A format specification cannot specify more output characters than the external record can contain. For example, a line printer record cannot contain more than 133 characters, including the carriage control character.
The field width specification w must be large enough to accommodate all characters that the data transfer can generate, including an algebraic sign, decimal point, and exponent. For example, the field width specification in an E field descriptor should be large enough to contain d+5 or d+e+3 characters for positive numbers, and d+6 or d+e+4 characters for negative numbers.
The first character of a record transmitted to a line printer or terminal is typically used for carriage control; it is not printed. The first character of such a record should be a space, 0, 1, $, +, or ASCII NUL. Any other character is treated as a space.