by John
Kopp
Welcome to About.com's C++ tutorial. This lesson introduces
conditional processing. In previous tutorials, all the code in
the examples executed, that is, from the first line of the
program to the last, every statement was executed in the order it
appeared in the source code. This may be correct for some
programs, but others need a way to choose which statements
will be executed or run. Conditional processing extends the
usefulness of programs by allowing the use of simple logic or
tests to determine which blocks of code are executed. In this
lesson, a simple guessing game will be developed to illustrate
the use of conditional execution.
The if statement is used to conditionally execute a
block of code based on whether a test condition is true. If
the condition is true the block of code is executed, otherwise
it is skipped.
#include <iostream> using namespace
std;
int
main() {
int number =
5; int
guess;
cout << "I
am thinking of a number between 1 and 10" <<
endl; cout << "Enter
your guess, please " <<
endl; cin >>
guess; if (guess ==
number) { cout
<< "Incredible, you are correct" <<
endl; }
return
0; } |
Please try compiling and executing the above. The "==" is
called a relational operator. Relational
operators, ==, !=, >, >=, <, and <=, are used to
compare two operands. The program works, but it needs some
improvements. If the user enters 5 as a choice, he gets back a
nice message, "Incredible, you are correct". But what happens
if the user puts in an incorrect choice? Nothing. No message,
no suggestions, nothing. Luckily, for our program user, C++
has a solution.
The else statement provides a way to execute one
block of code if a condition is true, another if it is
false.
#include <iostream> using namespace
std;
int
main() {
int number =
5; int
guess;
cout << "I
am thinking of a number between 1 and 10" <<
endl; cout << "Enter
your guess, please "; cin
>> guess; if (guess ==
number) { cout
<< "Incredible, you are correct" <<
endl; } else { cout
<< "Sorry, try again" <<
endl; }
return
0; } |
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