What is measured in pascals? units of measurement
On the vastness of the World Wide Web you can find a lot of programs in the Pascal language, but it is much more difficult to understand on what principle they work and how they are structured. Let's learn the basics of programming together!
Algorithmic language: basic concepts
In colloquial speech we use basic units: symbols and whole sentences. The algorithmic language also has a similar structure, only its components are called differently. We are talking about elementary constructions, expressions and operators. All these units form a hierarchical structure, since each subsequent element is formed from the previous one.
The symbols of an algorithmic language are the indivisible atoms used to write code.
Elementary structures are minimal units that have their own meaning.
Classic language expressions are formed from the two above-mentioned units and set the rules for finding the required meaning.
The operator is responsible for describing a certain transformation, which is mandatory for the correct execution of the program. There can be several of them, if necessary - the program must perform a complex operation. In such situations, they are combined into a block or a compound statement.
Pascal language
There are a large number of "Pascal" (there are separate manuals for beginners) is one of them. Its alphabet consists of numbers, letters and special characters. Here is their list:
- 26 Latin capitals and ;
- underscore;
- ten digits;
- limiters;
- operation signs;
- specifiers;
- system-reserved (service) words.
In addition to the elements listed above, the basic set includes “space,” which cannot be used within the construction of reserved expressions and double characters.
Elementary language structures
"Pascal" for beginners includes strings, numbers and names.
Numbers used in the code of the programming language in question are usually written in the decimal system. They can be either real or integer, which are usually mentioned without a decimal point. If the number is positive, then its sign can be omitted.
Pascal is an algorithmic programming language in which strings are a sequence of characters enclosed in apostrophes. If you must use the apostrophe itself, it is worth mentioning this symbol twice.
A name is a sequence that begins with a letter and may contain numbers. Identifiers are commonly used to refer to labels, types, constants, functions, procedures, variables, objects, and even modules. When forming identifiers, you can use the underscore character. The name can have a lot of characters, but the compiler will only read the first 63 characters. “Pascal,” the description of which may seem so complicated, is not so scary, so don’t rush to get scared and close the browser page!
It is prohibited to use standard names of constants, procedures, types, files, functions, as well as service expressions as language identifiers.
Spaces will help improve the clarity of the code, but it is worth remembering that they cannot separate names and numbers in the middle.
Algorithmic language syntax
Each line must end with a semicolon in a program written in the language we are considering (Pascal). Computer science teaches this to schoolchildren and students, and you can understand these rules yourself!
The semicolon (;) is a conditional signal that indicates the end of the current line and the need to move to a new one. But the exception may be service commands: const, var, begin and others.
The end statement closes the program, so it must be followed by a period. Sometimes the code may contain several attachments, then the beginning and end of the block will be separated by a semicolon.
To assign a specific value to a variable, you must place a colon before the equal sign. For example, you want to set n=13, but in the code it will look like n:=13.
If you learn these rules, you can quickly learn how to write program code without syntax errors.
Classic Pascal operators
You can program repeating code fragments of a future application and perform any actions with it using various methods. But the Pascal language uses various operators for this. We will not be able to consider all of them, so we will deal with only a few.
For example, using the selection operator, you can select one of the alternative paths for the program. The parameter in this case is an expression of ordinal type. But there is one caveat: this select key cannot be of type string or real.
There are also assignment operators, conditional operators, compound operators, and empty operators, as well as a host of other useful attachments. Knowing just a few of them allows you to write code with excellent functionality. Operators should not be overused, because their large number makes the program difficult to debug with a compiler, confusing and very difficult for outsiders to understand.
Assignment operator
This expression takes the form of a colon and an equal sign. It is used to assign a specific value to a specific variable. It is important to remember that the type of an expression and a variable must be the same unless they are an integer and a real type, respectively. Only in such a situation will direct transformation take place.
Compound Operators
Pascal is a programming language that uses sequences of arbitrary program statements enclosed in special parentheses. We are talking about compound structures limited by the words begin and end. It is an important tool in an algorithmic language that makes it possible to write code using a structured methodology.
The Pascal language operators that are part of a compound construction can be completely different, because there are no restrictions. The depth of nesting can also be different.
Conditional operator of a programming language
This component provides the ability to check a given condition during the program and perform an action depending on the results of its passage. Thus, a conditional command is one of the means of forming branches in the process of performing calculations.
