Curly Braces ({, })

Introduction

Curly braces (also referred to as just “braces” or as “curly brackets”) are a major part of the C and C++ programming languages. They are used in several different constructs, outlined below, and this can sometimes be confusing for beginners.

An opening curly brace, { must always be followed by a closing curly brace }. This is a condition that is often referred to as the braces being balanced. The Maple IDE (integrated development environment) includes a convenient feature to check the balance of curly braces. Just select a brace, or even click the insertion point immediately following a brace, and its companion will be highlighted[1].

Beginning programmers, and programmers coming to C++ from languages without braces, often find using them confusing or daunting.

Because the use of the curly brace is so varied, it is good programming practice to type the closing brace immediately after typing the opening brace when inserting a construct which requires curly braces. Then insert some blank lines between your braces and begin inserting statements. Your braces, and your attitude, will never become unbalanced.

Unbalanced braces can often lead to cryptic, impenetrable compiler errors that can sometimes be hard to track down in a large program. Because of their varied usages, braces are also incredibly important to the syntax of a program and moving a brace one or two lines will usually dramatically affect the meaning of a program.

The main uses of curly braces

Functions:

// a function body needs braces around it
void myFunction(datatype argument) {
  // ... function body goes in here ...
}

Loops (see the while, for, and do/while loop reference pages for more information):

// you should put braces around the body of a loop:

while (boolean expression) {
   // code inside the loop goes here
}

for (initialisation; termination condition; incrementing expr) {
   // code inside the loop goes here
}

do {
   // code inside the loop goes here
} while (boolean expression);

Conditional statements (see the if statement reference page for more information):

// you should put braces around the body of an "if", "else if",
// or "else":

if (boolean expression) {
    // code inside the "if"
}
else if (boolean expression) {
    // code inside the "else if"
}
else {
    // code inside the "else"
}

Switch statements (see the switch statement reference page for more information):

switch (var) {
case 1:
    doThing1();
    break;
case 2:
    doThing2();
    break;
}

Footnotes

[1]	At present this feature is slightly buggy as the IDE will often find (incorrectly) a brace in text that has been commented out.

License and Attribution

This documentation page was adapted from the Arduino Reference Documentation, which is released under a Creative Commons Attribution-ShareAlike 3.0 License.