Computer Links

A computer is a machine which helps us to calculate, simulate and store different scenarios. For example, in order to write an e-mail, instead of paper and pen first we use a software (or program) called wordprocessor which helps us enter sentences through keyboard (Input), computer's screen (output) to read, and modem (output/input) to send it to a distant relative, friend, etc.

The mechanism to simulate a regular mail into an e-mail, gave us a very fast and much cheaper medium to communicate (not a simulation anymore). Same way, using computers we can simulate other things over which we do not have any control, for example weather, behaviour of atomic bomb, behaviour of a deadly virus, Earthquake, a innovative design for a new auto, airplane, machine, etc.

Any computer has five parts Input, Output, CPU, Memory, disk (storage) . Input is things like mouse, keyboard, modem. Output is computer screen, printer. CPU or central processing is brain of the computer which controls and execute all calculations, manipulations and output. Memory (RAM)is a temporary storage to be used by CPU when doing calculations, etc. Think of it as a scratch pad for CPU. Disk is permanent storage, on which all the software and data is stored.

A database is a software which lets user to organize their data in an orderly fashion. For example consider a company which sells cookies, they have a database of which has tables (or records) of customers, types of cookies and orders. So when customer x orders n number of x type of cookies his orders is placed in table orders. There are several type of databases. Some which are simply text files with records, others which are complex with tables of information. A table of information means "an array of one type of records", for example "an array of customer names, addresses, phone numbers". A Relational database is in which there are relations among the tables, for example consider three tables with customer info, inventory info and orders info. The relations between these three tables define the relational database. So when a customer X from customer table orders Item Y from Inventory info it is put in Orders table, there are links in these tables (through primary keys, secondary and foreign keys such Social Security number, product number, order number, etc) which lets us do that and thus making it a relational database. Popular type of relational databases are Access for PCs on windows 95, Oracle, Sybase, Informix, for huge business environment (running Unix operating systems).

Internet is a bunch of computers connected to each other. It started out when about 10 computers running Unix operating systems serving US military were connected to each other and named ARPANET. Initially, users could only send an e-mail to each other, deploying UUCP (unix to unix copy using modems) method. Then more computers from universities were added to ARPANET and research individuals started sharing their notes over e-mail. Later came Usenet which was more or less a discussion forum. Then after tremendous innovations in hardware (networking), in 1992 came Web, or the software called web browser which could display pictures and text. REST is history. Some terms

• HTML : is Hypertext markup language. All pages in Internet use HTML.
• Browser is piece of software to browse internet, i.e Netscape, Internet explorer.
• Router is a piece of hardware which connects LAN to Internet.
• Bridge is a piece of hardware which connects two LANs.

Programming languages are designed to aid humans to write code for computers. Since computers only understand the language of o's and 1's, and we humans a common english like languages, several computer languages were developed which translate code to computer language. Programming languages like C/C++,Visual Basic, Java using these a person writes a code and then compiles it and creates an executable file which is understood by machine. All .exe and .class files are executable files translated into language understood by computer.

Networking constitutes of connecting PCs and other machines with each other. If you have bunch of computers in same building connected to servers through several hubs it is a Local Area Network, like in an office building. If you have many buildings with many computers connected to each other it is a WAN or wide area network, like Universities. Going by same terminology Internet is probably Global Area Network. Servers are those computers which control user access to files, and are running all the time. All of the computers which are connected to Internet are servers since Internet demands access to information round the clock. When you use modem to connect to Internet on your Personal computer, you are connecting to a computer which is connected to Internet.

Operating systems are that piece of software which communicate with computer and converts all user commands back and forth. Operating systems have four parts which are Process manager, Memory manager, I/O manager and . Popular operating systems are Windows 95, Windows 98, Windows NT, Mac, SunOs, Digital, HP-UX, Solaris, Aix, etc.

Applications are the end user products which user run on a computer. i.e. Games, Word processing, excel, word, are all applications.

Personal computers are those machines that sit on your desk at home or at office, usually running Windows 95, MacOs, windows 3.1, windows 98, windows NT workstation, and other operating systems designed for PCs. Servers usually run more robust Operating systems like Unix, Windows NT, etc.