Address/pointer and string

Original: Address/pointer and string

When doing your homework today, I found one of the following problems.

The home page is this self-compiled strncpy function:

#include "ctype.h" #include "stdlib.h" #include "string.h" #include "windows.h" int main () {char *strata (char S1[],char s2[ ],int n); char nam1[41]= "Das"; char nam2[41]= "wo shi yi ge da sha bi"; Strata (nam1,nam2,4);p UTS (NAM1); System ("pause"); return 0;} Char *strata (char s1[],char s2[],int n) {int I;char *prt=s1;if (n>strlen (S2)) return "-1"; else{s2[n]= '; for (i=0;i <n;i++) s1[i]=s2[i];}}

Forget it all: The address of the array is passed in the argument.

Slowly found Char *prt=s1;

The array name itself is the pointer constant;

A string can assign a value to an address problem:

For statement char *a= "Hello";

For this declaration, the misconception is that a character pointer is declared (it points to a location) and the string is assigned to the address pointed to by the pointer expression "*a". But the positive solution is: After a character pointer is declared, it is assigned to the pointer variable A with the address of the first character of the string constant. That is, the correct order is: 1. Allocate memory to a character pointer; 2. Allocate memory to a string; 3. Assign the first address of the string to a character pointer; Here are two points to consider:①*a just points to a character. Examples are as follows:

[C + +]View Plaincopyprint?

2. #include <stdio.h>
4. #include <stdlib.h>
8. int main (void) {
10. char *a="BCD";
12. printf ("Output character:%c/n", *a);  /* Output character, using "%c" */<br> printf ("Output character:%c/n", * (a+1)); / * Output characters, using "%c" * /
14. printf ("Output string:%s/n", a); / * Output string, use "%s", and a cannot have an asterisk "*" * /
16. System ("pause"); / * In order to see the output results * /
18. }
20. /* Run the results as follows:
22. Output character:b<br> output character: C
24. Output string: bcd*/

② If a string constant appears in an expression, the value represented is the address of the first character of the string constant. So "Hello" just stands for its address.            

1. Char *a;
2. a="Hello"; /* Here the string "Hello" represents only the address of its first character * /

There are no string variables in C, so character arrays are generally used when storing string constantsto store.
The array is a contiguous storage space, where two important quantities are recorded: the first address and the space size.
    and the pointer does not care about its length, as long as the record ere address is OK.

    Char *a;//request space Address
    a= "Hello";//a points to ' H ', and memory is open.
     for ease of understanding, some places can be "equivalent" to the address/pointer and the string, the address/pointer to the variable is the first character of the string.

     If you have a better understanding, I hope you will review

Address/pointer and string