[Control Structures]
Description
The for
statement is used to repeat a block of statements enclosed in curly braces. An increment counter is usually used to increment and terminate the loop. The for
statement is useful for any repetitive operation and is often used in combination with arrays to operate on collections of data/pins.
There are three parts to the for
loop header:
for (initialization ; condition ; increment) { //statement(s); }
The initialization happens first and exactly once. Each time through the loop, the condition is tested; if it’s true, the statement block, and the increment is executed, then the condition is tested again. When the condition becomes false, the loop ends.
Example Code
// Dim an LED using a PWM pin int PWMpin = 10; // LED in series with 470 ohm resistor on pin 10 void setup() { // no setup needed } void loop() { for (int i=0; i <= 255; i++) { analogWrite(PWMpin, i); delay(10); } }
Coding Tips
The C for
loop is much more flexible than for
loops found in some other computer languages, including BASIC. Any or all of the three header elements may be omitted, although the semicolons are required. Also the statements for initialization, condition, and increment can be any valid C statements with unrelated variables, and use any C datatypes including floats. These types of unusual for
statements may provide solutions to some rare programming problems.
For example, using a multiplication in the increment line will generate a logarithmic progression:
for (int x = 2; x < 100; x = x * 1.5) { println(x); }
Generates: 2,3,4,6,9,13,19,28,42,63,94
Another example, fade an LED up and down with one for
loop:
void loop() { int x = 1; for (int i = 0; i > -1; i = i + x) { analogWrite(PWMpin, i); if (i == 255) x = -1; // switch direction at peak delay(10); } }
See also
- [Language] while
Language Reference Home
The text of the 86Duino reference is a modification of the Arduino reference and is licensed under a Creative Commons Attribution-ShareAlike 3.0 License. Code samples in the reference are released into the public domain.