Structurally it looks like this:
IF<условие>THEN<оператор1>ELSE<оператор2>.
In this expression, else, then and if are reserved words, the condition is a logical expression with arbitrary content, and the operators are any commands of the programming language used.
Program code structure
The header, statement and description sections are the key components of an application written in a language such as Pascal. Computer science allows you to fully explore these elements and learn how to use them correctly.
The header usually contains the name of the code. For example, Program MyFirst.
The descriptions section may include connected libraries, modules, labels, constants, types, variables, and a chapter describing functions and procedures.
The module description section contains the names of the included libraries and begins with the reserved word uses. It should come first among all other descriptions. Module names must be separated by commas.
You can put a label on any program code statement, the name of which should be mentioned in the corresponding section of the description.
Premature description of constants allows you to write their names later in the code instead of numeric or alphabetic values.
In the section describing the variables used, you should indicate all the types that will be used: "var c,a,r: integer; k,l, m: char; h1,h2: boolean;".
Do not forget that Pascal is a programming language that requires a mandatory preliminary description of all the components involved in the program.
The code text must end with a period.
Example programs
"Pascal" is an elementary language, and after studying the information described above, you can proceed directly to writing code.
Let's make the application display the phrase “It is my first program!”
The Pascal sample programs are very important to understand, so try it now.
Begin
Writeln(It is my first program!");
End.
It's that simple!
Look at more complex code that can be used to find roots. Pay attention to the principle of forming computational expressions.
We hope you found it useful.
Pascal (SI unit)- Pascal (symbol: Pa, Pa) a unit of pressure (mechanical stress) in SI. Pascal is equal to the pressure (mechanical stress) caused by a force equal to one newton, uniformly distributed over a surface normal to it... ... Wikipedia
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Pascal (Pa, Pa)
Pascal (Pa, Pa) is a unit of measurement of pressure in the International System of Units (SI system). The unit is named after the French physicist and mathematician Blaise Pascal.
Pascal is equal to the pressure caused by a force equal to one newton (N) uniformly distributed over a surface of one square meter normal to it:
1 pascal (Pa) ≡ 1 N/m²
Multiples are formed using standard SI prefixes:
1 MPa (1 megapascal) = 1000 kPa (1000 kilopascals)
Atmosphere (physical, technical)
Atmosphere is an off-system unit of pressure measurement, approximately equal to atmospheric pressure on the Earth's surface at the level of the World Ocean.
There are two approximately equal units with the same name:
- Physical, normal or standard atmosphere (atm, atm) - exactly equal to 101,325 Pa or 760 millimeters of mercury.
Technical atmosphere (at, at, kgf/cm²)- equal to the pressure produced by a force of 1 kgf, directed perpendicularly and uniformly distributed over a flat surface with an area of 1 cm² (98,066.5 Pa).
1 technical atmosphere = 1 kgf/cm² (“kilogram-force per square centimeter”). // 1 kgf = 9.80665 newtons (exact) ≈ 10 N; 1 N ≈ 0.10197162 kgf ≈ 0.1 kgf
In English, kilogram-force is denoted as kgf (kilogram-force) or kp (kilopond) - kilopond, from the Latin pondus, meaning weight.
Notice the difference: not pound (in English “pound”), but pondus.
In practice, they approximately take: 1 MPa = 10 atmospheres, 1 atmosphere = 0.1 MPa.
Bar
A bar (from the Greek βάρος - heaviness) is a non-systemic unit of pressure measurement, approximately equal to one atmosphere. One bar is equal to 105 N/m² (or 0.1 MPa).
Relationships between units of pressure
1 MPa = 10 bar = 10.19716 kgf/cm² = 145.0377 PSI = 9.869233 (physical atm.) = 7500.7 mm Hg.
1 bar = 0.1 MPa = 1.019716 kgf/cm² = 14.50377 PSI = 0.986923 (physical atm.) = 750.07 mm Hg.
