use
char *itoa(int value，char *string，int radix)；
Header file:
Program example:
# include & ltstdlib.h & gt
# include & ltstdio.h & gt
int main()
{
Int number =123456;
char string[25]；
Itoa (number, string,10);
Printf("integer = %d string = %s\n ",number, string);
Returns 0;
}
/* Source code for implementing itoa function */
char *myitoa(int num，char *str，int radix)
{
/* Index table */
char index[]= " 0 123456789 abcdefghijklmnopqrstuvwxyz "；
Unsigned unum/* intermediate variable *
int i=0，j，k；
/* Determine the value of unum */
if(radix = = 10 & amp； & num<0)/* Decimal negative number */
{
Unum= (unsigned)-num;
str[i++]= '-'；
}
Else unum= (unsigned) num/* Other information */
/* Reverse order */
Do {
Str [i++] = index [unsigned% (unsigned) radix];
Unum/= radix;
} while(unum)；
str[I]= ' \ 0 '；
/* conversion */
if(str[0]= = '-')k = 1； /* Decimal negative number */
Otherwise k = 0；;
/* Change the original "/2" to "/2.0" to ensure that the correct result can be obtained when num is between 16~255 and radix is equal to 16 */
for(j = k； j & lt=(I- 1)/2.0+k； j++)
{
num = str[j]；
str[j]= str[I-j- 1+k]；
str[I-j- 1+k]= num；
}
Returns a string;
}
The third parameter of itoa is used to convert numbers into different decimal systems. For example:
# include & ltstdlib.h & gt
# include & ltstdio.h & gt
int main(void)
{
Int number =12345;
char string[25]；
Itoa (number, string,10); //Decimal conversion
Printf("integer = %d string = %s\n ",number, string);
Itoa (number, string,16); //Press 16 to convert.
Printf("integer = %d string = %s\n ",number, string);
Returns 0;
}
Output result:
Integer = 12345String = 12345-Description12345 is expressed in decimal as12345.
Integer =12345String = 3039-12345 is expressed in hexadecimal form of 0x3039.
However, it should be noted that itoa is not a standard C function, it is unique to Windows. If you want to write cross-platform programs, please use sprintf.
Let's use decimals:)
Examples of MSDN
example
/* ITOA。 C: This program converts various integers.
* String sizes of various radii.
*/
# include & ltstdlib.h & gt
# include & ltstdio.h & gt
Invalid master (invalid)
{
A charging buffer [20];
int i = 3445
Dragon l =-344115l;
Unsigned length ul =1234567890ul;
_itoa( i，buffer， 10)；
Printf ("string of integer %d (radix 10): %s\n", i, buffer);
_itoa( i，buffer， 16)；
Printf ("string of integer %d (radix 16): 0x%s\n", i, buffer);
_itoa( i，buffer，2)；
Printf ("string of integer %d (radix 2): %s\n", i, buffer);
_ltoa( l，buffer， 16)；
Printf (string of "long int% LD (radix16)": 0x%s\n ",l, buffer);
_ultoa( ul，buffer， 16)；
Printf ("unsigned long string %lu (radix 16): 0x%s\n", ul, buffer);
}
output
Integer string 3445 (radix 10): 3445
Integer string 3445 (radix 16): 0xd75
String of integer 3445 (radix 2):1111101
Long string -344 1 15 (radix 16):0x fffabbcd.
Unsigned long integer string 1234567890 (radix 16): 0x499602d2
Specifies the radix of the base to be converted, which seems to be between 1-36.
This is not a function in the C standard library, but an extension under the Windows platform. Sprintf is in the standard library, which is more powerful than this, and its usage is similar to printf:
char str[255]；
sprintf(str，" %x "， 100)； //Converts 100 into a string in hexadecimal notation.