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.