1 atm (technical atmosphere) = 1 kgf/cm² (1 kp/cm², 1 kilopond/cm²) = 0.0980665 MPa = 0.98066 bar = 14.223
1 atm (physical atmosphere) = 760 mm Hg = 0.101325 MPa = 1.01325 bar = 1.0333 kgf/cm²
1 mm Hg = 133.32 Pa = 13.5951 mm water column
Volumes of liquids and gases / Volume
1 gl (US) = 3.785 l
1 gl (Imperial) = 4.546 l
1 cu ft = 28.32 l = 0.0283 cubic meters
1 cu in = 16.387 cc
Flow speed
1 l/s = 60 l/min = 3.6 cubic meters/hour = 2.119 cfm
1 l/min = 0.0167 l/s = 0.06 cubic meters/hour = 0.0353 cfm
1 cubic m/hour = 16.667 l/min = 0.2777 l/s = 0.5885 cfm
1 cfm (cubic feet per minute) = 0.47195 l/s = 28.31685 l/min = 1.699011 cubic meters/hour
Throughput / Valve flow characteristics
Flow coefficient (factor) Kv
Flow Factor - Kv
The main parameter of the shut-off and control body is the flow coefficient Kv. The flow coefficient Kv shows the volume of water in cubic meters per hour (cbm/h) at a temperature of 5-30ºC passing through the valve with a pressure loss of 1 bar.
Flow coefficient Cv
Flow Coefficient - Cv
In countries with an inch measurement system, the Cv coefficient is used. It shows how much water in gallons/minute (gpm) at 60ºF flows through a fixture when there is a 1 psi pressure drop across the fixture.
Kinematic viscosity / Viscosity
1 ft = 12 in = 0.3048 m
1 in = 0.0833 ft = 0.0254 m = 25.4 mm
1 m = 3.28083 ft = 39.3699 in
Units of force
1 N = 0.102 kgf = 0.2248 lbf
1 lbf = 0.454 kgf = 4.448 N
1 kgf = 9.80665 N (exactly) ≈ 10 N; 1 N ≈ 0.10197162 kgf ≈ 0.1 kgf
In English, kilogram-force is expressed as kgf (kilogram-force) or kp (kilopond) - kilopond, from the Latin pondus, meaning weight. Please note: not pound (in English “pound”), but pondus.
Units of mass
1 lb = 16 oz = 453.59 g
Moment of force (torque)/Torque
1 kgf. m = 9.81 N. m = 7.233 lbf * ft
Power Units / Power
Some values:
Watt (W, W, 1 W = 1 J/s), horsepower (hp - Russian, hp or HP - English, CV - French, PS - German)
Unit ratio:
In Russia and some other countries 1 hp. (1 PS, 1 CV) = 75 kgf* m/s = 735.4988 W
In the USA, UK and other countries 1 hp = 550 ft*lb/s = 745.6999 W
Temperature
Fahrenheit temperature:
[°F] = [°C] × 9⁄5 + 32
[°F] = [K] × 9⁄5 − 459.67
Temperature in Celsius:
[°C] = [K] − 273.15
[°C] = ([°F] − 32) × 5⁄9
Kelvin temperature:
[K] = [°C] + 273.15
[K] = ([°F] + 459.67) × 5⁄9
What is Pascal? Quite a lot of people ask this question. These are mainly people who use a computer at a basic level. Pascal is one of the most famous programming languages. It is studied, as a rule, in high school or in the first years of university. It is considered the basis for many other programming languages.
Story
We found out what Pascal is. Let us now move directly to the history of its appearance and development. The creator of the language is Niklaus Wirth. It was developed between 1968 and 1969. The idea for Pascal came to him after participating in a special committee on language development. What is Pascal is of interest to many novice programmers. The language received this name in honor of the famous French scientist who is especially famous for the creation of a mechanical machine that summed two numbers.
The first publications about what Pascal is appeared in 1970. They talked about the main goals of creating this language, such as efficiency, which would promote excellent programming and data structuring skills.
Implementation of the language
- UCSD Pascal. This system was created in 1978. It added a compiler port that made the code portable, it was also now possible to edit the source system, and so on. Subsequently, UCSD became the basis for many subsequent implementations of the Pascal language.
- Object Pascal. Programming in Pascal has always attracted many beginners. In 1986, Apple created an object extension for the language. The development team consulted with Pascal's "father".
- Turbo Pascal. The first version of the integrated development environment appeared in 1983. Borland became the company that began developing this implementation. However, it is worth noting that Turbo Pascal borrowed a lot from Odject Pascal, and in general these implementations were similar. Programming in Pascal also interested Microsoft. Almost at the same time, they released their own version of an object language based on Pascal. It failed to gain mass distribution and was soon forgotten. Subsequently, Borland's implementation was called Object Pascal.
