C++ Loop Types for Efficient Programming
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C++ Loop Types
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There may be a situation, when you need to
execute a block of code several number of times.
In general, statements are executed sequentially:
The first statement in a function is executed first,
followed by the second, and so on.
•
Loops can execute a block of code as long as a
specified condition is reached.
•
Loops are handy because they save time, reduce
errors, and they make code more readable.
•
C++ programming language provides the
following type of loops to handle looping
requirements.
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The
while
loop repeats a statement or group of
statements while a given condition is true. It tests
the condition before executing the loop body.
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Syntax:
while (condition)
{// code block to be executed
}
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In the example below, the code in the loop will
run, over and over again, as long as a variable (i)
is less than 5.
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C++ While Loop(cont'd.)
#include <iostream>
using namespace std;
int main()
{int i = 0;
while (i < 5)
{cout << i << "\n";
i++;
}
return 0;
}
•
Note:
Do not forget to increase the variable used in the
condition, otherwise the loop will never end!
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The
do/while
loop is a variant of the while loop. This
loop will execute the code block once, before checking
if the condition is true, then it will repeat the loop as
long as the condition is true.
•
Syntax:
Do
{// code block to be executed
}
while (condition);
•
The example below uses a do/while loop. The loop will
always be executed at least once, even if the condition
is false, because the code block is executed before the
condition is tested:
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C++ Do/While Loop(cont'd.)
#include <iostream>
using namespace std;
int main()
{int i = 0;
do
{cout << i << "\n";
i++;
}
while (i < 5);
return 0;
}
•
Do not forget to increase the variable used in the condition,
otherwise the loop will never end!
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C++ For Loop
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A
for
loop is a repetition control structure that
allows you to efficiently write a loop that needs
to execute a specific number of times.
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When you know exactly how many times you
want to loop through a block of code, use the
for
loop instead of a
while
loop.
•
Syntax:
for (statement 1; statement 2; statement 3)
{// code block to be executed
}
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C++ For Loop(cont'd.)
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Statement 1 is executed (one time)
before the execution of the code block.
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Statement 2 defines the condition for
executing the code block.
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Statement 3 is executed (every time)
after the code block has been executed.
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The example below will print the
numbers 0 to 4.
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#include <iostream>
using namespace std;
int main()
{for (int i = 0; i < 5; i++)
{cout << i << "\n";
}
return 0;
}
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Example explained.
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Statement 1 sets a variable before the loop
starts (int i = 0).
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Statement 2 defines the condition for the loop
to run (i must be less than 5). If the condition
is true, the loop will start over again, if it is
false, the loop will end.
•
Statement 3 increases a value (i++) each time
the code block in the loop has been executed.
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C++ For Loop(cont'd.)
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Another Example:
•
This example will only print even values between 0 and
10:
#include <iostream>
using namespace std;
int main()
{for (int i = 0; i <= 10; i = i + 2)
{cout << i << "\n";
}
return 0;
}
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We have already seen the
break
statement was used to "jump out"
of a switch statement.
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The
break
statement can also be used to jump out of a loop.
#include <iostream>
using namespace std;
int main()
{for (int i = 0; i < 10; i++)
{if (i == 4)
{break;
}
cout << i << "\n";
}
return 0;
}
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This example jumps out of the loop
when i is equal to 4.
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The
continue
statement breaks one iteration (in the loop), if a
specified condition occurs, and continues with the next iteration in
the loop.
#include <iostream>
using namespace std;
int main()
{for (int i = 0; i < 10; i++)
{if (i == 4)
{continue;
}
cout << i << "\n";
}
return 0;
}
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This example skips the value of 4:
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Break Example:
#include <iostream>
using namespace std;
int main()
{int i = 0;
while (i < 10)
{cout << i << "\n";
i++;
if (i == 4)
{break;
}
}
return 0;
}
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Break and Continue in While Loop(cont'd.)
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Continue Example:
#include <iostream>
using namespace std;
int main()
{int i = 0;
while (i < 10)
{if (i == 4)
{i++;
continue;
}
cout << i << "\n";
i++;
}
return 0;
}
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A goto statement provides an unconditional jump
from the goto to a labeled statement in the same
function.
•
Example:
#include <iostream>
using namespace std;
int main ()
{int a = 10;
do
{if( a == 15)
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C++ goto statement(cont'd.)
{a++;
goto STOP;
}
cout << "value of a: " << a << endl;
a++;
}
while( a < 20 );
STOP:
return 0;
}
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A loop becomes infinite loop if a condition never
becomes false. The for loop is traditionally used
for this purpose. Since none of the three
expressions that form the ‘for’ loop are required,
you can make an endless loop by leaving the
conditional expression empty.
•
When the conditional expression is absent, it is
assumed to be true. You may have an
initialization and increment expression, but C++
programmers more commonly use the ‘for (;;)’
construct to signify an infinite loop.
•
NOTE − You can terminate an infinite loop by
pressing Ctrl + C keys.
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The Infinite Loop(cont'd.)
#include <iostream>
using namespace std;
int main()
{for( ; ; )
{cout<<"This loop will run forever.\n";
}
return 0;
}
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This chapter introduces C++ loop types to handle repetitive tasks efficiently. Learn about while loops and do/while loops with examples and syntax explanations. Understanding these loop structures is essential for writing clear and readable code in C++.
