What is the ALU in Computer: functions and ALU Full Form, Define ALU

Friends, today we are going to go about ALU, what is its function in a computer, how does it work, why is it so special for a computer, how does it work with CPU and many other important things that we need to know. Many people in my block asked about this so I thought that an article should be written on it in detail and I hope you will like the post because this article is going to increase the knowledge.

What is the ALU in Computer: functions and ALU Full Form, Define ALU

History of ALU in Computer

The earliest electronic computers were developed

For providing the arithmetic engine in the 1940s

Solve a variety of problems, many of them army.

Computers, as Common Symbol Manipulators, Now

Solve other amusing problems, but numerical cacula-

The computer is still of vital importance in Apple-

cations. How Computers Store Numbers and Displays

Arithmetic and how computer differs from arithmetic

Simple hand calculations are the subject which should be

Understood by all who use computers.

Introduction ALU

An arithmetic unit, or Arithmetic Logic Units (ALU) enables a computer to perform mathematical operations on binary numbers. They can be found at the heart of every digital computer and are one of the most important parts of the CPU (Central Processing Unit). This note explores his original work, anatomy, and history. This makes the arithmetic unit easier.

Most of a CPU's operations are performed by one or more ALUs, which load data from input registers. A register is a small amount of storage available as part of the CPU. The control unit tells the ALU what operation to perform on that data and the ALU stores the result in an output register. The control unit moves data between these registers, the ALU, and the memory.

Arithmetic logic unit (ALU) is a digital circuit used to perform arithmetic and logic operations. It represents the fundamental building block of the Central Processing Unit (CPU) of a computer. Modern CPUs have very powerful and complex ALUs. In addition to the ALU, modern CPUs have a control unit (CU).

 Modern CPUs have extremely powerful and complex ALUs. The ALU keyline is a unit (CU) in modern CPUs.

Anatomy of an Arithmetic Unit & ALU

In its simplest form, an arithmetic unit can be viewed as a simple binary calculator - performing binary addition or subtraction on two inputs (A and B) to output the result.

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Simple ALU

a simple arithmetic unit

As well as performing basic mathematical operations, the arithmetic unit can also produce a series of 'flags' that provide further information about the state of the result: if it is zero, if it is a function, or if there is an overflow Has happened. This is important because it enables a computational machine to perform more complex behavior such as conditional branching.

However, modern computational machines have 'arithmetic units' that are far more complex than those described above. These units can perform additional basic mathematical operations (multiplication and division) and bitwise operations (AND, OR, XOR et al). As such, they are commonly referred to as ALU (Arithmetic Logic Unit).

Computer Storage of Numbers

Memory cell is the smallest unit of addressable

memory. old word-oriented computers

Usually larger cell sizes are used, such as 60 or 64 bits.

the new byte, or character, addressable computer

Address memory in smaller units called bytes.

 

computer oriented, a number is stored in a word,

Whereas in byte-oriented computers a number is stored. 2, 4, 8, and 16 bytes are commonly used in several bytes. "single-precision" numbers type-

32 bit storage (4 bytes) and "double-

precision" number occupies 64 bits (8 bytes).

A given number can be stored in one of two formats:

Fixed-point or floating-point. Fig. Shows 1 store-

Two-digit age, 0.15625 and 57.8125, as determined—

Digit number in 32-bit format. During this

Numbers in text, text will be quoted in decimal but

Their stored representations will be shown in binary.

For convenience . Only positive numbers will be used in

Examples. The collection of negative numbers can be either. The binary point is always at the same, fixed position.

Hence it was named "fixed point".

Processors employ different AUs for different classes.

This should be described in the full discussion of the ALU

Three fundamental properties:

1. Operations and Results

2. Functional Organization

3. Algorithms

Operations and Results

Two types of ALU organization can be distinguished

With respect to the length of machine words. in MA-

consist of all words, with fixed word length

Same number of bits. in variable word machines

The length is one byte.

Shortest machine word. consist of long machine words

Some integral number of bytes.

