Microprocessors

Jack Kilby at Texas Instruments invented the first monolithic integrated circuit in 1958. His device consisted of a bar of Germanium in which all the components were formed, but still required manual wiring of those components under a microscope.

Robert Noyce at Fairchild Semiconductor invented an improved monolithic integrated circuit about 6 months later. His device consisted of Silicon and using Fairchild's newly developed planar process allowed both components and wiring to be formed together. This process has been used for ICs ever since.

Federico Faggin at Intel invented the first commercial microprocessor IC, the 4004, in 1971.

Save time and/or money: In theory, throwing more resources at a task will shorten its time to completion, with potential cost savings. Parallel clusters can be built from cheap, commodity components.

Provide concurrency: A single compute resource can only do one thing at a time. Multiple computing resources can be doing many things simultaneously

Use of non-local resources: Using compute resources on a wide area network, or even the internet when local compute resources are scarce.

Limits to serial computing: Both physical and practical reasons pose significant constraints to simply building ever faster serial computers:

• Transmission speeds - the speed of a serial computer is directly dependent upon how fast data can move through hardware. Absolute limits are the speed of light (30 cm/nanosecond) and the transmission limit of copper wire (9 cm/nanosecond). Increasing speeds necessitate increasing proximity of processing elements.
• Limits to miniaturization - processor technology is allowing an increasing number of transistors to be placed on a chip. However, even with molecular or atomic-level components, a limit will be reached on how small components can be.
• Economic limitations - it is increasingly expensive to make a single processor faster. Using a larger number of moderately fast commodity processors to achieve the same (or better) performance is less expensive.

In magnetism:

An eddy current is induced into a metal when magnetic lines of force move across it. A South pole causes circulating current in clockwise direction while a North pole causes current in counter-clockwise direction. These eddy currents thus buck the applied forces. Eddy currents are undesirable when induced into transformer cores causing power loss. Lamination of core material reduces current flow in the core. Current induced into the secondary winding of a transformer is a used to step-up or step-down voltages so that they can be of a correct size for end-use applications.

<><><>

When time-varying magnetic field is applied to electrical machines like transformers, a time-varying emf is induced in the transformer cores. A short circuit occurs at the molecular level in the core. Due to less resistance, a large current begins to flow in the core. This causes heating in the core. Actually the path of the current is circular resembling the circular waves in a pool of water (eddy). Hence these currents are called eddy currents.

In fluids:

In water flow, an eddy is a current that flows opposite the normal flow. If on a river, an eddy is a current that will flow upstream in a side channel filling it, even if the flow is in an opposite direction of the original flow. It is equivalent to a stream's water level rising because the river it feeds has more water in it than the stream, thus making the water flow upstream. It can also be an area that seems not to have a current at all.

A:

Just like there exists a magnetic path due to current (charge) flow in a conductor (direction given by right hand rule), the thing works other way as well...

When there is a flux path crossing a current conducting material, there exists current paths around the flux line on the conductor plane centered to the point where flux line meets the plane. These currents are eddy currents.

Commonly available in magnetic circuits. Laminations are done to minimize the ability to flow eddy currents.

A computer can process data, pictures, sound and graphics. They can solve highly complicated problems quickly and accurately.

Input Unit:

Computers need to receive data and instruction in order to solve any problem. Therefore we need to input the data and instructions into the computers. The input unit consists of one or more input devices. Keyboard is the one of the most commonly used input device. Other commonly used input devices are the mouse, floppy disk drive, magnetic tape, etc. All the input devices perform the following functions.

• Accept the data and instructions from the outside world.
• Convert it to a form that the computer can understand.
• Supply the converted data to the computer system for further processing.

Storage Unit:

The storage unit of the computer holds data and instructions that are entered through the input unit, before they are processed. It preserves the intermediate and final results before these are sent to the output devices. It also saves the data for the later use. The various storage devices of a computer system are divided into two categories.

