Operating system interfaces. Graphical interface of operating systems Graphical interface tools for users of various operating systems

Any device, mechanical or electronic, whose tasks include direct interaction with the user, in addition to its internal filling, must have something thanks to which this very interaction could be carried out. The name of this intermediary is known to everyone today. This is the interface. It can be analog, but usually the interface is understood as a graphical shell or otherwise GUI operating systems and software.

Most interfaces of today's popular operating systems are characterized by an intuitive graphic design using visual effects, but this was not always the case. From the point of view of a modern user, the first GUI were quite primitive, although, to their credit, this did not always mean a lack of quality for those times usability.

A little background

Traditionally year of birth GUI it is generally accepted 1973 , it was then that the first personal computer in the full sense of the word was born, which used a graphical interface, but it would be unfair not to mention its earlier predecessors. IN 1962 year scientist Ivan Sutherland a program was created that can be considered the first prototype of graphic editors.

It was called and allowed you to draw figures on the screen with a light pen. Six years later, scientists at the Stanford Institute presented the first graphical interface computer system oN-Line System, which already then contained the concept of modern windows, a mouse and hypertext links. But oN-Line System was rather a demonstration of the technical capabilities of that time, while remaining very primitive.

Xerox - the first true GUI

It is more correct to consider the ancestor of all currently existing graphical interfaces GUI , developed as part of the project - the first personal computer created in 1973 year. Shell was very simple, but even then it had menus, buttons and primitive windows. It also included a mouse cursor with its inherent functions of selecting, copying and pasting.

Further more. IN 1981 year a new system appears called, based on the same , but with more advanced functionality and graphical interface. You might be surprised, but the desktop not much different from current desktops, unless, of course, you take into account the visual effects.

It is based on the same principle of using shortcuts to launch files and navigate through directories in the file system.

Apple - first steps, observed in Xerox Lab

It must be said that it was not the only operating system at that time. At first 80 's companies presented their developments to the world Apple And Microsoft . Understanding all the meaning GUI , but not having enough time to create original shells for their systems, the developers of both companies borrowed ideas Xerox Lab, which subsequently even led to a conflict between Steve Jobs And Bill Gates. Jobs accused Gates of plagiarism for allegedly copying the interface from Macintosh.

Of course, Steve was wrong, because both he himself and Gates, who he accused, took the concept GUI at Xerox Lab, it just so happened that Jobs was the first, and if you compare the interfaces , as well as related Macintosh, then you can see a clear similarity with . If there is anything new that the company has added, it is a text menu at the top of the desktop, the Recycle Bin and a number of shortcuts, whose appearance, according to "apple" designers, was more consistent with the purpose of the programs and functions launched through them.

DOS. Norton Commander as an attempt to create an original GUI

Borrowing ideas Xerox Lab, however, does not mean that no attempts were made to create original interfaces for operating systems. IN 1986 year programmer John Socha was created - a file manager for MS-DOS, which previously had virtually no graphic design. The role of windows in it was played by panels dividing the screen vertically and containing lists of folders and files. At the top and bottom of the manager there were text menus that allowed you to perform certain operations.

However, GUI in the full sense of the word didn't show up. Like the one released in 1988 year its analogue, it refers to pseudo-graphical interfaces that imitate graphics while remaining text-based.

However, both of these applications made working with data much easier by eliminating the need for users to enter DOS -teams, which has been the reason for the popularity of these programs for a long time.

After leaving the development team, 1982 year Steve Jobs headed his own project Macintosh. The system developed for Macs was called Mac OS. Outwardly, it was similar to the Apple Lisa, but it also had unique features that were unique to it, and they concerned both the appearance of the interface elements and the user’s interaction with the shell. Like was based on the window principle, it used menus, icons and dialogs.

The shell made it possible to quickly rename files and folders, select them, copy them by dragging them to a destination, and close all windows at the same time, although closing windows did not always mean that the application was terminated; programs had to be closed correctly - through the main menu of the system. When closing edited but not saved files, a dialog box appeared asking for confirmation to save the changes or cancel them.

