Information System Literact Concepts by Hossein Bidgoli

Information System Literact Concepts by Hossein Bidgoli

we Define computers as a machine that accepts data as input , processes the data without human

interference using a set of stored instructions, and outputs information.

Computer programs consist of instructions written in a language understood by computers.

Data is raw facts and information is processes fact.

Types of processing

In Batch Processing, data is sent to the computer periodically, for example, every 24 hours,

every two weeks, or every month. Payroll is a good example where the data is not needed immidietly.

Transaction Processing required when data need immidiete response.

Disk Drives

Disk drives are used to read and store data or information from and to the disk in the main 

memory.

Main Memory/RAM

It is reffered to as RAM(Random Access Memory). This is a volatile memory. It will be lost

in event of power failure.

Since the main memorty of a microcomputer is limited , expensive and volatile, secondary storage

is used for mass storage.

Secondary storage devices are broadly classified as magnetic and optical.

Magnetic Storage Devices

Optical disks use laser beams , highly concentrated beams of light, to access and store data.

This technology can store vast amount of data. However, because optical technology is relatively

new, it is expensive.

An operating system is a set of programs that control and supervises computer hardware and 

software.

An operating system provides an interface between a computer and a user. It typically resides in

the main memory. A typical OS consists of two sets of programs: control programs and supervisor

programs.

Control Program manage the computer hardware and resources, including job management, resource

allocation, data management and data communication.

CS 2

File Structures

Index file--Uses Index concepts

Hashed files represent a file storage system that provides direct access only, without the 

overhead encountered with index maintenance.

Distributed database-- a database spread over several machines in a network.

The Commit Protocol

The point at which all the steps in a transaction have been recoreded in a log is called commit

point.

Basic overview of Computer Science -- Definitions and Stuff

An algorithm is a set of steps that define how a task is to be performed.

Programs are collectively called software in contrast to machinery itself which is called hardware.

Intellgence required to perform a task is in algorithm.

A flip flop is idle for storage of bit within a computer. The value stored in the flip-flop can

be placed on a single wafer(called a chip) no larger than a dime.

Throughput is a better word to use than execution speed.

Throughput refers to total amount of work the machine can accomplish in a given amount of time

rather than how long it takes to execute one task.

The task of memory manager is complicated further when the total main memory space required 

exceeds the space available in the machine.In this case, the memory manager can create illusion

of additional memory space by rotating the programs and data back and forth between main memory and

storage.

The term worm normally refers to an autonomous program that transfers itself through a network,

taking up residence in machines and forwarding copies of itself through the network. 

The rules that govern the communication between components are called protocols.

Lexical Analysis is the process of recogonizing which strings of symbols from the source program 

represent a single entity. For Example, the three symbols 153 should not be interpreted as a 1

followed by 5 followed by a 3 but should be recogonized as representing a single numeric value.

Parsing is the process of identifying the grammatical structure of the program and recogonizing 

the role of each component.

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