Explain what logic gates are, CU, ALU and memory?

Answer 1

Logic gate are simple electronic circuits which perform a function at the bit level. Typical gate functions are one of the following: AND, OR, NOT, XOR(exclusive OR)

Since gates work at the bit level the inputs and outputs of the gate are either 1 or 0 (TRUE or FALSE, YES or NO)

A NOT performs an inversion on a single bit, if it is TRUE then a NOT makes it FALSE.

Other gates may have two or more inputs
An AND requries that each input bit be TRUE in order for the output to become TRUE.
OR gates will have there output become TRUE if one or more of the inputs becomes TRUE.

Gates may be placed in various combinations to create more complex circuits.

CU
I assume you mean CPU stands for Central Processing Unit
this is the brains of the computer and is what directs binary words to and from memory and the ALU (Arithmetic Logic Unit) where simple math is done to a binary word. There are several types of memory.

Memory is classified several ways. Based upon its type such as ROM (Read Only Memory), RAM (Random Access Memory) ect. and its function such as a CACHE or REGISTER.

In a CPU individual memory locations are typically referred to as REGISTERS. REGISTERS hold information which the CPU & ALU are currently working with. The amount of registers available depend upon the design of the CPU

Answer 2

A logic gate is an elementary building block of a digital circuit. Most logic gates have two inputs and one output. At any given moment, every terminal is in one of the two binary conditions low (0) or high (1), represented by different voltage levels. The logic state of a terminal can, and generally does, change often, as the circuit processes data. In most logic gates, the low state is approximately zero volts (0 V), while the high state is approximately five volts positive (+5 V).

There are seven basic logic gates: AND, OR, XOR, NOT, NAND, NOR, and XNOR.

The AND gate is so named because, if 0 is called "false" and 1 is called "true," the gate acts in the same way as the logical "and" operator. The following illustration and table show the circuit symbol and logic combinations for an AND gate. (In the symbol, the input terminals are at left and the output terminal is at right.) The output is "true" when both inputs are "true." Otherwise, the output is "false."



AND gate

Input 1 Input 2 Output
0 0 0
0 1 0
1 0 0

1 1 1

The OR gate gets its name from the fact that it behaves after the fashion of the logical inclusive "or." The output is "true" if either or both of the inputs are "true." If both inputs are "false," then the output is "false."



OR gate

Input 1 Input 2 Output
0 0 0
0 1 1
1 0 1
1 1 1


The XOR (exclusive-OR) gate acts in the same way as the logical "either/or." The output is "true" if either, but not both, of the inputs are "true." The output is "false" if both inputs are "false" or if both inputs are "true." Another way of looking at this circuit is to observe that the output is 1 if the inputs are different, but 0 if the inputs are the same.



XOR gate

Input 1 Input 2 Output
0 0 0
0 1 1
1 0 1
1 1 0

A logical inverter, sometimes called a NOT gate to differentiate it from other types of electronic inverter devices, has only one input. It reverses the logic state.



Inverter or NOT gate

Input Output
1 0

0 1

The NAND gate operates as an AND gate followed by a NOT gate. It acts in the manner of the logical operation "and" followed by negation. The output is "false" if both inputs are "true." Otherwise, the output is "true."



NAND gate

Input 1 Input 2 Output
0 0 1
0 1 1
1 0 1
1 1 0

The NOR gate is a combination OR gate followed by an inverter. Its output is "true" if both inputs are "false." Otherwise, the output is "false."



NOR gate

Input 1 Input 2 Output
0 0 1
0 1 0
1 0 0
1 1 0

The XNOR (exclusive-NOR) gate is a combination XOR gate followed by an inverter. Its output is "true" if the inputs are the same, and "false" if the inputs are different.



XNOR gate

Input 1 Input 2 Output
0 0 1
0 1 0
1 0 0
1 1 1

Using combinations of logic gates, complex operations can be performed. In theory, there is no limit to the number of gates that can be arrayed together in a single device. But in practice, there is a limit to the number of gates that can be packed into a given physical space. Arrays of logic gates are found in digital integrated circuits (ICs). As IC technology advances, the required physical volume for each individual logic gate decreases and digital devices of the same or smaller size become capable of performing ever-more-complicated operations at ever-increasing speeds.

Answer 3

Just an addition to what others have answered,

CU

Control Unit acts like the supervisor seeing that things are done in proper fashion. The control unit determines the sequence in which computer programs and instructions are executed. Things like processing of programs stored in the main memory, interpretation of the instructions and issuing of signals for other units of the computer to execute them. It also acts as a switch board operator when several users access the computer simultaneously. Thereby it coordinates the activities of computer’s peripheral equipment as they perform the input and output. Therefore it is the manager of all operations mentioned in the previous section.

To know more info about Memory and other parts of computer, refer the site

Answer 4

LOGIC GATES
--------------------
A logic gate performs a logical operation on one or more logic inputs and produces a single logic output. The logic normally performed is Boolean logic and is most commonly found in digital circuits. Logic gates are primarily implemented electronically using diodes or transistors, but can also be constructed using electromagnetic relays, fluidics, optics, or even mechanical elements.

Different types of logic gates :

1)AND
The AND gate is a digital logic gate that implements logical conjunction - it behaves according to the truth table to the right. A HIGH output (1) results only if both the inputs to the AND gate are HIGH (1). If neither or only one input to the AND gate is HIGH, a LOW output results.

