Statements are fragments of the C++ program that are executed in sequence. The body of any function is a sequence of statements. For example:

int main(){int n=1;// declaration statement    n= n+1;// expression statementstd::cout<<"n = "<< n<<'\n';// expression statementreturn0;// return statement}

C++ includes the following types of statements:

• Labeled statements
• Expression statements
• Compound statements
• Selection statements
• Iteration statements
• Jump statements

• Declaration statements
• try blocks

[edit]Labeled statements

A labeled statement labels a statement for control flow purposes.

[edit]Labels

label is defined as

A label with an identifier declared inside a function matches all goto statements with the same identifier in that function, in all nested blocks, before and after its own declaration.

Two labels in a function must not have the same identifier.

Labels are not found byunqualified lookup: a label can have the same name as any other entity in the program.

void f(){{goto label;// label in scope even though declared later        label:// label can appear at the end of a block standalone since C++23}goto label;// label ignores block scope} void g(){goto label;// error: label not in scope in g()}

[edit]Control-flow-limited statements

The following statements arecontrol-flow-limited statements :

• Thecompound-statement of atry block.
• Thecompound-statement of ahandler.

For each control-flow-limited statementS:

• Allgoto target labels delcared inS can only be referred to by statements inS.
• Eachcase ordefault label appearing withinS can only be associated with aswitch statement withinS.

[edit]Expression statements

An expression statement is an expression followed by a semicolon.

Most statements in a typical C++ program are expression statements, such as assignments or function calls.

An expression statement without an expression is called anull statement. It is often used to provide an empty body to afor orwhile loop.It can also be used to carry a label in the end of a compound statement.(until C++23)

[edit]Compound statements

A compound statement orblock groups a sequence of statements into a single statement.

When one statement is expected, but multiple statements need to be executed in sequence (for example, in anif statement or a loop), a compound statement may be used:

if(x>5)// start of if statement{// start of blockint n=1;// declaration statementstd::cout<< n;// expression statement}// end of block, end of if statement

Each compound statement introduces its own blockscope; variables declared inside a block are destroyed at the closing brace in reverse order:

int main(){// start of outer block{// start of inner blockstd::ofstream f("test.txt");// declaration statement        f<<"abc\n";// expression statement}// end of inner block, f is flushed and closedstd::ifstream f("test.txt");// declaration statementstd::string str;// declaration statement    f>> str;// expression statement}// end of outer block, str is destroyed, f is closed

[edit]Selection statements

A selection statement chooses between one of several control flows.

[edit]Iteration statements

An iteration statement repeatedly executes some code.

[edit]Jump statements

A jump statement unconditionally transfers control flow.

Note: for all jump statements, transfer out of a loop, out of a block, or back past an initialized variable with automatic storage duration involves the destruction of objects with automatic storage duration that are in scope at the point transferred from but not at the point transferred to. If multiple objects were initialized, the order of destruction is the opposite of the order of initialization.

[edit]Declaration statements

A declaration statement introduces one or more identifiers into a block.

[edit]try blocks

Atry block catches exceptions thrown when executing other statements.

[edit]Substatements

Asubstatement of a statement is one of the following:

• For alabeled statement, itsstatement .
• For acompound statement, any statement of itsstatement... .
• For aselection statement, any of itsstatement  orcompound-statement (since C++23).
• For aniteration statement, itsstatement .

A statementS1encloses a statementS2 if any of the following conditions is satisfied:

• S2 is a substatement ofS1
• S1 is a selection statement or iteration statement, andS2 is theinit-statement ofS1.
• S1 is atry block, andS2 is either itscompound-statement or thecompound-statement of anyhandler in itshandler-seq .
• S1 encloses a statementS3 andS3 enclosesS2.

A statementS1 isenclosed by a statementS2 ifS2 enclosesS1.

[edit]See also

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