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Concepts of Information Processing

People have always needed to count. Earlier they counted with their fingers and probably through scratch markingson trees or bones or on the walls of their caves. People are now able to solve very sophisticated problems, andincreasingly so with the aid of computers.

Today we use computers in virtually every environment, even in areas unconnected with number manipulation.

What is Data ?

Data is a collection of facts, figures, statistics which can be processed to produce meaningful information.

What is Processing ?

Processing is the manipulation of the letters, numbers of graphic symbols that constitute data. Data is collected,captured, shifted, rearranged, sorted in sequence, stored, retrieved, formatted and sent to various persons whoneed the information

Processing includes -Calculation : addition, subtraction, multiplication, divisionComparison : equal to, greater than, less than, zero, positive, negativeDecision-making : branching to a different path depending on a conditionLogic : the sequence or flow of step to be followed to get the desired result

What is Information ?

Information is processed data. It refers to facts, figures or statistics that have meaning. Although data andinfomation are technically different they are often used interchangeably.

What is a Computer ?

A computer is often understood to be a device that computes or calculates numbers. It can be defined as anelectronic device with the ability to

1. Accept data supplied by the user 2. Input, store and execute instructions3. Perform mathemtical and logical operations4. Output results according to user requirements

Functional Components of a Computer

Central Processing Unit (CPU)

The hardware of any computer system can be broadly classified into the Central Processing Unit (CPU) and theperipherals.

The heart of the computer is called the CPU (Central Processing Unit) or processor. The CPU performs :

Arithmetic operations: addition, subtraction, multiplication, divisionLogical operations: logical comparisonsInput - output operations : accepting data to be processed, generating the output or results of processingInternal data movements : moving data between various parts of storageData manipulation : accepting data, sorting it, processing it, generating the required information

To perform these various operations the CPU has various components

1. Arithemetic-logic unit (ALU)2. Control Unit (CU)3. Memory Unit

Arithmetic Logic Unit (ALU) performs the actual calculations (add, subtract, divide, multiply) and comparison(greater than, lesser than, equal to, positive, negative, zero).

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Arithmetic Logic Unit (ALU) performs the actual calculations (add, subtract, divide, multiply) and comparison(greater than, lesser than, equal to, positive, negative, zero).

Control Unit (CU) coordinates the operations of the hardware. It also coordinates the flow and execution of dataand instructions that are fed into the memory or main storage via the CPU. The CU functions in a fetch-executecycle. It fetches the instructions and data from the memory unit, decodes them and sends them to the ArithmeticLogic unit (ALU). The output from the ALU is fetched by the control unit and sent to various parts of the computer.

Memory unit or Main store hold data instructions (that are being interpreted and executed), intermediate resultsand final results ready for output. The data and instructions are passed from the main store into ALU, or to and fromthe storage devices under the control of the CU. All instructions or data are stored in the memory unit before beingused by the ALU, or the CU . The main store is divided into a number of storage locations. These locations can beaccessed by a unique number or address.

Within the CPU are a number of high speed, special purpose memory units called registers. These registers carryout critical functions in the execution of programs. A computer has four basic types of registers:

1. accumulator register (ACC)2. store operand register (SOR)3. control register (CR)4. instruction address register (IAR)

Data Storage Devices

RAM

Typically semiconductor elements are used in primary storage sections or main memory. Semiconductor storage

elements are small integrated circuits. The storage cell circuits and the support circuitry needed for reading andwriting data are packaged on chips of silicon. Chips that use metal-oxide semiconductor (MOS) technology areusually used in the primary storage section. The components are called random access memory (RAM) chips. It ispossible to read from and write to any location within RAM by specifying its location or address. New data can bewritten onto any location, however, while doing so the previous existing data is erased.

RAM chips may be classified as :

1. dynamic2. static

Dynamic RAM chips - The storage cell circuits contain

a transistor (functions like mechanical on-off light switch) a capacitor used to store an electric charge

Depending on the switching action of the transistor, the capacitor may have no charge (0 bit) or hold a charge.(1

bit). The charge on the capacitor must be periodically refreshed or recharged. I the event of power loss dynamicRAM loses its contents. It is thus called volatile storage.

Static RAM chips - are also volatile storage devices. However, as long as they are supplied with power, they do notrequire special regenerator circuits to retain the stored data. More transistors and other devices are needed to storea bit in static RAM. These chips are more complicated than dynamic RAMs. Static RAMs are used in specialisedapplications. Dynamic RAMs are typically used on the primary storage section.

ROM

There are certain essential functions that the computer must perform when it is switched on (e.g. establishingconnections within the various components of the computer and its peripherals). These low level or machine levelfunctions are carried out through a series of programs or microprograms. These microprograms are stored on chips.These Read Only Chips (ROM) contain data which can be read randomly when required but cannot be written onto.

Data is hardwired onto these chips at the time of manufacture. They cannot be changed by the user.

While both RAM and ROM are storage devices and can be accessed randomly, they differ in that data can bewritten onto RAM while ROM does not permit the user to write onto it.

ROM retains the data in it even in the absence of power and is thus non-volatile storage.

PROM

Short for programmable read-only memory, a memory chip on which data can be written only once. Once a programhas been written onto a PROM, it remains there forever. Unlike RAM, PROMs retain their contents when thecomputer is turned off.

The difference between a PROM and a ROM (read-only memory) is that a PROM is manufactured as blankmemory, whereas a ROM is programmed during the manufacturing process. To write data onto a PROM chip, youneed a special device called a PROM programmer or PROM burner. The process of programming a PROM issometimes called burning the PROM.

EPROM

An EPROM (erasable programmable read-only memory) is a special type of PROM that can be erased by exposingit to ultraviolet light. Once it is erased, it can be reprogrammed.

EEPROM

EEPROM stands for Electrically Erasable Programmable Read Only Memory. EEPROM data cannot be selectivelyrewritten; the entire chip must be erased and rewritten to update its contents.

While Random Access Memory (RAM) loses its data every time you power down your computer, EEPROM does


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disk, which allows convenient storage and faster access than on magnetic tape. Data however, must be retrievedsequentially.

Types of Processing Systems

There are variety of processing options available today.

1. Batch processing systems2. On-line systems3. Real-time systems4. Distributed systems

Source ---Freepedia


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