C++ LANGUAGE GOTO STATEMENT PAGE 55

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C++ LANGUAGE GOTO STATEMENT

goto Statement 


A goto statement provides an unconditional jump from 
the goto to a labeled statement in the same function. 
NOTE: Use of goto statement is highly discouraged because 
it makes difficult to trace the control flow of a program, 
making the program hard to understand and hard to modify. 
Any program that uses a goto can be rewritten so that it 
doesn't need the goto. 

Syntax 

The syntax of a goto statement in C++ is: 
goto label; 
.. 
. 
label: statement; 
Where label is an identifier that identifies a labeled 
statement. A labeled statement is any statement that is 
preceded by an identifier followed by a colon (:). 

Flow Diagram 
 
Example 
#include <iostream> 
using namespace std; 
  
int main () 
{ 
   // Local variable declaration: 
   int a = 10; 
 
   // do loop execution 
   LOOP:do 
   { 
       if( a == 15) 
       { 
          // skip the iteration. 
          a = a + 1; 
          goto LOOP; 
       } 
       cout << "value of a: " << a << endl; 
       a = a + 1; 
   }while( a < 20 ); 
  
   return 0; 
} 
When the above code is compiled and executed, it produces the following result: 
value of a: 10 
value of a: 11 
value of a: 12 
value of a: 13 
value of a: 14 
value of a: 16 
value of a: 17 
value of a: 18 
value of a: 19 
One good use of goto is to exit from a deeply nested routine. 
For example, consider the following code fragment: 

for(...) { 
   for(...) { 
      while(...) { 
         if(...) goto stop; 
         . 
         . 
         . 
      } 
   } 
} 

stop: 

cout << "Error in program.\n"; 

Eliminating the goto would force a number of additional tests to 
be performed. A simplebreak statement would not work here, because 
it would only cause the program to exit from the innermost loop.