1. Primary Storage: Stores and provides very fast. This memory is generally used to hold the program being currently executed in the computer, the data being received from the input unit, the intermediate and final results of the program. The primary memory is temporary in nature. The data is lost, when the computer is switched off. In order to store the data permanently, the data has to be transferred to the secondary memory.

The cost of the primary storage is more compared to the secondary storage. Therefore most computers have limited primary storage capacity.

2. Secondary Storage: Secondary storage is used like an archive. It stores several programs, documents, data bases etc. The programs that you run on the computer are first transferred to the primary memory before it is actually run. Whenever the results are saved, again they get stored in the secondary memory. The secondary memory is slower and cheaper than the primary memory. Some of the commonly used secondary memory devices are Hard disk, CD, etc.,

Memory Size:

All digital computers use the binary system, i.e. 0's and 1's. Each character or a number is represented by an 8 bit code.

The set of 8 bits is called a byte.

A character occupies 1 byte space.

A numeric occupies 2 byte space.

Byte is the space occupied in the memory.

The size of the primary storage is specified in KB (Kilobytes) or MB (Megabyte). One KB is equal to 1024 bytes and one MB is equal to 1000KB. The size of the primary storage in a typical PC usually starts at 16MB. PCs having 32 MB, 48MB, 128 MB, 256MB memory are quite common.

Output Unit:

The output unit of a computer provides the information and results of a computation to outside world. Printers, Visual Display Unit (VDU) are the commonly used output devices. Other commonly used output devices are floppy disk drive, hard disk drive, and magnetic tape drive.

Arithmetic Logical Unit:

All calculations are performed in the Arithmetic Logic Unit (ALU) of the computer. It also does comparison and takes decision. The ALU can perform basic operations such as addition, subtraction, multiplication, division, etc and does logic operations viz, >, <, =, 'etc. Whenever calculations are required, the control unit transfers the data from storage unit to ALU once the computations are done, the results are transferred to the storage unit by the control unit and then it is send to the output unit for displaying results.

Control Unit:

It controls all other units in the computer. The control unit instructs the input unit, where to store the data after receiving it from the user. It controls the flow of data and instructions from the storage unit to ALU. It also controls the flow of results from the ALU to the storage unit. The control unit is generally referred as the central nervous system of the computer that control and synchronizes its working.

Central Processing Unit:

The control unit and ALU of the computer are together known as the Central Processing Unit (CPU). The CPU is like brain performs the following functions:

• It performs all calculations.

• It takes all decisions.

• It controls all units of the computer.

A PC may have CPU-IC such as Intel 8088, 80286, 80386, 80486, Celeron, Pentium, Pentium Pro, Pentium II, Pentium III, Pentium IV, Dual Core, and AMD etc.

The crystal frquency in an 8085 system is twice the desired clock frequency, so a crystal of 2.2 MHz is required to operate at 1.1 MHz.

Note: Clock frequency is not the same as instructions per second, because the instructions in an 8085 take a variable number of clock cycles, between 4 and 18, to execute.

The socket API is an Interprocess Communications (IPC) programming interface;Originally provided as part of the Berkeley UNIX operating system (1980);It is a de facto standard for programming IPC;Adopted by many modern operating systems, e.g. Sun Solaris and Windows systems;Underlying service for sophisticated IPC, e.g. RPC, RMI, CORBA, Web Services, etc.

A socket API provides a programming construct termed a socket;A process wishing to communicate with another process must create an instance, or instantiate, such a construct;The two processes then issues operations provided by the API to send and receive data Also in case of Java, Datagram sockets can support both connectionless and connection-oriented communication at the application layer. This is so because even though datagrams are sent or received without the notion of connections at the transport layer, the runtime support of the socket API can create and maintain logical connections for datagrams exchanged between two processes, as you will see in the next section.

In computer programming, a loop is a series of instructions given and carried out continuously until a condition is made or an error is found. Both of these possibilities come to the same result, termination of the loop unless the program is specified to run for an infinite amount of time.

EXAMPLE:

#include int main() { int i; for (i = 0; i < 10; i++) { printf ("Hello\n"); printf ("World\n"); } return 0; }