perl_02_IntroductionPerl.ppt

1、1,Chapter 2 Introduction to Programming in Perl,Outline2.1Introduction2.2Simple Programs that Display lines of Text2.2.1A Simple Program: Displaying a Line of Text2.2.2Executing the Program2.2.3A Simple Program: Printing Several Lines of Text2.3Another Simple Program: Adding Two Integers2.4Memory Co

2、ncepts2.5Scalar Values and Scalar Variables2.6Arithmetic Operators2.7Assignment Operators2.8Increment and Decrement Operators2.9Decision Making: Equality and Relational Operators 2.10Confusing Equality (=) and Assignment (=) Operators2.11String Operators2.12Numeric and String Context2.13Internet and

3、 world wide Web Resources,2,Welcome to Perl!,3,4,1. Welcome to Perl! 2. Welcome to Perl! 3. Welcome to Perl! 4. Welcome to Perl! 5. Welcome to Perl! 6. Welcome to Perl!,5,1#!/usr/bin/perl,2# Fig. 2.4: fig02_04.pl,3# A simple addition program,4,5# prompt user for first number,6print Please enter firs

4、t number:n;,7$number1 = ;,8chomp $number1; # remove n from input,9,10print Please enter second number:n;,11$number2 = ;,12chomp $number2; # remove n from input,13,14$sum = $number1 + $number2;,15,16print The sum is $sum.n;,Please enter first number: 45 Please enter second number: 72 The sum is 117.,

5、6,7,8,9,10,11,12,13,5 5 6 5 6 6,14,15,16,17,Please enter first integer: 3 Please enter second integer: 7 The integers satisfy these relationships: 3 is not equal to 7. 3 is less than 7. 3 is less than or equal to 7.,Please enter first integer: 22 Please enter second integer: 12 The integers satisfy

6、these relationships: 22 is not equal to 12. 22 is greater than 12. 22 is greater than or equal to 12.,Please enter first integer: 7 Please enter second integer: 7 The integers satisfy these relationships: 7 is equal to 7. 7 is less than or equal to 7. 7 is greater than or equal to 7.,18,19,1#!/usr/b

7、in/perl,2# Fig. 2.19: fig02_19.pl,3# Program to illustrate numeric and string context, and undef,4,5$string = Top 10;,6$number = 10.0;,7print Number is 10.0 and string is Top 10nn;,8,9$add = $number + $string; # 10 (not 20),10print Adding a number and a string: $addn;,11,12$concatenate = $number . $

8、string; # 10Top 10,13 # (not 10.0Top 10),14print Concatenating a number and a string: $concatenaten;,15,16$add2 = $concatenate + $add; # 20 (not 30, not 1020),17print Adding the previous two results: $add2nn;,18,19$undefAdd = 10 + $undefNumber;,20print Adding 10 to an undefined variable: $undefAddn;,21,22print Printing an undefined variable: $undefVariable(end)n;,Number is 10.0 and string is Top 10 Adding a number and a string: 10 Concatenating a number an