C program to Extract each byte into a character variable

[Parth86]

Hello
what is meaning of Extract each byte into a character variable (integer = hexadecimal value). does it means extract bytes from an integer (hexadecimal) value I don't understand logic behind to implement this program ?

 

[misterT]

Well, if you have 4-byte integer, you can extract the individual bytes and cast them to char-variable. There are many ways to do it.

int variable = 0x12345678; /* 4 byte integer containing some value */
char byte0, byte1, byte2, byte3; /* Variables to hold the char-values */

/* extract the bytes as characters */
byte0 = (char)((variable >> (0*8)) & 0x000000FF);
byte1 = (char)((variable >> (1*8)) & 0x000000FF);
byte2 = (char)((variable >> (2*8)) & 0x000000FF);
byte3 = (char)((variable >> (3*8)) & 0x000000FF);

/* Another way using pointers */
byte0 = ((char*)(&variable))[0];
byte1 = ((char*)(&variable))[1];
byte2 = ((char*)(&variable))[2];
byte3 = ((char*)(&variable))[3];

 

[Parth86]

Well, if you have 4-byte integer, you can extract the individual bytes and cast them to char-variable. There are many ways to do it.

int variable = 0x12345678; /* 4 byte integer containing some value */
char byte0, byte1, byte2, byte3; /* Variables to hold the char-values */

/* extract the bytes as characters */
byte0 = (char)((variable >> (0*8)) & 0x000000FF);
byte1 = (char)((variable >> (1*8)) & 0x000000FF);
byte2 = (char)((variable >> (2*8)) & 0x000000FF);
byte3 = (char)((variable >> (3*8)) & 0x000000FF);

/* Another way using pointers */
byte0 = ((char*)(&variable))[0];
byte1 = ((char*)(&variable))[1];
byte2 = ((char*)(&variable))[2];
byte3 = ((char*)(&variable))[3];

Thank you very much for your quick response I was reading this code. whats happening in program. why there is same value &0xFF in all statement

#include <stdio.h>

typedef unsigned char BYTE;

int main()
{
    unsigned int value=0x11223344; //4 Bytes value
     
    BYTE a,b,c,d; //to store byte by byte value
     
     
    a=(value&0xFF); //extract first byte
    b=((value>>8)&0xFF); //extract second byte
    c=((value>>16)&0xFF); //extract third byte
    d=((value>>24)&0xFF); //extract fourth byte

    printf("a= %02X\n",a);
    printf("b= %02X\n",b);
    printf("c= %02X\n",c);
    printf("d= %02X\n",d);
    return 0;
}

 

[misterT]

0x000000FF is a bit mask which is used to set all the upper bytes to zero "just in case". '&' is the bit-operator "AND".

byte0 = (char)(0x12345678 & 0x000000FF); /* The intermediate result of this is... */
byte0 = (char)(0x00000078); /* And after casting... */
byte0 = 0x78;

I think it is good habit to use the bit mask, but not necessary.