Sign bit
Encyclopedia
In computer science
, the sign bit is a bit
in a computer numbering format that indicates the sign
of a number. In IEEE format, the sign bit is the leftmost bit (most significant bit
). Typically if the sign bit is 1 the number is negative (in the case of two's complement
integer
s) or non-positive (for ones' complement integer
s, sign-magnitude integer
s, and floating point
numbers), while 0 indicates a positive number.
When an 8-bit value is added to a 16-bit value using signed arithmetic, the microprocessor
propagates the sign bit through the high order half of the 16-bit register
holding the 8-bit value – a process called sign extension
or sign propagation.
Computer science
Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...
, the sign bit is a bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
in a computer numbering format that indicates the sign
Sign (mathematics)
In mathematics, the word sign refers to the property of being positive or negative. Every nonzero real number is either positive or negative, and therefore has a sign. Zero itself is signless, although in some contexts it makes sense to consider a signed zero...
of a number. In IEEE format, the sign bit is the leftmost bit (most significant bit
Most significant bit
In computing, the most significant bit is the bit position in a binary number having the greatest value...
). Typically if the sign bit is 1 the number is negative (in the case of two's complement
Two's complement
The two's complement of a binary number is defined as the value obtained by subtracting the number from a large power of two...
integer
Integer
The integers are formed by the natural numbers together with the negatives of the non-zero natural numbers .They are known as Positive and Negative Integers respectively...
s) or non-positive (for ones' complement integer
Integer
The integers are formed by the natural numbers together with the negatives of the non-zero natural numbers .They are known as Positive and Negative Integers respectively...
s, sign-magnitude integer
Integer
The integers are formed by the natural numbers together with the negatives of the non-zero natural numbers .They are known as Positive and Negative Integers respectively...
s, and floating point
Floating point
In computing, floating point describes a method of representing real numbers in a way that can support a wide range of values. Numbers are, in general, represented approximately to a fixed number of significant digits and scaled using an exponent. The base for the scaling is normally 2, 10 or 16...
numbers), while 0 indicates a positive number.
When an 8-bit value is added to a 16-bit value using signed arithmetic, the microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
propagates the sign bit through the high order half of the 16-bit register
Processor register
In computer architecture, a processor register is a small amount of storage available as part of a CPU or other digital processor. Such registers are addressed by mechanisms other than main memory and can be accessed more quickly...
holding the 8-bit value – a process called sign extension
Sign extension
Sign extension is the operation, in computer arithmetic, of increasing the number of bits of a binary number while preserving the number's sign and value...
or sign propagation.