Mac OS 7.5.5

During the seven years of its existence Mac OS went through many changes, but almost all of them were minor and only in the seventh version did innovations appear that were worth mentioning. Perhaps the most important of them is color support, since before this the system interface was almost monochrome. Now the user could change the color of folder icons and some other elements, making them blue, yellow or red.

Present in a range of colors Mac OS 7.5.5 and other shades. At the same time it becomes colored "apple" logo on the left side of the main menu. Other changes include displaying module icons during system boot, expanding menu functionality, adding pop-up tips when hovering over options available in the menu, and implementing access to applications from a single control panel.

Mac OS 8.1

Work on the use of color in the graphical interface was actively continued in the eighth version of the system. System icons in Mac OS 8.1 were colored by default, and in the most OS a new application has appeared Appearance Manager, which allows you to control color schemes. acquired a set of background images; in addition, the user could set arbitrary pictures as backgrounds.

In the same edition, the famous platinum-gray theme appears for the first time, which later became the hallmark of all subsequent versions. Mac OS. Another interesting change was the application of isometrics to the icons, making them look like three-dimensional objects without actually being one. The settings for displaying the contents of the file system have been improved - files can now be viewed in the form of lists and icons, the size of which can also be changed.

Mac OS 9.2.2

Version 9.2.2 the story ends Mac OS based on the original operating system Macintosh and it seemed that it should have more innovations than previous versions. There are really a lot of changes in the ninth version, but they affected most of the functionality, while the interface changed slightly.

One of the most significant modifications that affected the graphical shell was integrated support for several accounts. When the system started, a profile selection window appeared on the screen, and each user could install their own themes, and third-party graphics packages were also supported. This version also improved the sound control panel and added the ability to set a voice password.

After leaving Apple, V 1985 year Steve Jobs founded his own company NeXT Computers, whose developers created OS NeXTSTEP . basis new system became the core Mach, and graphic design ideas were borrowed from Mac OS and earlier .

Like Mac OS, originally NeXTSTEP had a simplified monochrome interface based on the window principle using menus, icons and dialog boxes. Full color support appeared only in the version 3.3 , which became the last. From later versions Mac OS system featured a cleaner and more laconic design.

Microsoft Windows 1.0

We did not sit idly by and Microsoft. IN 1985 year the company presents its graphical shell for MS-DOS with a telling name Windows. The shell partially supported color graphics, it had 32×32-pixel icons, simple menus and dialogs. There was no fixed area in which icons of running applications would be displayed; they could be located anywhere on the screen, overlapping with open windows.

The windows themselves in the first version were quite primitive. They could be dragged with the mouse, their size could be changed, but at the same time they themselves could not overlap each other. It was also impossible to fold them. Interface Windows 1.0 made it easier to work with the system and files, eliminating the need for the user to enter commands in the console, but at the same time it lacked convenience. So in terms of usability the first Windows version significantly inferior to systems from Apple.

Microsoft Windows 3.11

Versions Windows 1.0 , 2.0 And 3.0 were not operating systems in the sense of the word in which it is commonly understood today. They were more like graphical shells MS-DOS, the first signs that set Windows apart OS, appeared only with the release of versions 3.1 And 3.11 , but they relate not so much to GUI , how much to functionality. In terms of graphic design, there were not so many significant changes.

IN Windows 3.11 There is already full support for colors, windows can overlap each other, they can be minimized and expanded. Slightly improved graphics individual elements (volumetric buttons and scroll bars) , proportional fonts are used, appearance programs File Manager And Program Manager implemented in the style of the shell itself. The user can change the colors of interface elements at his own discretion.

A true revolution in design Windows happened in 1995 year, it was then that the now familiar button appears in the system Start , Conductor , Task bar And desktop with icons , which at the same time was a separate folder. In the same version, display of disks in a folder was implemented "My computer" and a way to manage files from the menu called right click mice. An important innovation was the transition to 32 -bit architecture.

