Memset memcpy strcpy

 

 

# Include "memory. H"

Memset is used to set all memory spaces to a specific character. It is generally used to initialize the defined string to ''or '/0'. For example, char a [100]. memset (A, '/0', sizeof ());

Memcpy is used for memory copying. You can use it to copy any data type object and specify the length of the copied data. For example, char a [100], B [50]; memcpy (B, a, sizeof (B); note that if sizeof (a) is used, the memory address of B may overflow.

Strcpy can only copy strings. It ends copying when '/0' is encountered. For example, char a [100], B [50]; strcpy (A, B ); if strcpy (B, A) is used, check whether the length of the string in A (before the first '/0') exceeds 50 bits. If it exceeds, this will cause memory address overflow of B.

Strcpy
Prototype: extern char * strcpy (char * DEST, char * SRC );
Usage: # include <string. h>
Function: Copies the string ending with null indicated by Src to the array indicated by DeST.
Note: The memory areas specified by Src and DEST cannot overlap and DEST must have sufficient space to accommodate SRC strings.
Returns the pointer to DeST.
Memcpy
Prototype: extern void * memcpy (void * DEST, void * SRC, unsigned int count );
Usage: # include <string. h>
Function: copy count bytes from the memory area indicated by Src to the memory area indicated by DeST.
Note: the memory areas specified by Src and DEST cannot overlap. The function returns a pointer to DeST.
Memset
Prototype: extern void * memset (void * buffer, int C, int count );
Usage: # include <string. h>
Function: sets the first count byte of the memory area referred to by buffer to character C.
Note: The pointer to the buffer is returned.

 

1. Void * memset (void * s, int C, size_t N)
Purpose: set the value of the first n Bytes of the memory space S to the value c.

2. Example

Main (){
Char * s = "golden Global View ";

Clrscr ();

Memset (S, 'G', 6); // it seems that this is a problem //
Printf ("% s", S );

Getchar ();
Return 0;
}
3. The memset () function is often used for memory space initialization. For example:
Char STR [100];
Memset (STR, 0,100 );

4. Deep connotation of memset (): it is used to set all memory space to a specific character. It is generally used to initialize the defined string to 'memset (A, '/0 ', sizeof ());

Memcpy is used for memory copying. You can use it to copy any data type object and specify the length of the copied data. For example, char a [100], B [50]; memcpy (B, a, sizeof (B); note that if sizeof (a) is used, the memory address of B may overflow.

Strcpy can only copy strings. It ends copying when '/0' is encountered. For example, char a [100], B [50]; strcpy (A, B ); if strcpy (B, A) is used, check whether the length of the string in A (before the first '/0') exceeds 50 bits. If it exceeds, this will cause memory address overflow of B.

5. Supplement: some of your experiences
Memset can easily clear a variable or array of the structure type.

For example:
Struct sample_struct
{
Char csname [16];
Int iseq;
Int itype;
};

For Variables
Struct sample_strcut sttest;

In general, the method of clearing sttest is as follows:
Sttest. csname [0] = '/0 ';
Sttest. iseq = 0;
Sttest. itype = 0;

Memset is very convenient:
Memset (& sttest, 0, sizeof (struct sample_struct ));

If it is an array:
Struct sample_struct test [10];
Then
Memset (test, 0, sizeof (struct sample_struct) * 10 );

6. Strcpy
Prototype: extern char * strcpy (char * DEST, char * SRC );
Usage: # I nclude
Function: Copies the string ending with null indicated by Src to the array indicated by DeST.
Note: The memory areas specified by Src and DEST cannot overlap and DEST must have sufficient space to accommodate SRC strings.
Returns the pointer to DeST.
Memcpy
Prototype: extern void * memcpy (void * DEST, void * SRC, unsigned int count );
Usage: # I nclude
Function: copy count bytes from the memory area indicated by Src to the memory area indicated by DeST.
Note: the memory areas specified by Src and DEST cannot overlap. The function returns a pointer to DeST.
Memset
Prototype: extern void * memset (void * buffer, int C, int count );
Usage: # I nclude
Function: sets the first count byte of the memory area referred to by buffer to character C.
Note: The pointer to the buffer is returned.

 

 

 

 

 

Usage of the memset function:

 

Set the value of the first n Bytes of memory space s to C

The following is an example.

# Include <stdio. h>
# Include <string. h>
Main (){
Char * s = "golden Global View ";

Clrscr ();

Memset (S, 'G', 6 );
Printf ("% s", S );

Getchar ();
Return 0;
}

The memset () function is often used for memory space initialization. For example:

Char STR [100];
Memset (STR, 0,100 );

 

Memset is used to set all memory spaces to a specific character. It is generally used to initialize the defined string to ''or '/0'. For example, char a [100]. memset (A, '/0', sizeof ());
Memcpy is used for memory copying. You can use it to copy any data type object and specify the length of the copied data. For example, char a [100], B [50]; memcpy (B, a, sizeof (B); note that if sizeof (a) is used, the memory address of B may overflow.

Strcpy can only copy strings. It ends copying when '/0' is encountered. For example, char a [100], B [50]; strcpy (A, B ); if strcpy (B, A) is used, check whether the length of the string in A (before the first '/0') exceeds 50 bits. If it exceeds, this will cause memory address overflow of B.

# Include <iostream>
# Include <cstring>
Using namespace STD;
Int main ()
{
Char A [5];
Memset (A, '1', 5 );
For (INT I = 0; I <5; I ++)
Cout <A [I] <"";
System ("pause ");
Return 0;
}
However, it is not feasible to set the element value in the array to 1 in the following program.
# Include <iostream>
# Include <cstring>
Using namespace STD;
Int main ()
{
Int A [5];
Memset (A,); // it cannot be changed to memset (A, * sizeof (INT) here.
For (INT I = 0; I <5; I ++)
Cout <A [I] <"";
System ("pause ");
Return 0;
}

Because the array a of the first program is of the bytes type, the memory occupied by the memory size is 1 byte, And the memset function is also assigned a value in bytes, so there is no problem with your output.
The second program A is an integer, and memset or byte value is used. After the value is assigned, the value of each array element is actually 0x01010101, that is, decimal 16843009.

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