- Object Pascal today. The most important step in the history of the Pascal language is the release of free implementations. They included the best of many other dialects. They have excellent compatibility with most operating systems.
Peculiarities
To get acquainted with the Pascal language, you need to start with its features. The main one is the strictest typing and the presence of Pascal - the first of this kind of languages. According to the developer, the language should contribute to disciplined programming, since it eliminates various syntax errors as much as possible, and also has an intuitive interface. What is Pascal and what are its main features are the main questions that interest novice programmers. The language is quite simple even for a beginner.
However, initially the language had a number of shortcomings. The main ones are: the inability to work with a short I/O library, lack of tools to run functions created in other languages, and so on. What Pascal is, the language of which is quite simple, was learned by many specialists in the early 80s. However, not everyone liked it. Some experts even wrote articles in which they described in detail each disadvantage of the language.
Disadvantages and their correction
Like many other programming languages, Pascal boasts not only advantages, but also serious disadvantages. It should be said that developers are gradually struggling with the disadvantages, but they do not always succeed.
No matter how it sounds, it’s not uncommon that language shortcomings helped programmers in their learning. In addition, Pascal in the 80s was a huge step forward in comparison with Fortran, which was studied by beginners at that time. Moreover, Fortran had even more problems. In a very short period of time, Pascal managed to become the main language of instruction in many schools and universities. Numerous programs began to be developed on its basis.
Structure
You can write a lot about the Pascal language, but you should go directly to the programming process. Every application in Pascal begins with a keyword (Program). Immediately after it, indicate the name of the program, and then put ";". Sometimes this is not required. After the name, you can specify a list of external files that will act as parameters. After that comes the most important thing in the program - her body. It consists of sections describing constants, types, variables, procedures and functions. After them comes a block of operators - the entry point. The statement block is located between the begin and end keywords. Each statement is separated by a semicolon. To end the program, a period is used, which is placed after the body.
Application of modules
To use a module, a declaration about it must be present in the program code. You can make such a declaration using a connection statement, which is the USES keyword. After it are indicated the names of the modules that need to be connected. The instructions are placed immediately after the title or in the interface sections.
Some language implementations do not support modules, especially older versions. They can be divided into two types: software and auxiliary. The first one is present in the program, starting with the keyword program. The second contains variables, constants, types, etc., and can be used in other modules.
Punctuation
Pascal's syntax requires strict execution.
- Semicolon. Placed at the end of the title, after the description of the variables. It is used to separate operators. It may not be used before the end keyword.
- Comma. Used as a separator in various lists.
- Dot. Placed at the end of the program body (after the word end).
This strict syntax is necessary because the computer is considered the executor of the application. If an incorrect character is used, an error is displayed. If a semicolon acts as a statement separator, then all text located between one semicolon and the next is considered a statement. If this sign is not placed between operators, the program will perceive them as one and also generate an error.
The Pascal language allows you to insert comments. They serve as an explanation of the program code. You can use Russian. Comments have no effect on the operation of the program.
In Pascal you can write in both lowercase and uppercase letters. The choice is up to the programmer.
Criticism
As already mentioned, Pascal became especially popular in the 1980-1990s, but there were critics who considered the language frivolous. In their opinion, it is only suitable for training. A particularly notable criticism was presented in the article "Why Pascal is not my favorite programming language." It was written by Brian Kernighan, one of the developers of the C language. It was after the article that Pascal began to seriously change for the better.
Despite all its shortcomings, the thing that weighs most heavily on Pascal is the frivolous attitude of many programmers.
You are in the Pascal programming materials section. Before we start programming, we need to clarify some concepts that we will need in the beginning. After all, you can’t just program like that. We cannot write the program in words - the computer does not understand anything other than zeros and ones. For this purpose, special symbolism was created in Pascal - the Pascal language, a set of reserved words that cannot be used anywhere else in your programs except for their intended purpose. Let's list the basic concepts that we will need at the beginning:
✎ 1) program – in English “program”, written at the very beginning of the code, followed by the name of the program in Latin and a semicolon. For example: program Summa; − a program called Summa. But this part of the code, called the program header, does not need to be written - it is present only for clarity and shows what problem this program solves. Here we used the word “code” - this is the name of the text entry of the program.