The history is also interesting Windows 95 and the role she played in the collapse of the project OS/2- operating system of a joint brainchild Microsoft And IBM. At the time of release Windows 3.0 disagreements arose between the companies. Microsoft sought to promote Windows, A IBM prioritized development OS/2. As a result, an agreement was concluded between the companies, according to which IBM should have been studying OS/2 2.0 And Windows 3.0, A Microsoft - OS/2 3.0.

However, the head Microsoft decided to do it his own way, declaring OS/2 2.0 outdated and newer OS/2 3.0 renamed to Windows NT. At the same time, Microsoft released Windows 3.1 and then an update for the version 3.1 under the code name Chicago , which forms the basis for the future Windows 95. After this path IBM And Microsoft finally separated. For a while IBM I was still developing OS/2, but the output is more competitive Windows 95 finally finished her off, and IBM was forced to cancel the project.

Since we touched on the topic of conflict between IBM And Microsoft, it would be unfair to ignore OS/2, the fruit of a once fruitful collaboration between both companies. After a quarrel and final break with Microsoft, developers IBM continued work on OS/2. In the version released in 1996 OS/2 Warp 4 Significant improvements have been made to the external design of the desktop and the graphical shell as a whole. There were icons on the desktop that provided access to various system settings, but they could also play the role of directories into which the user could place files and folders, was present Windows-similar taskbar and a single access menu to all programs.

OS/2 Warp 4 has a lot in common with Windows, but there are also very significant differences in it. Default drag and drop to OS/2 Warp 4 was carried out not with the left, but with the right mouse button, Basket was not used for temporary storage deleted files, but for their immediate destruction. Dialog boxes in this system had no buttons "Save" or "OK", data was saved automatically when the window was closed , unless the user canceled the action. Another interesting feature of the system was the ability to view the tree structure of the disk in windows.

DeskMate 3.05 (desktop version 3.69)

Exit Windows V 1985 year has not weakened interest in MS DOS, which continued to be popular, as well as the graphical shells created for it, including the one released by the company Tandy Wednesday DeskMate deserves special attention. DeskMate is not just a graphical add-on, it is a full-fledged operating environment that includes its own set of software.

Unlike , V DeskMate 3.05 there were full-fledged menus, buttons and some kind of windows that could be placed on a primitive desktop. The environment included a file manager with limited tree structure support, a built-in textbook, calendar, organizer, DBMS, text and vector graphic editors. Another distinguishing feature DeskMate 3.05 was support for primary colors.

AmigaOS- an operating system specially created for computers of the family Amiga V 1985 year. The interface of the first versions was something between a shell and pseudographic shells DOS, but already in windows appeared overlapping each other, colored icons for quick access to files, applications and disk drives.

Taken as a whole, has a lot in common with MacOS. The menu at the top of the screen shows options depending on which application is currently active, the windows are equipped with simple controls, and there are scroll bars. Distinctive feature AmigaOS is a function that allows you to work with multiple screens, and each screen could have its own resolution and color depth.

Small, fast and somewhat unusual Unix -like operating system developed for the platform Raspberry Pi . Externally it was distinguished by a minimalistic user interface, support for all resolutions available at that time for computers Acorn, drag-and-drop, it had windows, a kind of taskbar at the bottom of the desktop, colored icons and pseudo-3D decorative controls.

Its own features were single-user multitasking, modularity and a binary application interface, all files in it were volumes, applications were also implemented in the form of directories with exclamation point. Despite its minimalism, from the point of view of users accustomed to the environment Windows or LXDE, Desktop could seem inconvenient, since many of the control methods in it had significant differences.

BeOS 5.0PE

Quite a powerful operating system created by the company Be Inc . and multimedia-oriented. Originally developed for computers BeBox, but then switched to Macintosh, and then on PC. Story BeOS closely related to Apple, since the founder Be Inc. was none other than Jean-Louis Gassier- former executive director Apple. In addition to multithreading and support for multiprocessor architectures, the main feature BeOS 5.0PE was its interface, which had the features Windows and systems from Apple.

