C ++ primer learning note (3.1) namespace using statement

Chapter 3 Standard Library types

3.1TheUsingStatement

In general, the header file should only define the necessary things.

 
# Include <iostream> Using STD: CIN; Using STD: cout; Using STD: Endl; int main () {// some codes .....}
 

C ++StandardProgramAll identifiers in the library are defined inSTDOfNamespace.

Therefore, it is more convenient to useUsing namespace STD;

For example:

# Include <iostream>

Using namespace STD;

In this way, the namespaceSTDAll identifiers defined in !! You don't have to write them one by one !!

Exercise3.1

//Use appropriateUsingStatement, insteadSTDPrefix: calculates the result of a given power of a given number.

 
# Include <iostream> Using STD: CIN; Using STD: cout; Using STD: Endl; int main () {int Val, pow, Res = 1; cout <"enter two numbers" <Endl; CIN> Val> POW; For (int cnt = 1; CNT <= POW; CNT ++) res = res * val; cout <"the result of" <Val <"^" <POW <"is" <res <Endl; return 0 ;}