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

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.

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.

Classification Of Computers

 

In the 1970s computers were classified into three categories, namely, super-computers, large computers and mini computers. But the invention of the micro-processor which gave birth to micro-computers in the late 70s has drastically changed the computing scene. A wide range of computers are available today in the market ranging from a personal computer to a super computer.

 

A personal computer (PC) is a micro-computer which has its entire central processing unit on a single micro-processor chip. A PC provides a main memory capacity upto 640 kilo bytes and a processing power of 0.5 MIPS. It supports one or 2 diskette drives of 360 KB each for random access secondary memory. A PC usually comes with a standard key board, a visual display unit and a dot matrix printer. A PC is usually operated by a single user.

 

A super mico-computer has its entire central processing unit on a very powerful micro-processor, provides a main memory capacity of upto 16 mega bytes, has a processing power of 2 to 3 MIPS, supports Winchester disks of capacity 20 to 80 mega bytes and allows simultaneously access to multiple users. Today’s super micro is actually replacing yesterday’s mini computers which provide almost the same computing power it nit less, but based on a different technology.

Operating Systems-1

We are talking computers in management. We talked evaluation of computers and computer softwares in our previous talk. We talked about operating system in our last post, today we continue with that. We talked the drawback of idling the CPU was overcome with the introduction of overlapped processing.

For example why not take up input operation of job 2 and the output operation of job 1 simultaneously? This and similar considerations gave rise to the concept of multi-programming. A multi-programming operating system handles multiple jobs simultaneously by overlapping the input, output and processing cycles of various jobs.

This operating system was introduced along with third generation computers and is still very popular. It has replaced the earlier batch processing (serial) operating system. With multi-programming a CPU’s utilization is increased and hence jobs get executed faster on an average. However a multi-programming operating system is more complex hardware to support it.

Other types of operating systems which are popular today are multi-processing operating systems and real time operating systems. A multi-processing operating system uses multiple CPU’s to process multiple jobs. A real time operating system is a very different type of operating system, because it is used for different type of applications, i.e., real time applications such as airlines reservations, process control, etc.

Utilities

Utility programmes are those which are very often requested by many application programmes. mailing leads and marketing list are few example of such utility programmes which are used in large by industry. A few examples are:

SORT/MERGE for sorting large volumes of data and merging them into a single sort list like mortgage mailing list.

Transfer programmes for transforming contents from one medium to another, e.g., disk to tape, tape to disk, etc.

Operating Systems

An operating system is the most important system software and is required to operate a computer system. An operating system manages a computer’s resources very effectively, takes care of scheduling multiple jobs for execution and manages the flow of data and instructions between the input/output units and the main memory.

 

Operating systems became a part of computer software with the second generation computers. Since then operating systems have undergone several revisions and modifications in order to achieve a better utilization of computer resources. Advances in the field of computer hardware have also helped the development of more efficient operating systems.

 

The first operating system called batch processing (serial) operating system was developed for the second generation computers; This operating system executes jobs serially one after another from a batch of jobs submitted for execution. The central processing unit is kept busy only during the processing cycle of a job and it idles during the input and output operations.

 

The above drawback of idling the CPU was overcome with the introduction of overlapped processing. For example why not take up input operation of job 2 and the output operation of job 1 simultaneously? This and similar considerations gave rise to the concept of multi-programming. A multi-programming operating system handles multiple jobs simultaneously by overlapping the input, output and processing cycles of various jobs.

COMPUTER SOFTWARE

Today we are going to discuss on Computer Software part. This is a most important topic for Computers. Computer software consists pf sets of programmed instructions which enable the hardware units to perform. Programming a computer to perform has always been a very difficult task. The first electronic computer was programmed using wired panels. Today’s computers are programmed using software.

 

Computer software can be broadly classified into two categories – System Software and Application Software. System software is a set of instructions to the machine hardware to interpret and execute application software. Application software is a set of programming instructions for specific applications like payroll accounting, inventory control, etc. System software consists of language translators [called compilers (compiles program-wise), interpreters (compiles like-wise) and assemblers (converts semi-machine-language, macro-instructions, to machine language)], operating systems, utilities and special purpose software.

 

Computer software or just software is a general term used to describe a collection of computer programs, procedures and documentation that perform some tasks on a computer system. “Software” is sometimes used in a broader context to mean anything which is not hardware but which is used with hardware, such as film, tapes and records. 

We will discuss on languages translator in next post.

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