings or unquoted-strings shall be supplied as input for string-variables. If the response to input for a string-variable is an unquoted-string, leading and trailing spaces shall be ignored (see 4). If the evaluation of a numeric datum causes an underflow, then its value shall be replaced by zero. Subscript expressions in the variable-list are evaluated after values have been assigned to the variables preceding them (i.e. to the left of them) in the variable-list. No assignment of values in the input-reply shall take place until the input-reply has been validated with respect to the type of each datum, the number of input items, and the allowable range for each datum.
The type of datum does not match the type of the variable to which it is to be assigned (nonfatal, the recommended recovery procedure is to request that the input-reply be re-supplied). There is insufficient data in the input-list (nonfatal, the recommended recovery procedure is to request that the input- reply be resupplied). There is too much data in the input-list (nonfatal, the recommended recovery procedure is to request that the input- reply be resupplied). The evaluation of a numeric datum causes an overflow (non- fatal, the recommended recovery procedure is to request that the input-reply be resupplied). A string datum contains too many characters (nonfatal, the recommended recovery procedure is to request that the input- reply he resupplied).
This Standard does not require an implementation to perform any editing of the input-reply, though such editing may be performed by the operating environment. It is recommended that the input-prompt consists of a question- mark followed by a single space. This Standard does not require an implementation to output the input-reply. It is recommended that implementations report an underflow as an exception and allow the input-reply to be resupplied.