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Presentation Transcript
Introduction to programming with C++ C++ Introduction Chapter Seven Yasser Abdulhaleem Abdulkareem Almadany 1
C++ Loop Types There may be a situation, when you need to execute a block of code several number of times. In general, statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on. Loops can execute a block of code as long as a specified condition is reached. Loops are handy because they save time, reduce errors, and they make code more readable. C++ programming language provides the following type of loops to handle looping requirements. Yasser Abdulhaleem Abdulkareem Almadany 2
C++ While Loop The while loop repeats a statement or group of statements while a given condition is true. It tests the condition before executing the loop body. Syntax: while (condition) { // code block to be executed } In the example below, the code in the loop will run, over and over again, as long as a variable (i) is less than 5. Yasser Abdulhaleem Abdulkareem Almadany 3
C++ While Loop(cont'd.) #include <iostream> using namespace std; int main() { int i = 0; while (i < 5) { cout << i << "\n"; i++; } return 0; } Note: Do not forget to increase the variable used in the condition, otherwise the loop will never end! Yasser Abdulhaleem Abdulkareem Almadany 4
C++ Do/While Loop The do/while loop is a variant of the while loop. This loop will execute the code block once, before checking if the condition is true, then it will repeat the loop as long as the condition is true. Syntax: Do { // code block to be executed } while (condition); The example below uses a do/while loop. The loop will always be executed at least once, even if the condition is false, because the code block is executed before the condition is tested: Yasser Abdulhaleem Abdulkareem Almadany 5
C++ Do/While Loop(cont'd.) #include <iostream> using namespace std; int main() { int i = 0; do { cout << i << "\n"; i++; } while (i < 5); return 0; } Do not forget to increase the variable used in the condition, otherwise the loop will never end! Yasser Abdulhaleem Abdulkareem Almadany 6
C++ For Loop A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times. When you know exactly how many times you want to loop through a block of code, use the for loop instead of a while loop. Syntax: for (statement 1; statement 2; statement 3) { // code block to be executed } Yasser Abdulhaleem Abdulkareem Almadany 7
C++ For Loop(cont'd.) Statement 1 is executed (one time) before the execution of the code block. Statement 2 defines the condition for executing the code block. Statement 3 is executed (every time) after the code block has been executed. The example below will print the numbers 0 to 4. Yasser Abdulhaleem Abdulkareem Almadany 8
C++ For Loop(cont'd.) #include <iostream> using namespace std; int main() { for (int i = 0; i < 5; i++) { cout << i << "\n"; } return 0; } Yasser Abdulhaleem Abdulkareem Almadany 9
C++ For Loop(cont'd.) Example explained. Statement 1 sets a variable before the loop starts (int i = 0). Statement 2 defines the condition for the loop to run (i must be less than 5). If the condition is true, the loop will start over again, if it is false, the loop will end. Statement 3 increases a value (i++) each time the code block in the loop has been executed. Yasser Abdulhaleem Abdulkareem Almadany 10
C++ For Loop(cont'd.) Another Example: This example will only print even values between 0 and 10: #include <iostream> using namespace std; int main() { for (int i = 0; i <= 10; i = i + 2) { cout << i << "\n"; } return 0; } Yasser Abdulhaleem Abdulkareem Almadany 11
C++ Break We have already seen the break statement was used to "jump out" of a switch statement. The break statement can also be used to jump out of a loop. #include <iostream> using namespace std; int main() { for (int i = 0; i < 10; i++) { if (i == 4) { break; } cout << i << "\n"; } return 0; } Yasser Abdulhaleem Abdulkareem Almadany This example jumps out of the loop when i is equal to 4. 12
C++ Continue The continue statement breaks one iteration (in the loop), if a specified condition occurs, and continues with the next iteration in the loop. #include <iostream> using namespace std; int main() { for (int i = 0; i < 10; i++) { if (i == 4) { continue; } cout << i << "\n"; } return 0; } Yasser Abdulhaleem Abdulkareem Almadany This example skips the value of 4: 13
Break and Continue in While Loop Break Example: #include <iostream> using namespace std; int main() { int i = 0; while (i < 10) { cout << i << "\n"; i++; if (i == 4) { break; } } return 0; } Yasser Abdulhaleem Abdulkareem Almadany 14
Break and Continue in While Loop(cont'd.) Continue Example: #include <iostream> using namespace std; int main() { int i = 0; while (i < 10) { if (i == 4) { i++; continue; } cout << i << "\n"; i++; } return 0; } Yasser Abdulhaleem Abdulkareem Almadany 15
C++ goto statement A goto statement provides an unconditional jump from the goto to a labeled statement in the same function. Example: #include <iostream> using namespace std; int main () { int a = 10; do { if( a == 15) Yasser Abdulhaleem Abdulkareem Almadany 16
C++ goto statement(cont'd.) { a++; goto STOP; } cout << "value of a: " << a << endl; a++; } while( a < 20 ); STOP: return 0; } Yasser Abdulhaleem Abdulkareem Almadany 17
The Infinite Loop A loop becomes infinite loop if a condition never becomes false. The for loop is traditionally used for this purpose. Since none of the three expressions that form the for loop are required, you can make an endless loop by leaving the conditional expression empty. When the conditional expression is absent, it is assumed to be true. You may have an initialization and increment expression, but C++ programmers more commonly use the for (;;) construct to signify an infinite loop. NOTE You can terminate an infinite loop by pressing Ctrl + C keys. Yasser Abdulhaleem Abdulkareem Almadany 18
The Infinite Loop(cont'd.) #include <iostream> using namespace std; int main() { for( ; ; ) { cout<<"This loop will run forever.\n"; } return 0; } Yasser Abdulhaleem Abdulkareem Almadany 19