The system shell was distinguished by its well-thought-out usability and simplicity combined with elegance. As expected, it had windows, menus, and "team" a taskbar that resembles a similar shell element Windows, full-color icons and folders that could be placed on a minimalist-style desktop. Distinctive feature BeOS 5.0PE was the structure of the windows - instead of the traditional title bar, they used tabs located on top of the window.

Little known Canadian Unix -like system belonging to the type of so-called real-time operating systems. Being universal, it was distinguished by its high speed of operation and low demands on hardware resources. The graphical shell of the system is called Photon, but her desktop has a lot in common with a desktop Windows XP. At the bottom of the screen there is a horizontal control panel with something like a button Start and a vertical control panel on the right, changing background images is supported.

Window , in which applications are launched, have a similar structure to windows Windows. They can be collapsed and expanded, scaled, cascaded, etc. The conductor, as it is commonly understood in Windows V no, it is replaced by a file manager QNX Photon, similar in functionality to Windows Explorer. Thanks to its lightness, convenience and simplicity at one time competed and in some ways was even ahead Windows, however applications under QNX Little was written, which determined her future fate. Today QNX used mainly on specialized devices.

Red Hat 8.0 with GNOME 2.06 interface

Systems Linux, especially the early ones, were usually perceived as aimed at computer geeks, but it cannot be said that the developers Unix -like systems have done nothing to make their products as convenient as Windows. An example of this would be Red Hat 8.0- based on Linux Fedora OC with shell GNOME 2.06, by the way, was originally developed specifically for Red Hat and only then spread to other distributions Linux.

Red Hat 8.0 has a simple and clean desktop with the ability to place icons and other objects on it, Windows-like taskbar, windows, the controls of which were not located on the left, as is typical for many Linux-systems, and in the upper right corner, there is in Red Hat 8.0 even its own button and menu Start. The menus themselves are organized according to the cascade principle, which in terms of design makes this system even more similar to Windows.

Instead of an afterword

For more than half a century of its existence computer have come a long way, developing into complex and powerful systems that have found application in almost all modern industries. Comparing the first electronic computers with modern supercomputers is like comparing hot air balloon With spaceship. But what seems even more surprising is that their interfaces have not undergone fundamental changes, except for the transition to graphical shells themselves.

If you look closely at the interfaces of modern operating systems, you will notice obvious similarities with the graphical shells of the founders of all GUI And . What is this, a lack of imagination among designers or some kind of necessity dictated by the physiology of users? More likely the second than the first. Can this be considered as some kind of disadvantage? Of course not. Yes, the first graphical interfaces were primitive, but at the same time they also had that captivating simplicity that shells overloaded with visual effects sometimes lack modern programs and operating systems.

USER INTERACTION WITH THE OS

One of the three most important functions of an OS is its user interface. It is thanks to him that it is possible to run programs, control their execution and maintain file maintenance. These same tools for interacting with the operating system include many other tools and functions.

To date, two fundamentally different interface systems (translated as user interaction) have emerged. The first system is called command interface or command line interface. It allows the user to control the launch and execution of programs by specifying control texts from the text console, i.e. teams. Such a system developed in the early 70s of the 20th century and was most fully developed within the operating room. Unix systems. Note that control using special texts is very close in features to conventional programming in languages high level, and therefore the command interface is easily mastered by programmers, for non-professional users this approach can be as difficult as learning to program.

The second of the interface systems mentioned is graphical. It developed in the developments of PARC (Palo Alto Research Center of Xerox) in the late 70s of the 20th century, but was first widely used in operating systems Apple(MacOS) in the mid-80s, and then in operating shells, and later in operating systems from Microsoft. It is well known to the broad masses of non-professional users from the graphical shells of MS Windows 3.1, Windows 9x, Windows NT and their later modifications.

Control your computer using GUI is to the command line interface what watching comics (picture stories) is to reading works of fiction. There is no doubt that the first two options are easier for an inattentive or illiterate person, as well as for a person who is not used to bothering himself. At the same time, the number of users of both comics and graphical interfaces is an order of magnitude, if not orders of magnitude, greater than the users of strict texts.

