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Integer 2s Complement Arithmetic

In 2s complement arithmetic, negative numbers are represented as the value that, when added to a positive number of the same magnitude, equals zero. A negative value is formed by complementing each binary bit of the positive number, and then adding 1. For negative values, the most significant bit (MSB) is always 1. This arithmetic is commonly used by computers when dealing with integers.

In decimal, the minus sign character is used to indicate negative values, but in all other bases it is not shown.

Here is an example in the 32 bit integer mode for hexadecimal radix:

1
[-]
2
[ENTER]
Displays: FFFF FFFF

Converting this value to decimal will show -1.

Hint: In the Numeric Screen page of the Options Window, you will find an option to show negative values in red. This setting will highlight negative 2s complement values.

Floating Point Mode

In floating point base-N mode, 2s complement arithmetic is not used and the sign is held independently. Thus, there are 64 bits of precision plus one extra sign flag. In this mode, the decimal value -1 will be shown as -0x1 when converted to hexadecimal.

The permissible numerical range in floating point base-n mode is +/-18446744073709551615. In the decimal radix, therefore, a maximum of 20 digits is allowed where necessary, but often DreamCalc will present results using only 18 decimal digits. This behavior is normal and ensures accuracy of +/-1 of the last digit. Similarly, rounding is done in other radix as applicable.

Setting the Radix

In all base-N modes, you may set the radix to any value between 2 and 16. You'll find you can set commonly used bases, such as decimal, hexadecimal, octal and binary, from the keypad at the touch of a button. Changing the radix does not reset the display—the display value is simply converted. For bases higher than 10, use the keys marked A - F as digits. Additional radix settings can be found under the Modes->Base-N->Other Radix menu, or may be set using the [MODE] key.

Digit Grouping & Padding

You may set digit grouping every four characters for bases which align to byte boundaries, as follows:

• Binary - nibble grouping
• Quadrary - byte grouping
• Hexadecimal - word grouping

For all other bases, digits are not grouped, except decimal which will group in thousands as in Normal Math mode. Digit grouping is enabled by default.

You can also enable or disable zero padding of lead digits. When enabled, lead zeros will be displayed so as to indicate the position of every available digit. Leading zeros are not shown in the decimal radix. This setting is disabled by default.

Both these settings are available from the Numeric Screen page of the Options Window or by using [MODE] key in base-n mode.