Object-oriented Software in Ada 95

32 Ada introduction: Part 1
A character variable may be declared which can hold a character from the Ada character set. The following
case statement would print out a classification of the character held in the object Ch.
Ch := 'a';
case Ch is
when '0' | '1' | '2' | '3' | '4' |
'5' | '6' | '7' | '8' | '9' =>
Put("Character is a digit");
when 'A' .. 'Z' =>
Put("Character is upper case English letter");
when 'a' .. 'z' =>
Put("Character is lower case English letter");
when others =>
Put("Not an English letter or digit");
end case;
New_Line;
In this case statement two ways of combining case labels are introduced.
Case component Description Explanation
| Or For example, '0' | '1' will match the
character '0' or the character '1'
.. Range For example, 'A' .. 'Z' will match any
character in the range Capital A to Capital Z.
The fragment of program code combined with appropriate declarations and compiled would produce when
run:
Character is lower case English letter
3.9 Input and output
In Ada, input and output are performed by a variety of standard packages. The full implications of the package
construct are discussed fully in Chapters 5 and 17 which describe in detail the I/O packages. For the moment, the
discussion about input and output will concentrate solely on character data.
Text is output to the terminal using the put procedure. This procedure may take a formal parameter which is
either a character or a character string. For example, to output hello the user could write either:
Put( "Hello" );
or
Put('h'); Put('e'); Put('l'); Put('l'); Put('o');
Note:
A string is use to represent a sequence of characters. A string is enclosed in " " whilst a character is
enclosed in ' '. In this way the compiler can distinguish between a character 'A'and a string of a single
character "A".
© M A Smith - May not be reproduced without permission