Control using a graphical interface is psychologically much simpler and requires significantly less volitional effort, attention and memorized information. In practically a graphical interface, the necessary information is almost always present directly on the screen, where you are prompted to make one of the possible choices. But at the same time, complex configuration requires many dialog boxes, and in many cases the overall picture of the configuration turns out to be difficult to see. In practice, this approach is capable of solving only a small number of typical configuration problems, but has neither depth nor versatility. In ideological terms, the graphical interface is very close to the programming language Cobol, so beloved by Americans, which is designed to solve economic problems and allows you to write algorithms not using specialized and rather abstract operators, but using almost ordinary phrases of the English language. In particular, arithmetic operations in COBOL are not written mathematical symbols, and in English words add, subtract, multiply. A layman finds this style very comforting, but a professional is annoyed by the lack of compactness and clarity in information control structures.

Despite the widespread use of graphical interfaces in operating systems such as Windows, internal communication between the components of the operating system itself inevitably has the nature of control texts, in particular, machine commands and text calls of system functions. The fundamental complexity of setting an analogue of the impact on the graphical interface inside the program forces the command line interface to remain in the background, not visible to non-professional users. Therefore, almost all the attention in this chapter will be focused on the command line interface, and we will not consider the capabilities of the graphical interface, referring for its study to many guides on the superficial management of specific operating systems.

An interface is an intermediary that transforms computer control into a user-friendly form.

Before getting acquainted with the interface elements, let's look at the controls in Windows. It is generally accepted that the input devices for information in a PC are the keyboard and mouse. This is not entirely correct, since these elements are used not only for input, but also for controlling elements of the Windows OS.

The mouse is the main control element of the Windows OS. It contains, as a rule, two control buttons: left and right, and a scroll wheel. The left key is multifunctional; it can be used to perform a number of operations: launching programs, selecting objects, “dragging” objects, etc. The right key is used to launch the Context Menu. The scroll wheel is used to move around within a document. In laptops, a “touchpad” is provided as a replacement for a mouse - a special touch-sensitive pad.

The keyboard is mainly used for entering text in documents, however, it can also act as a control element using control and so-called “hot” keys. The keys are intended for their use Ctrl And Alt.

The Windows OS interface consists of the desktop, taskbar, icon system or shortcuts, and user menu.

Rice. 2.2 Worker Windows table 7.

The desktop is the image on the monitor screen that appears after loading the PC, on which the main control elements are located. The main ones are icons. Using icons, various objects are displayed: launching programs, documents, disks, folders, graphic and video files, etc. Moreover, objects can be presented both in the form of the objects themselves and in the form of links to objects. In the second case, the icons are called shortcuts, and have a small arrow pointer in the lower left corner. The number and location of icons on the desktop is individual for each user. Working with icons is controlled by the mouse.

The taskbar is located at the bottom of the desktop and consists of the “notification area” on the right side, the “taskbar” on the left side, and the Start button on the far left.

The “notification area” contains various information necessary for current work on the computer. The “taskbar” displays running applications. The Start button contains the user menu.

These elements are manipulated using the mouse pointer.

For example, to view documents opened in this moment in Word, you need to place your mouse pointer on the Word icon on the taskbar. All open documents will appear on the screen as separate windows.

Rice. 2.3. Taskbar with open documents.

The user menu, launched by left-clicking on the Start icon, is the main component of the Windows OS. It contains the basic elements of working with a computer.

Figure 2.4. User's menu.

The menu consists of two columns.

On the left are icons for the most frequently used programs. The arrows to the right of programs show a list of the most recently opened files in this program. The inscription “All programs” is a list of all programs installed on the computer. At the very bottom there is a search line, which keyword Easily find any file or folder on your computer.

· “Computer” opens the file manager;

· "Control Panel" - Windows settings;

· “Default programs” associate the document type with the corresponding application program;

· “Help and Support” - a detailed electronic textbook on Windows;

· “Shutdown” is used when turning off the computer.

