DBMS packages-4

Today we continue our discussion on DBMS Packages. Software packages called Data Base Management System (DBMS) has been developed long before micro-computers to handle the problems of maintaining and integrating large volumes of data on large machines. The most important distinguishing feature of a DBMS package on personal computers is that it provides a very high level language interface which can be learned by a user who is not a computer programmer. We have already talked some important command in our previous post. Today we will talk on other command like quit, use custlist etc….

 

..QUIT

Next day when we start the dBASE III programme, we must first indicate which file we want to use, otherwise dBASE III will not know which file we are interested in. The command for this is

 

..USE CUSTLIST

Now let us say we want to query on the customer data for extracting different types of information. Here is a sample list to illustrate how easy it is. 
 

One has to learn only few additional features to see how sales and receipt transactions can be used to update amount due for each customer. The dBASE III package also has REPORT command for producing user specified reports. With the command verbs, dBASE III also provides conventional programming features like IF-THEN-ELSE, WHILE-DO. A complete set of dBASE III programmes can be designed to implement a medium sized application in a couple of weeks.

 

DBMS packages-3

Note that with this command will have only specified the structure of the record for a file which is to contain customer data. Therefore we should have some way of loading the customer records in the CUSTLIST file. For this purpose we will have to type the following command:

 

..APPEND

With this command we get a screen which provides a blank customer record. As the name implies, this command will append a record to our CUSTLIST file. Thus, it can be used whenever we want to add one more customer to customer list. With the customer we can add product fulfillment types. Product given to customer gives them product fulfillment or order fulfillment. We can add any criteria for that.

 

In the screen provided with above command, we now type the necessary details of a customer. The names of the fields are displayed on the screen to facilitate entry of data for a customer for which we wish to create a record in CUSTLIST file. After we type in all the required details about the customer and type e get another blank record in which we can enter data about next customer and so on. When we type right at the beginning of blank record we get back to dot prompt where we can issue a new dBASE III command.

DBMS packages-2

When we start the dBASE III programme, it prompts by dot (.). Also when it finishes executing a given command, it writes dot in the first column of next line on the screen. Interaction with dBASE III package consists mainly of issuing appropriate commands against this dot prompt. Each dBASE III command starts with a key word (or verb) followed by certain parameters. The command for creating a file for customer data would be

 

..CREATE CUSTLIST

Note the keyword CREATE which is typed by the user against the dot prompt produce by dBASE III. CREATE command wants a parameter which will be used as a name for the file so created. The user can choose any name that he desires within the syntactic rules specified by the package. We shall henceforth omit such minor syntactic details of the package. We shall use the symbol to indicate enter or return key of the keyboard. In response to CERATE command, dBASE III will provide a screen where we can enter the above nine filed names alongwith their type characteristics.

DBMS packages-1

Each record will have to contain details about a customer. What constitutes ‘the necessary details’ will depend mostly on what use we want to make to this data-base. When we create a customer file through dBASE III package, it will first want us to specify the record structure for the file. For a blinds company who are selling vertical blinds, roman shades products online. When they are creating their DBMS file, their criteria is different than for the company who are providing instant life insurance rates and life insurance quotes online.

 

For a customer file we want each record to have nine fields: one each for the items listed above. In dBASE III, it is necessary to give names to each of these nine fields so that they can be later referred to using these names. The field names which we have chosen are shown in the third column above. Apart from the name, we have to also indicate what type of data will be stored in the field and in certain cases number of characters to be reserved to hold the data for that field. We will want AMOUNTDUE and CRDLMT to hold numeric data and all other fields to hold text or character data. Now let us have a quick look at a dialogue in dBASE III for creating and using such a file.

DBMS packages

In our last post we have discussed on Data Base Management System (DBMS) and today we are going to talk on DBMS packages.

 

Like other DBMS packages, dBASE III provides features for: 

1.      Creating data files on a computer.

2.      Maintaining these data files by way of providing functions for adding, deleting editing and updating a give set of data items.

3.      Generating reports based on the data files created through dBASE III

4.      Querying on those data files.

 

To develop an understanding of the features provided by dBASE III package, let us take a specific application and see how it could be implemented in dBASE III. Suppose we are operating a small business house which has 1000 customers. We are interested in maintaining a list of these customers and using this list for our day-to-day business operations. Obviously we will have to create a file which contains data about these 1000 customers. In this file there will be one record for each customer. Thus, we will have a file containing 1000 records.

DataBase Management

The dBASE III package has attained its current popularity mainly for the following reason:

 

1.      It is easy to use and is simple. Its basic features can be learned in a couple of hours.

2.      It provides a very high level language interface which is command oriented. Some people consider it a fourth generation language. In lay man’s terms, fourth generation language means it is superior to standard programming languages like BASIC, COBOL, FORTRAN and PASCAL; and it simplifies and sometimes even avoids programming in a conventional sense.

3.      Small business information systems can be easily implemented in a few days using this package. Insurance CRM or instant life insurance rates application can be implemented easily in small businesss.