INPUT OUTPUT
A B A AND B
0 0 0
0 1 0
1 0 0
1 1 1

2)OR
The OR gate is a digital logic gate that implements logical disjunction - it behaves according to the truth table to the right. A HIGH output (1) results if one or both the inputs to the gate are HIGH (1). If neither input is HIGH, a LOW output (0) results.

INPUT OUTPUT
A B A OR B
0 0 0
0 1 1
1 0 1
1 1 1

3)NOT
The NOT gate or inverter is a digital logic gate that implements logical negation. It behaves according to the truth table to the right. A HIGH output (1) results if the inputs is LOW (0). If the input is HIGH (1), a LOW output (0) results.

INPUT
A OUTPUT
NOT A
0 1
1 0

4)NAND
The NAND gate is a digital logic gate that behaves according to the truth table to the right. A LOW output results only if both the inputs to the gate are HIGH. If one or both inputs are LOW, a HIGH output results.The nand gate is a universal gate in the sense that any boolean function can be implemented by nand gates.

INPUT
A B OUTPUT
A NAND B
0 0 1
0 1 1
1 0 1
1 1 0


5)NOR

The ""NOR gate"" is a digital logic gate that implements logical NOR - it behaves according to the truth table to the right. A HIGH output (1) results if both the inputs to the gate are LOW (0). If one or both input is HIGH (1), a LOW output (0) results. NOR is the result of the negation of the OR operator, thus forming a complete operation the combination of which can be combined to generate any other logical function. By contrast, the OR operator is monotonic as it can only change LOW to HIGH but not vice versa.

The nor gate like a NAND gate is an universal gate in the sense that any boolean function can be implemented by nor gates.

INPUT
A B OUTPUT
A NOR B
0 0 1
0 1 0
1 0 0
1 1 0

For more information visit:
http://en.wikipedia.org/wiki/Logic_gates

ALU
-----

The arithmetic logic unit (ALU) is a digital circuit that calculates an arithmetic operation (like an addition, subtraction, etc.) and logic operations (like an Exclusive Or) between two numbers. The ALU is a fundamental building block of the central processing unit of a computer.

Many types of electronic circuits need to perform some type of arithmetic operation, so even the circuit inside a digital watch will have a tiny ALU that keeps adding 1 to the current time, and keeps checking if it should beep the timer, etc...

By far, the most complex electronic circuits are those that are built inside the chip of modern microprocessors like the Pentium. Therefore, these processors have inside them a powerful and very complex ALU. In fact, a modern microprocessor (or mainframe) may have multiple cores, each core with multiple execution units, each with multiple ALUs.

Many other circuits may contain ALUs inside: GPUs like the ones in NVidia and ATI graphic cards, FPUs like the old 80387 co-processor, and digital signal processor like the ones found in Sound Blaster sound cards, CD players and High-Definition TVs. All of these have several powerful and complex ALUs inside.

For more information visit:
http://en.wikipedia.org/wiki/Arithmetic_logic_unit

CONTROL UNIT
--------------------

A control unit is the part of a CPU or other device that directs its operation. The outputs of the unit control the activity of the rest of the device. A control unit can be thought of as a finite state machine.

At one time control units for CPUs were ad-hoc logic, and they were difficult to design. Now they are often implemented as a microprogram that is stored in a control store. Words of the microprogram are selected by a microsequencer and the bits from those words directly control the different parts of the device, including the registers, arithmetic and logic units, instruction registers, buses, and off-chip input/output. In modern computers, each of these subsystems may have its own subsidiary controller, with the control unit acting as a supervisor. (See also CPU design and computer architecture.)

The control unit is the circuitry that controls the flow of information through the processor, and coordinates the activities of the other units within it. In a way, it is the "brain within the brain", as it controls what happens inside the processor, which in turn controls the rest of the PC.

The functions performed by the control unit vary greatly by the internal architecture of the CPU, since the control unit really implements this architecture. On a regular processor that executes x86 instructions natively, the control unit performs the tasks of fetching, decoding, managing execution and then storing results. On a processor with a RISC core the control unit has significantly more work to do. It manages the translation of x86 instructions to RISC micro-instructions, manages scheduling the micro-instructions between the various execution units, and juggles the output from these units to make sure they end up where they are supposed to go. On one of these processors the control unit may be broken into other units (such as a scheduling unit to handle scheduling and a retirement unit to deal with results coming from the pipeline) due to the complexity of the job it must perform

For more information visit :
http://en.wikipedia.org/wiki/Control_unit

MEMORY
------------

Computer storage, computer memory, and often casually memory refer to computer components, devices and recording media that retain digital data used for computing for some interval of time. Computer storage provides one of the core functions of the modern computer, that of information retention. It is one of the fundamental components of all modern computers, and coupled with a central processing unit (CPU), implements the basic Von Neumann computer model used since the 1940s.

In contemporary usage, memory usually refers to a form of solid state storage known as random access memory (RAM) and sometimes other forms of fast but temporary storage. Similarly, storage more commonly refers to mass storage - optical discs, forms of magnetic storage like hard disks, and other types of storage which are slower than RAM, but of a more permanent nature. These contemporary distinctions are helpful, because they are also fundamental to the architecture of computers in general. As well, they reflect an important and significant technical difference between memory and mass storage devices, which has been blurred by the historical usage of the terms "main storage" (and sometimes "primary storage") for random access memory, and "secondary storage" for mass storage devices. This is explained in the following sections, in which the traditional "storage" terms are used as sub-headings for convenience.

For more information visit :
http://en.wikipedia.org/wiki/Computer_memory


Hope this helps a little!!!!