"The string class of the standard library provides three member functions to get a character array of type C from a string: C_ str（）、data（）、copy（p，n）。
C language strcpy() usage
This is a library function for copying strings in C language. The function declaration is included in the header file "string. H" specially dealing with strings:
char * strcpy（ char * dst， const char * src ）;
This function copies the string SRC into an allocated string space DST, including the null character marking the end of the string. DST is returned if the operation is successful, otherwise null is returned
You should note that the length of your second string SRC + 1 (+ 1 is because the string ends with a null symbol) cannot exceed the size of the space you have opened up for DST, otherwise the null characters in SRC cannot be copied into DST, and your DST becomes a character array, not a string. In that case, if you have a printf or puts statement or something behind you, you should print out the DST, It will cross the line because there is no empty character to mark the end of the string.
For example:
Define a string char a [20], and a string c [] = "I am a teacher!";
Copy C to a and use it like this: strcpy (a, c);
This function is contained in the header file "string. H".
Program code:
#include《string.h》
#include《iostream.h》
void main（）
{char a［20］，c［］=“i am teacher！”;
strcpy（a，c）;
cout《《a《《endl;
}
You see:
char a［20］ = “abcde”
Strcpy (& A [1], a) function is copied character by character,
First copy the first character, a [0] = = 'a'; a［1］ = a［0］; That is, a [1] = 'a';
Then copy the second character, a [1] = = 'a'; a［2］ = a［1］; That is, a [2] = 'a';
And so on!!! A [0] = 'a' is useless. In fact, the initial a [0] is equal to 'a'!
copy（p，n，size_ type _ Off = 0): copy up to n characters from a string type object into the space pointed to by the character pointer P. By default, it starts from the first character, but you can also specify the starting position (remember to start from 0). Returns the character that was actually copied from the object------ The user should ensure that the space pointed to by P is enough to store n characters.
// basic_ string_ copy.cpp
// compile with： /EHsc /W3
#include 《string》
#include 《iostream》
int main（ ）
{
using namespace std;
string str1 （ “1234567890” ）;
basic_ string 《char》：：iterator str_ Iter;
char array1 ［ 20 ］ = { 0 };
char array2 ［ 10 ］ = { 0 };
basic_ string 《char》：： pointer array1Ptr = array1;
basic_ string 《char》：： value_ type *array2Ptr = array2;
cout 《《 “The original string str1 is： ”;
for （ str_ Iter = str1.begin（ ）; str_ Iter ！= str1.end（ ）; str_ Iter++ ）
cout 《《 *str_ Iter;
cout 《《 endl;
basic_ string 《char》：： size_ type nArray1;
// Note： string：：copy is potenTIally unsafe， consider
// using string：：_ Copy_ s instead.
nArray1 = str1.copy （ array1Ptr ， 12 ）; // C4996
cout 《《 “The number of copied characters in array1 is： ”
《《 nArray1 《《 endl;
cout 《《 “The copied characters array1 is： ” 《《 array1Ptr 《《 endl;
basic_ string 《char》：： size_ type nArray2;
// Note： string：：copy is potenTIally unsafe， consider
// using string：：_ Copy_ s instead.
nArray2 = str1.copy （ array2Ptr ， 5 ， 6 ）; // C4996
cout 《《 “The number of copied characters in array2 is： ”
《《 nArray2 《《 endl;
cout 《《 “The copied characters array2 is： ” 《《 array2Ptr 《《 endl;
////Be sure to make array3 have enough space
//char array3［5］={0};
//basic_ string《char》：：pointer array3Ptr=array3;
//basic_ string《char》：：size_ type nArray3;
//nArray3 = str1.copy（array3，9）; // Error!!!!
//cout《《“The number of copied characters in array3 is： ”
// 《《nArray3《《endl;
//cout《《“The copied characters array3 is： ”《《array3Ptr《《endl;
}
For the last commented part above, although there are no errors in compilation, errors will be generated during runtime: stack around the variable 'array3' was corrupted
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