The presentation of information in Windows is built in the form of windows.

Rice. 2.5. Computer folder window.

The window consists of the following elements:

· window title, which indicates open program;

· window control buttons (collapse, expand to full screen, close);

· user's menu;

· toolbar;

· information part.

The window can be positioned arbitrarily on the desktop, and the window size can be changed. When working with multiple programs, you can have multiple windows open at the same time. This mode of operation is called multi-window. The transition from one window to another is carried out using the mouse pointer.

The easiest way to configure the interface is by calling context menu by right-clicking on a free area of ​​the desktop. The “personalization” command opens a window with various elements for customizing the Windows interface.

Rice. 2.6. Interface settings.

Windows Appearance includes the following elements: desktop background, cursor, color scheme, system sounds, etc. Any of these elements can be changed separately, but the easiest way is to select a set of settings in the form Topics. Microsoft offers a fairly wide selection of themes, including high-contrast designs for people with low vision.

One of the main parameters of the image on the monitor screen is permission screen. It is set in the form of indicating the number of horizontal and vertical dots in the settings of the “Screen” menu item. Default upon installation Windows systems The most rational image scheme on the screen is installed on the computer. Despite the possibility of independently adjusting the image, it is recommended to change them only when replacing the monitor, since the monitor parameters affect the image quality.

Another design element is gadgets– mini-applications. They are installed using the “gadgets” item in the context menu.

Rice. 2.7. Gadgets.

The gadget can be placed anywhere on the desktop and installed on top of all windows. In this case, it is useful to make the gadget translucent so that it does not interfere with work. If you wish, you can expand your collection of gadgets on the Internet.

OS functions, user interface.

operating system, OS (English) operating system) - basic complex computer programs, providing control of computer hardware, working with files, input and output of data, as well as execution of application programs and utilities.

operating system is a set of programs, rules and special data that jointly manage computer resources and processes that use these resources in their work.

Operating system (OS)

1. this is a set of programs that ensure the joint functioning of all computer devices and provide access to its resources

*.sys - system files

*.bak - safety file

Regardless of versions, DOS is ensured by the following 3 components:

1. basic input/output system (BIOS) (or RIOS). The program recorded in ROM is supplied by computer manufacturers and performs the function of ensuring normal functioning: checking completeness, testing various devices PC, DOS boot initialization and a number of other functions. This program is not a file and is not actually included with QOS;

2. The DOS kernel contains in the form hidden files: bootstrap block located in the first sector system disk(read by the BIOS) and ensures that the operating system is loaded into the machine’s memory - IO. SYS (or IBM), the so-called software-assisted basic input/output system peripheral devices(BIOS extension and patch), as well as an MS DOS file. SYS (IBM), containing programs for managing files, memory, running programs, etc. This file is sometimes called the interrupt control module because software (DOS functions) are accessed from the user program using software interrupts;

3. a file, or command processor (interpreter), whose functions include receiving, checking commands entered by the user from the keyboard, and executing them. There are 3 categories of DOS commands - resident or internal, permanently located in the operating system, semi-resident, which can (as necessary) be “overwritten” by application programs, and external, called as needed from external memory.

There are two types of MS DOS commands:

Internal commands are executed by the command processor (for example, dir, copy). External commands- programs supplied with the OS in the form separate files. They are located on the disk and perform maintenance actions (for example, formatting the disk, clearing the screen, checking the disk).

Commands consist of a command name and optionally parameters, separated by spaces. Optional command elements will be marked with parentheses.

Working with files

Creation text files copy con filename. After entering this command, you will need to enter the lines of the file one by one. At the end of each line you need to click the Enter key. And after entering the last one, press Ctrl and Z at the same time, and then Enter.

Deleting files del (path) filename. The path is written only when the file to be deleted is in a different directory.

Renaming files ren (path)filename1 filename2. File_name1 is the name of the file you want to rename, file_name2 is the new file name that will be assigned to it after executing the command.

Copying files copy filename (path)filename1.

Copy games. txt games copy the games. txt to the GAMES subdirectory of the current disk.

