Контрольные вопросы:

1. What is the function of a programming language?

2. What does the term ‘a programming language’ mean?

3. What are the elements of a programming language?

4. What does an implementation of a programming language provide?

TEXT III

COMPUTER-AIDED DESIGN

Computer-Aided Design (CAD) is the use of computer technology to aid in the design and particularly the drafting (technical drawing and engineering drawing) of a part or product, including entire buildings. It is both a visual (or drawing) and symbol-based method of communication whose conventions are particular to a specific technical field.

Current Computer-Aided Design software packages range from 2D vector-bases drafting systems to 3D solid and surface modelers. Modern CAD packages can also frequently allow rotations in three dimensions. Allowing viewing of a designed object from any desired angle, even from the inside looking out. Some CAD software is capable of dynamic mathematic modeling, in which case it may be marceted as CADD – computer-aided design and drafting.

Software technologies: Originally software for Computer-Aided Design systems was developed with computer languages such as Fortran, but with the advancement of object-oriented programming methods this has radically changed. Typical modern parametric feature based modeler and freeform surface systems are built around a number of key C (programming language) modules with their own APIs.

A CAD system can be seen as built up from the interaction of a graphical user interface (GUI) with NURBS geometry and/or boundary representation (B-rep) data via a geometric modeling kernel. A geometry constraint engine may also be employed to manage the associative relationships between geometry, such as wireframe geometry in a sketch or components in an assembly.

Today most Computer-Aided Design computers are Windows based PCs. Some CAD systems also run on one of the Unix operating systems and with Linux. Some CAD systems such as QCad, NX or CATIA V5 provide multiplatform support including Windows, Linux, UNIX and Mac OS X.

Computer-Aided Design is one of the many tools used by engineers and designers and is used in many ways depending on the profession of the user and the type of software in question. There are several different types of CAD. Each of there different types of CAD systems require the operator to think differently about how he or she will use them and he or she must design their virtual components in a different manner for each.

The Effects of CAD

Starting in the late 1980s, the development of readily affordable Computer-Aided Design programs that could be run on personal computers began a trend of massive downsizing in drafting departments in many small to mid-size companies. As a general rule, one CAD operator could readily replace at least three to five drafters using traditional methods.

Контрольные вопросы:

1. What does CAD (Computer-Aided Design) mean?

2. What are the most CAD-computers based on?

3. What are the main types of CAD?

4. What are the effects of CAD?

TEXT IV

DATABASE

A database is a structured collection or records or data that is stored in a computer system. The structure is achieved be organizing the data according to a database model. The model in most common us today is the relational model. Other models such as the hierarchical model and the network model use a more explicit representation of relationships.

Depending on the intended use, there are a number of database architectures in use. Many databases use a combination of strategies. On-line Transaction Processing systems (OLTP) often use a row-oriented datastore architecture, while data-warehouse and other retrieval-focused applications like Google’s Big Table, or bibliographic database (library catalogue) systems may use a Column-oriented DBMS architecture.

There are also other types of database which cannot be classified as relational databases.

Database management systems

A computer database relies on software to organize the storage of data. This software is known as a database management system (DBMS). Database management systems are categorized according to the database model that they support. The model tends to determine the query languages that are available to access the database. A great deal of the internal engineering of a DBMS, however, is independent of the data model, and is concerned with managing factors such as performance, concurrency, integrity, and recovery from hardware failures. In these areas there are large differences between products.

A relational Database Management System (RDBMS) implements the features of the relational model outlined above. In this context, Date’s “Information Principle” states: “the entire information content of the database is represented in one and only one way”.

Database models

Products offering a more general data model than the relational model are sometimes classified as post-relational. The data model in such products incorporates relations but is not constrained by the Information Principle, which requires that all information is represented by data values in relations.

Object database models

In recent years, the object-oriented paradigm has been applied to database technology, creating a new programming model known as object databases. These databases attempt to bring the database world and the application programming world closer together, in particular by ensuring that the database uses the same type system as the application program. This aims to avoid the overhead (sometimes referred to as the impedance mismatch) of converting information between its representation in the database.

Database storage structures

Relational database tables/indexes are typically stored in memory or on hard disk in one of many forms, ordered/unordered flat files, ISAM, heaps, hash buckets or B+ trees.