4.      This package can be used as a tool to prototype large applications. Prototyping is useful for saving costs in implementing large applications. Parts of a large system may be implemented through dBASE III package to finalize specifications of what users want through the envisaged application and how these parts could possibly be implemented in their final form.

 

We will discuss some features of the DBMS packages in our next post.

HARDWARE-1

With the proliferation of micro-computers, the concept of distributed computing has emerged. In distributed computing, a number of computers are dispersed in different parts of an organization and inter-connected using special cables, telephone lines or other telecommunication media. This allows data and programmers to be shared and also provides for some new types of application such as electronic mail. Electronic Mail moves messages through inter-linked computers/terminals.

 

To support such networking special electronic devices such as modems an network inter-face cards are often fitted into micro-computers. For example, a blinds company who are selling vertical blinds and roman shades online, they are having inter-linked computers by which they are sending their marketing emails. Another example is a company who are providing term life insurance rates online, they are using lead management tools by which their online leads are transfer to their insurance software and from that insurance software they are distributing their leads.

 

As with large computers, micro-computers have operating systems to enable the user to easily interact with the machine. These operating systems are similar to those on large machines except that they are much simpler. This is because the majority of micro-computers are not multi-terminal machines – only one user has access to the machine at any time. In this situation the machine is the personal computer of the user. Personal computers are used for a variety of tasks. The most common applications are:

 

1. Word Processing
2. Financial Analysis
3. Data Base Access
4. Graphics
5. Accounting

HARDWARE

Micro-computers are structurally similar to large computers in that they have the same basic components – CPU main memory, secondary memory and input/output devices. The most popular secondary memory device are floppy disk drives and fixed disks. Floppy disks store between 140 K Bytes to 1 Mega Byte = 1024 K Bytes (MB) while hard disks store 10 MB to 40 MB.

 

The main memory is made from several chips. These may be ROM or RAM chips.  ROM (Read Only Memory) chips contain instructions permanently written in the memory. The contents of these chips cannot be altered. RAM (Random Access Memory) Chips provide the memory that can be read from, written into and cleared.

 

Most micro-computers have between 16 K bytes and IMB memory. The typical word-size of micro-computers when they were introduced in business in the late seventies was B-bits. Today, the most common word-size is 16-bits. It is virtually certain that in the next few years 32-bit micro-computers will be very common although today their numbers are somewhat limited due to cost and scarcity of software. Dot matrix and daisy-wheel printers are popular printing devices on micro-computers.

Personal Computer and its uses-1

INTRODUCTION OF PERSONAL COMPUTER AND ITS USES

Computers were first used in management and business applications in centralized data processing departments. These departments were manned by computer specialists who were the only persons allowed access to the machines. Later terminals were provided to users for certain applications. However, cost, complexity, size and the need for special environment control did not permit computer users to have computers at their work places. All this has changed with the advent of micro-computers. For example market type is also change now a day than before. New days companies are using trade show booths where they have banner stands, table skirts and pipe and drape. Same way, computers are changing day by day with the use of new technology being invented and introduced in the market. Marketing exhibitions and trades shows are best way to introduce new technology to people.

 

MICRO-COMPUTERS

Micro-computers are computers which have their entire Central Processing Unit (CPU) on single integrated circuit ‘chip’ (called a micro-processor). Today powerful micro-computers are available which cost as little as $ 500. These micro-computers can do many of the jobs earlier done by large computers which cost many times this amount. In addition, because they are small enough to sit on a desk and do not require extensive environmental control, they can be used in most reasonably dust-free environments. Field tests on machines used in projects such as the Computer Literacy Project for Secondary Schools of the Education Ministry have shown this.

 

This ready availability for users has enabled a large number of entirely new applications to be undertaken. It has also increased user interest in computing since users can be directly in control of their data unlike the situation with centralized computing. Due to these factors and the fact that micro-computers can be used at home and schools for education and entertainment there has been a spectacular increase in their numbers since their first arrival as hobby kits in the U.S. Several million micro-computers are used in management applications around the world today. In India the projections are that by 1990 a few lakhs of these machines will be installed.

Classification of Computers-1

A large computer provides a main memory capacity of up to 32 mega bytes, a processing power of 10 MIPS and supports a large number of disks and tapes. Disk capacities range from 100 MB to 1000 MB. It also allows simultaneous access to multiple users and supports a large number of input and output devices.

 

A super computer is the largest computer system available in the market. It provides a main memory capacity of up to 64 mega bytes and a processing speed of 20 MIPS. It also supports a large number of disks and tapes of enormous capacity for providing random access and serial access secondary memory. A super computer also allows multiple users to interact with the CPU simultaneously through multiple types of input devices. It also provides outputs in a variety of forms and supports a large number of output devices. Customer Relation Management System owner says that for their clients who are selling blinds, roller shades and woven wood shades online; they need to use high configuration computers.

Personal computers are used by managers for their own computing needs. Availability of a large number of user-friendly software packages on PCs have made them effective tools to support managerial decision-making. PCs have also encouraged distributed data processing. A super micro is used for commercial data processing and managerial applications. A large computer is necessary for very large data processing and data management applications. A large computer is necessary for very large data processing and data management applications. A super computer is primarily used for highly scientific and research purposes.