Learn C++ - C++ if
The syntax for the if statement is similar to the that of the while syntax:
if (test-condition) statement
A true test-condition causes the program to execute statement, which can be a single statement or a block.
A false test-condition causes the program to skip statement.
An if test condition is type cast to a bool value, so zero becomes false and nonzero becomes true.
The entire if construction counts as a single statement.
Example
#include <iostream>
int main() //from ww w . j a v a 2s . c om
{
using std::cin;
using std::cout;
char ch;
int spaces = 0;
int total = 0;
cin.get(ch);
while (ch != '.') // quit at end of sentence
{
if (ch == ' ') // check if ch is a space
++spaces;
++total; // done every time
cin.get(ch);
}
cout << spaces << " spaces, " << total;
cout << " characters total in sentence\n";
return 0;
}
The code above generates the following result.
The if else Statement
An if else statement lets a program decide which of two statements or blocks is executed.
The if else statement has this general form:
if (test-condition) statement1 else statement2
If test-condition is true, or nonzero, the program executes statement1 and skips over statement2.
Otherwise, when test-condition is false, or zero, the program skips statement1 and executes statement2 instead.
#include <iostream>
int main() { //from w w w .j av a2 s . co m
char ch;
std::cout << "Type, and I shall repeat.\n";
std::cin.get(ch);
while (ch != '.')
{
if (ch == '\n')
std::cout << ch; // done if newline
else
std::cout << ++ch; // done otherwise
std::cin.get(ch);
}
return 0;
}
The code above generates the following result.
using if else if else
#include <iostream>
const int Fave = 27;
int main() //from w w w . j a v a2 s.c o m
{
using namespace std;
int n;
cout << "Enter a number in the range 1-100 to find ";
cout << "my favorite number: ";
do
{
cin >> n;
if (n < Fave)
cout << "Too low -- guess again: ";
else if (n > Fave)
cout << "Too high -- guess again: ";
else
cout << Fave << " is right!\n";
} while (n != Fave);
return 0;
}
The code above generates the following result.
