1’s complement A form of signed binary notation in which negative numbers are created by complementing all bits of a number, including the sign bit.
10’s complement A way of writing decimal numbers where a negative number is generated by adding 1 to its 9’s complement.
2’s complement A form of signed binary notation in which negative numbers are created by adding 1 to the 1’s complement form of the number.
8421 Code (or NBCD; natural binary coded decimal) A BCD code that represents each digit of a decimal number by its 4-bit true binary value.
9’s complement A way of writing decimal numbers where a number is made negative by subtracting each of its digits from 9 (e.g., 726 999 726 273 in 9’s complement).
Addend The number in an addition operation that is added to another.
Alphanumeric code A code used to represent letters of the alphabet and numerical characters.
ASCII American Standard Code for Information Interchange. A 7-bit code for representing alphanumeric and control characters.
Augend The number in an addition operation to which another number is added.
BCD Binary coded decimal. A code that represents each digit of a decimal number by a 4-bit binary value.
BCD adder A parallel adder whose output is in groups of 4 bits, each group representing a BCD digit.
Borrow A digit brought back from a more significant position when the subtrahend digit is larger than the minuend digit.
Carry A digit which is “carried over” to the next most significant position when the sum of two single digits is too large to be expressed as a single digit.
Carry bit A bit that holds the value of a carry (0 or 1) resulting from the sum of two binary numbers.
Cascade To connect an output of one device to a input of another, often for the purpose of expanding the number of bits available for a particular function.
Case shift Changing letters from capitals (UPPERCASE) to small letters (lowercase) or vice versa.
Component A complete VHDL design entity that can be used as a part of a higher-level file in a hierarchical design.
Component declaration statement A statement that defines the input and output port names of a component used in a VHDL design entity.
Component instantiation statement A statement that maps port names of a VHDL component to the port names, internal signals, or variables of a higher-level VHDL design entity.
Difference The result of a subtraction operation.
End-around carry An operation in 1’s complement subtraction where the carry bit resulting from a sum of two 1’s complement numbers is added to that sum.
Excess-3 code A BCD code that represents each digit of a decimal number by a binary number derived by adding 3 to its 4-bit true binary value. Excess-3 code has the advantage of being “self-complementing.”
Expander buffer A MAX PLUS II primitive that supplies an inverted product term for general use within a CPLD.
Fast carry (or look-ahead carry) A gate network which generates a carry bit directly from all incoming operand bits, independent of the operation of each full adder stage.
Full adder A circuit that will add a carry bit from another full or half adder and two operand bits to produce a sum bit and a carry bit.
GENERATE statement A VHDL construct that is used to create repetitive portions of hardware.
Gray code A binary code which progresses such that only one bit changes between two successive codes.
Half adder A circuit that will add two bits and produce a sum bit and a carry bit.
Hierarchy A group of design entities associated in a series of levels or layers in which complete designs form portions of another, more general design entity. The more general design is considered to be the higher level of the hierarchy.
Instantiate To use an instance of a component.
Magnitude bits The part of a signed binary number that tell us how large the number is (i.e., its magnitude).
Minuend The number in a subtraction operation from which another number is subtracted.
Operand A number upon which an arithmetic function operates (e.g., in the expression x y z, x and y are the operands).
Overflow An erroneous carry into the sign bit of a signed binary number which results from a sum larger than can be represented by the number of magnitude bits.
Parallel binary adder A circuit, consisting of n full adders, which will add two n-bit binary numbers. The output consists of n sum bits and a carry bit.
Port An input or output of a VHDL design entity or component.
Ripple carry A method of passing carry bits from one stage of a parallel adder to the next by connecting COUT of one full adder to CIN of the following stage.
Self-complementing A code that automatically generates a negative-equivalent (e.g., 9’s complement for a decimal code) when all its bits are inverted.
Sign bit A bit, usually the MSB, that indicates whether a signed binary number is positive or negative.
Signed binary arithmetic Arithmetic operations performed using signed binary numbers.
Signed binary number A binary number of fixed length whose sign is represented by one bit, usually the most significant bit, and whose magnitude is represented by the remaining bits.