An iterator to the first element in the container.

If a map object is const-qualified, the function returns a const_iterator. Otherwise, it returns an iterator.

// Create a map and insert some values
std::map<char,int> mymap;
mymap['b'] = 100;
mymap['a'] = 200;
mymap['c'] = 300;

// Iterate over all tuples
for (std::map<char,int>::iterator it = mymap.begin(); it != mymap.end(); ++it)
    std::cout << it->first << " => " << it->second << '\\n';

Output:

a => 200

b => 100

c => 300