memcpy() in C

The memcpy() function in C is used to copy a block of memory from a source location to a destination location. It is part of the C Standard Library and is often used for copying data from one data structure to another, such as arrays, strings, or structs. The function has the following prototype:

void *memcpy(void *dest, const void *src, size_t n);

• dest: A pointer to the destination memory location where the data will be copied.
• src: A pointer to the source memory location from which the data will be copied.
• n: The number of bytes to copy.

Here’s an example of how to use memcpy():

#include <stdio.h>
#include <string.h>

int main() {
    char source[] = "Hello, World!";
    char destination[20];

    // Copy the contents of 'source' to 'destination'
    memcpy(destination, source, strlen(source) + 1);

    printf("Source: %s\n", source);
    printf("Destination: %s\n", destination);

    return 0;
}

In this example:

1. We have a source string source containing the text “Hello, World!” and a destination character array destination.
2. We use memcpy() to copy the contents of source to destination. We specify the length of the source string using strlen(source) + 1 to ensure that the null-terminator (‘\0’) is also copied.
3. After copying, both source and destination contain the same text.

Important points to note about memcpy():

• It copies data byte by byte, so it is suitable for copying binary data as well as text.
• It doesn’t perform any type checking, so it treats the memory as an array of bytes.
• It’s important to ensure that the destination buffer has enough space to accommodate the copied data to avoid buffer overflow.
• It’s a low-level memory operation and doesn’t handle memory allocation or resizing.
• The memcpy() function returns a pointer to the destination, but this is typically not used since it is the same as the dest argument.

For safer string and memory operations, especially when working with strings, you may prefer to use functions like strcpy() for strings and dynamic memory allocation functions such as malloc() and free().