A practical introduction to Pascal programming language - GIARA

More documents

Recommendations

Info

Chapter 1Basic read/write operations1.1 Contents of this chapterThis chapter covers the instructions used to gather data from the user, as well as displayinon-screen the information generated by a program. Its contents are:1.a Writing in the command line.1.b Reading from the keyboard.1.c Basic assignment operations.1.d Usage of simple functions provided by the programming framework.1.2 Brief reviewThis section cover the most basic read/write operations. There are two operations we can use towrite text in the command line: write(t) - Writes the text t in the command line (more on the composition of t later). writeln(t) - Does the same as write(t), but jumps the line right after writing the text.That is, places the prompt at the beginning of the line following.The composition of the text to be displayed by write/writeln can be performed in differentways. These are the options:• Simple static text between simple quotations.writeln(’computer’).Some examples are write(’hello’) or• Concatenation of static texts. To do so, we only have to include as many pieces oftext as necessary, all of them separated by the comma symbol. Some examples arewrite(’hel’,’lo’) or writeln(’this ’,’is ’,’my computer’). Note that, for example,write(’hel’,’lo’) produces the same message on-screen than write(’hello’).• Concatenation of static text and non-static values. In this case we can combine the fixedtext with contents derived from the contents of the variables. To concatenate fixed textwith non-fixed content, we also use the comma symbol. Some examples are write(’211
A Practical Introduction to Pascal Programming LanguageFunction Usage Input OutputAbsolute value abs(x) Int Same as inputSquared value sqr(x) Int./Real Same as inputSquared root sqrt(x) Int./Real Same as inputTrigonometric Sine sin(x) Int./Real RealTrigonometric Cosine cos(x) Int./Real RealNatural logarithm ln(x) Int./Real Reale-power exp(x) Int./Real RealTruncated value trunc(x) Real Int.Rounded value round(x) Real Int.Fractionary part frac(x) Real RealReal part int(x) Real RealTable 1.1: Some of the most important functions in Pascal, together with the type of inputs theydemand and the outputs they produce.multiplied by 2 is ’,2*2) or write(’The value of a is ’,a), where a can be anykind of variable. Note that, regardless of the type of variable, the program will automaticallyconvert it to text for its display in the write/writeln operation.Regarding the reading-from-keyboard operations, here are two functions we can make useof: read(a) - Waits for the user to input information on the command line and stores it in thevariable a. readln(a) - Waits for the user to input information and press enter on the command line.Then, it stores all the information the user typed in the variable a.After the execution of any of such functions, the value of the variable put into parenthesis isthe one the user input. In case the contents input by the user cannot be appropriately convertedto the type of the variable, an error is raised, and the execution of the program is aborted.Apart from the read/write operations, Pascal offers a wide variety of functions for easing thecomputations. A selection of such functions can be found in Table 1.1, where the name of eachfunction is listed together with the type of arguments it admits and the type of the information itproduces. Note that this functions could be combined in any possible way, exactly as the usualmathematical operators.1.3 Exercises1.3.1 Basic input and outputExercise 1.1. Write a program that reads an integer from the keyboard and shows it to the user.□For doing this exercise we only need to declare one variable, which is read and displayedusing two different operations. Note that, by using readln, we save into int all the digits typedby the user before an enter, not only the first one.12
Page 4: A Practical Introduction to Pascal
Page 8: ContentsIntroduction to this book 9
Page 11: Guidelines and structureThis book i
Page 15 and 16: A Practical Introduction to Pascal
Page 63 and 64:
A Practical Introduction to Pascal
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91:
show all

A practical introduction to Pascal programming language - GIARA

Create successful ePaper yourself

Delete template?

Save as template?