1 / 10

The CONST definition

Learn about constant identifiers, string variables, integers, reals, and formatting output techniques in Pascal programming. Understand how to declare, assign values, and format data types for effective coding.

nicholasthompson
Download Presentation

The CONST definition

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The CONST definition • CONST Pi = 3.14159, City = ‘New York’; • Constant identifiers are used when you do not want the value of an identifier to change • why not just put the value in the program? • Note: The compiler automatically defines the type to the constant identifier by looking at the value assigned to it.

  2. Reserved words • Certain words have special meaning to the compiler. Therefore these words cannot be used as constant or variable identifiers. • We have seen some examples: • DIV, MOD • VAR, CONST • PROGRAM, BEGIN, END

  3. String Variables • Note: This is not part of the Pascal standard. It was added to Turbo Pascal (and some other Pascal compilers) • To declare a string variable we could write: • VAR Country: string[13]; • To assign a value to a string variable we could write: • Country := ‘United States’;

  4. More about integers • What if you need an integer larger than 32767? • Using integer type would be incorrect • another type called LongInt is used • -2147483648 -> 2147483647 • other integer types are: • byte (0->255) • shortint (-128->127) • word (0->65535)

  5. More about reals • Reals also have other types • real 6 bytes 11 to 12 digits • single 4 bytes 7 to 8 digits • double 8 bytes 15 to 16 digits • extended 10 bytes 19 to 20 digits

  6. Chapter 3 topics • write / writeln • readln • VAR declaration • CONST definition • assignment statement (including arithmetic)

  7. Formatting output: integers • Field: a group of columns in which results are printed is called a field • Field width: The number of columns in the field • writeln(IntId:##) • IntId is an integer identifier or value • ## is the rightmost column to print the integer (Compiler will ignore this value if its smaller than number of digits) • can be written as any integer expression • default is one

  8. Formatting output: reals • Writeln (RealId:#1:#2) • RealId is a real identifier or value • #1 is the rightmost column to print the real • #2 is the number of digits you want on the right of the decimal point. • If #2 is omitted, scientific notation is used

  9. Formatting output: strings • Writeln (stringId:##) • stringId can be a string or character identifier or value • ## is the rightmost column for the string to be printed in

  10. Formatting output: Boolean • Similar to strings • note: Although the compiler is not Cap sensitive, it always prints Boolean values in all CAPS.

More Related