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AEDIT$–ASCII Image Composition Editing Package
Scientific Format
The scientific format is similar to the fixed decimal format, but it has an exponent at the
right. The exponent consists of an optional exponent character (usually 'E' for singleprecision
and 'D' for double-precision numbers) followed by the exponent's sign (either
"+" or "-") and the exponent's digits. Exponents of single-precision numbers are always
edited as a 2-digit value, and those of double-precision numbers are always edited as a
3–digit value.
The x parameter specifies the total number of character positions to be occupied by the
edited number, including signs, digits, decimal point, and exponent character. If the
edited numbers require more character positions than are specified by the value of x, the
x parameter is ignored and the required character positions are used.
The y parameter specifies the total number of mantissa digits to appear in the edited
number. It includes the digits on both sides of the decimal point but not the decimal
point itself. The placement of the decimal point within the y digits of the mantissa is
determined by the value in the packet cell fps. This is the number of digits to appear to
the left of the decimal point. It is normally set to one.
The floating-point routines provide rounding up to 8 significant digits for single-precision
floating-point numbers and 17 significant digits for double-precision floating-point
numbers. This is because the 2200 single-precision and the double-precision formats
use 27 and 60 bits for the mantissa, respectively. These can represent up to 8 and 18
significant digits in these cases. As rounding is done at a maximum of the 18th digit, the
maximum value of y for which a rounded result will be produced is 8 for single-precision
and 17 for double-precision floating-point numbers. The value of x should allow for the
sign, decimal point, the exponent character, the exponent sign, and the exponent digits.
For example, the following numbers are in scientific format:
8.66E+01 Requires parameter values of x ≥ 8 and y = 3.
-1.3375E-10 Requires parameter values of x ≥ 11 and y = 5.
5.164D+003 Requires parameter values of x ≥ 10 and y = 4.
7833 1733–004 4–15