Working with catalogs

Command to change current disk A:- go to drive A.

Browse directory dir (path) (filename) (/p) (/w).

If the path and file name are not entered, information about the contents of the directory (file names, their size and the date of last modification) will be displayed on the screen.

The /p parameter specifies display of information in screen-by-screen mode, with a delay until the user clicks a key. This is convenient for large directories, /w - sets the output of information only about the names of files in the directory, five names per line.

Changing the current directory CD path.

Creating a directory md path.

Removing a directory rd path.

Examples:
dir- display the table of contents of the current directory;
dir*.exe- display information about all files with the extension. exe from the current directory;
dir a:- display the table of contents of the root directory of drive a:.
cd games- go to the GAMES directory of the current disk;
cd..- go to the previous directory;
CD- go to the root directory of the current disk.
rd games - deleting the GAMES subdirectory in the current directory;
ATTENTION! YOU CAN ONLY DELETE AN EMPTY DIRECTORY!

Command line

This is the line you will see on the screen after loading MS DOS. It is also called a DOS prompt and looks like this:

C:\> ,

here C: is the drive name; > is a prompt symbol, after which the cursor blinks, indicating the place where the command should be entered.

Other teams.
Date- display information about the date with the ability to customize.
Time- display of time information with the ability to configure.
Verify on- enable disk write check mode.
Verify of- turn off the disk write check mode.
Verify- display information about whether the disk write check mode is enabled.
Path- determines the search order for the most frequently launched programs.
Ver- shows the operating system version.
Cls- cleans the screen.
Label- displays information about the disc label with the ability to change it.

Structure and general principles building a program in Turbo Pascal. Alphabet. Constants. Variables.

General structure of programs in Pascal language

Pascal programs have the following general form:

Program Program name

Descriptions section

Operators section

The words PROGRAM, BEGIN and END highlight 2 parts of the program: the description section and the statement section. This structure is required. Any object used in the program must be included in the descriptions section.

A program written according to the rules of the standard Pascal language must have the following structure in its complete version:

Program program name;

Uses List of modules used

Label List of labels from the main block of the program

Const Definition of program constants

Type Description of types

Var Description of Variables

Procedure Procedure text

Function Function text

Main block of the program

(operators section)

Syntax and semantics

The description of each language element is given by its syntax and semantics. Syntactic definitions establish rules for constructing language elements. Semantics defines the meaning and rules of use of those language elements for which syntactic definitions have been given.

Language alphabet

An alphabet is a set of symbols allowed in a language. The Turbo Pascal alphabet includes the following set of basic characters:

lowercase and uppercase Latin letters: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z; a b c d e f g h i j k l m n o p q r s t u v w x y z; space underscore: _ Arabic numerals: 8 9 operation signs: + - * / =<> < > <= >= := @ delimiters: . , " () ( ) (* *) .. : ; specifiers: ^ # $ service (reserved) words:

ABSOLUTE EXPORTS LIBRARY SET

ASSEMBLER EXTERNAL MOD SHL

· AND FAR NAME SHR

ARRAY FILE NIL STRING

ASM FOR NEAR THEN

ASSEMBLER FORWARD NOT TO

BEGIN FUNCTION OBJECT TYPE

CASE GOTO OF UNIT

CONST IF OR UNTIL

CONSTRUCTOR IMPLEMENTATION PACKED USES

DESTRUCTOR IN PRIVATE VAR

DIV INDEX PROCEDURE VIRTUAL

DO INHERITED PROGRAM WHILE

DOWNTO INLINE PUBLIC WITH

ELSE INTERFACE RECORD XOR

END INTERRUPT REPEAT

EXPORT LABEL RESIDENT

Elementary structures

The elementary constructs of Pascal include names, numbers, and strings.

Names (identifiers) call the elements of the language - constants, labels, types, variables, procedures, functions, modules, objects.

An identifier in Turbo Pascal may include:

3. underscore character.