The operations and results of the ALU are machines

Two types of words: Arithmetic words, which denote-

send numeric values ​​in digital form, and logic words,

which represent an arbitrary set of digitally encoded

 (Traditional Radix Y Number Representation

Allow r values ​​for a single digit: 0, 1, . . . , r - 1. practical

Design considerations limit the choice of Radix

Up to the values ​​2, 4, 8, 10, and 16. value of each digit

Represented by a set of bits. Redis 2,4,8, and 16

1,2,3, and 4. employ binary numbers of length

Functional Organization

 Operation code identification-

Fails an operation from the set of available arithmetic

and also specifies the argument operation, and location

 The operand's designation is omitted in ALUs

with limited local storage; For example, an add operation-

The कोड code in a single-accumulator ALU always means

Adding Subsequent Operands to Operands

Accumulator register and storage of amount in

The accumulator format code is used when the ALU

can operate on more than one type of operand; For

For example, the ADD operation can be specified as either

Fixed-point or floating-point operands. Often, the operation-

ation code and format code a . is represented by

Single set of bits.

The output information given by the ALU includes

Result, status code and exception code.

The results are the machine words generated by the specified

operations and stored in local storage registers.

Condition codes are bits or sets of bits that identify the spec-

cic conditions associated with an outcome, such as

The value of the result is positive, negative, zero; That

The result contains all zeros, all ones, etc. except-

tion codes indicate that the specified operation is performed

do not give a representable result. Examples of except-

tions are overflow, i.e. the value of the result is higher

permissible limit; attempt to divide by zero; Apart from-

Massive loss of precision in floating-point operations; and

Error due to a logic fault. exception code usually

Set the flag bit in the machine status register.

Alu Algorithm

The operations are complemented in the circuit

(CP), Adder (AD), and Logic Operator Circuits

(take) Adder makes modulo a sum of addends

Increment in OPR and in Accl and return amount

Accl. When the length of the sum exceeds the stan-

Dard Word Length, Overflow Detection (OD) Circuit

Issues an overflow exception code, and extra digits

The amount is placed in an overflow digit position

(AOD), which is located at the left end of ACC 1.

Subtraction's complement is applied as

Subtrahend in OPR, followed by modulo A

for minuend in acc 1.

Left-shift and right-shift operations are performed

The words in the shift registers ACC1, ACC2, and MQR.

A single-shift operation displaces every digit in the reg-

iSter to the adjacent position on the left or on the right.

Shifts are specified for either an ACC register or

both acc registers with rightmost simultaneously

the position of acl around the position on the left

Acc2. There are three classes of shift:

1. Circular shift (rotation). right n

The leftmost positions of a register are considered as

adjacent during the shift.

2. Logical shift. Digits are discarded from the end posi-

tions and zeros are inserted; eg. during a

Right shift, right digit is lost and left-

Most of the position is filled with zeros.

3. Arithmetic Variation. purpose of an arithmetic

Shift is for multiplying (Shift left) or dividing (Shift)

right) operand by radix y for complement

Forms that represent negative numbers

Yo Times has been added to the content of ACC. then ACC1,

ACC2, and MQR registers shift arithmetically

one position to the right, and the next multiplier digit,

YL is realized by the MS circuit. After all n digits of Y

felt, the double-length product is xy

Located in the acl and acc2 registers. A roundoff operation-

Onion is needed to reduce the product to a single-word

Length. The algorithm for the integer x, y is described by

Arithmetic recurrence relation:

An alu can be bit-serial, byte-serial, or parallel, de-Pending on how many points are pending In the circuit of adder fig 2. In a serial alu, the adder adds a pair of digits at a time In a byte-serial alu, it combines a pair of two or more digits); In parallel alu, it connects two complete machine words. Variable word length machines byte-serial is alas, because one of the words is included different number of bytes. time required to complete An addition is a basic time unit in adder circuits.

Alu Operation.

Speed ​​of execution of algorithms in parallel Alu can be grown using various techniques.

Using more storage registers within Alu

Increases computing speed by reducing

Number of memory accesses. Therefore, 8, 16, or more Alu registers are often used instead of char.

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