✎ 2) integer – in English means “integer” (or simply “integer”) and in Pascal is used to denote 32-bit (8 bytes) signed integers from the range [-2147483648, 2147483647] . We will look into what these large numbers mean later.✎ 3) real – from English “real”, “real”, “real”, “real”. In the Pascal language, this term denotes real numbers in the range [-1.8∙10 308, 1.8∙10 308]. These are very large numbers, but 15 - 16 significant digits are displayed. By the way, the integer and real data types in the PascalABC.Net programming environment are always automatically highlighted in blue.
✎ 4) const – analogue of English. "constant", meaning "constant", "constant". In Pascal, this is a quantity that cannot change. It is written like this:
This entry must be taken as it is written: the number N is 12, S is 5, “pi” is 3.14 (as in mathematics, only a dot is used instead of a comma in Pascal). In the last line we used a double slash (two forward slashes), followed by text - this is how comments are written in Pascal, and the program does not perceive them. Everything that begins with a double slash and until the end of the line is a comment, which is written to explain the program and is always highlighted in a different color (in PascalABC.Net it is green; Turbo Pascal does not use this type of comment). There is another type of comment - this (text enclosed in curly brackets, just like here, also highlighted in green). This type of comment can be valid for several lines in a row - from the beginning of the bracket to its closing, and the compiler does not perceive everything that is in the middle of such a construction as code and simply skips it.
In reality the recording format const a little more complicated. According to the rules, we had to write:
|
After declaring each value, its type is indicated, and then a value is assigned. But the previous entry is also correct, since the Pascal compiler is configured so that it automatically determines the type of a constant. But this cannot be said about the next type of numbers - variables.
✎ 5) var – comes from English. “variable” (“variable” or “changeable”), which in Pascal means a value that can change its value during the program. It is written like this:
As can be seen from the entry, there is no “=” sign here - variables of the same type are recalculated (separated by commas) and only the type is indicated after the colon. The variables N, m (integer) and Q, r, t (real) in the program can change values within the limits of integer and real, respectively. One more note: the description of variables always comes after the description of constants (constants) - the const construction comes first, and then var.
✎ 6) begin – translated from English means “to begin” and Pascal means the beginning of the main program in which commands (operators) are written. After the word begin There is no semicolon.
✎ 7) end – in English. “end”, and in Pascal it means the same thing (end of the program). After the last word end there is always a period. We have emphasized the word “last” because the use of the construction begin–end perhaps in one more case: these are the so-called operator brackets, which are used to combine several operations under one operator. But more on that later. So the main program will look like this:
|
Here, the operators in the body of the program are different commands to the compiler.
✎ 8) write – in English means “to write”. This operator displays the text placed in it, which is why it is called the output operator. The text placed inside it is highlighted in blue and written like this:
Write( "this text is displayed on the screen");
A message inside parentheses and quotes will be shown in the console window (you can't just put it in parentheses without quotes). After executing this statement we will see on the screen:
this text is displayed on the screen
In this form, the write operator is used in the case when you need to show a hint, explanation, comment, etc. And if you also need to display a numerical value, say, S = 50 sq. m, then the format is used:
Write(, S);
As a result, we get the result on the screen:
The area is equal to: S = 50
And if you need to display units of measurement, you need to insert the text in quotes again after S:
Write( "The area is equal to: S = ", S, " sq.m" );
After executing the last output statement, we get the following output on the screen:
The size of the area is: S = 50 sq.m
✎ 9) writeln – the same as write, but after execution the cursor will be moved to the next line.
✎ 10) read – translated from English means “to read”, so read is called the read or data input operator. It is written as read(N), which means that the value N must be entered, where N is any number, or text, or other type of variable. For example, if we need to enter the age of a person who is 32 years old, we can write it like this:
In the first line of this code, the program displays the question “ What is your age?" and moves the cursor to the next line (ending ln); in the second line we print “Year =” (space at the beginning); Next we see the readln(Year) operator, which means it is necessary to enter the age Year (number 32); finally, we display the messages “My age”, “32” and “years. " one by one. You need to watch the spaces carefully. As a result of executing this code, we will receive the message:
What is your age?
Year = 32
My age is 32 years old
✎ 11) readln – the same as read, only with a new line. Indeed, in the above example, after introducing the number Year, we only write in the next line: “ My age is 32 years old».
That's all for now. On the next page we will write the first program, and in Pascal programming this will be our