Lowercase and capital letters Not. A digit cannot appear first in an identifier, and an underscore can appear in any position (for example, name1 and name2item are valid identifiers, but 5name is not; _name, name_, name_item are also valid names). The identifier can be any length, but only the first 63 characters are significant. It is not allowed to use function words as names.

To separate identifiers, numbers, reserved words separators are used. You can use them as:

1. space and tab;

2. line feed;

3. comment.

In any place in the program where one separator can be placed, they can be placed in any number and in any combination, which allows you to visualize the structure of the program.

There are several fundamental concepts in the field of information technology. One of them is the “interface”. Note that it can be interpreted from different points of view. The previous chapter described the concept of "Interface" system calls". If you search for such a term in the Yandex Dictionaries, you will receive more than a dozen definitions of the term, most of which are given in combination with other terms, for example: “Data transfer interface”, “Program interface”, “Application interface”. In the dictionary “Natural sciences” on GLOSSARY .RU gives the following definition of a fundamental concept.

An interface in a broad sense is a boundary between interacting independent objects defined by standards. The interface specifies the parameters, procedures and characteristics of the interaction of objects.

In the "Publishing Dictionary-Reference Book" there is such a definition of the basic term "interface". This:

1. System of connections and interaction of computer devices.
2. Means of user interaction with the computer operating system, or user program. There are graphical user interfaces (interaction with the computer is organized using icons, menus, dialog boxes, etc.) and intelligent interface (means of user interaction with the computer in the user’s natural language).

As you can see, here this term has two meanings. But we will briefly dwell on the second one - the “user interface”. On the source GLOSSARY .RU already mentioned by us, it is defined as follows: “The user interface is the elements and components of the program that are capable of influencing the user’s interaction with software, including:

• means of displaying information, displayed information, formats and codes;
• command modes, user interface language;
• data input devices and technologies;
• dialogues, interactions and transactions between the user and the computer;
• user feedback;
• decision support in a specific subject area;
• the procedure for using the program and its documentation."

As the computer technology methods and means of user interaction with the operating system have changed. Widespread digital computers led to a mode of communication between a person and a computer in a special language. At first, during the period of batch processing of tasks, this was realized using special storage media (for example, punched cards on which tasks for the computer were written). But later, with the widespread use of terminals and keyboards, the main thing became command mode user work, in which interaction was based on a system of built-in commands. In the free encyclopedia "Wikipedia" it is defined as follows.

Command line interface (CLI) is a type of text interface (CUI) between a person and a computer, in which instructions to the computer are given mainly by entering text strings (commands) from the keyboard; in UNIX systems it is possible to use a mouse. Also known as "console".

Here is an approximate fragment of the screen that appears in command line mode (Fig. 4.1).

Rice. 4.1.

A prompt () appears on the left side of the line, after which you can type a command, the results of which are displayed below. Here is an example of executing the date command in Linux system(Fig. 4.2).

Microsoft's first operating systems for personal computers IBM PCs (called MS DOS) also supported command mode, similar to other systems. The line in which the commands were typed was similar to those given above. Today, the command mode of operating systems is provided by the cmd.exe (for 32-bit mode) or command emulators. com (for 16-bit mode). In graphical mode of the UNIX/Linux family command line emulated by the Terminal program (xterm).

Note that for computers with the MS DOS operating system, the legendary Norton Commander program has become a successful addition to the implementation of such a user interface. It minimized typing activities in command line, allowing you to operate, first of all, by selecting the appropriate command from the menu. This program also makes extensive use of the computer's function keys. Wikipedia describes this system as follows:

"Norton Commander (NC) is a popular file manager for DOS, originally developed by American programmer John Socha (some additional components were written in whole or in part by others: Linda Dudinyak - Commander Mail, viewers; Peter Bradeen - Commander Mail; Keith Ermel, Brian Yoder - viewers). The program was released by Peter Norton Computing (headed by Peter Norton), which was later acquired by Symantec Corporation."

Here is an example screenshot of this file manager(Fig. 4.3).

The popularity of the program was so great that numerous clones appeared that more or less accurately copied Norton's