%i or %d - where is the difference?

Question: Where is the difference between %i and %d that are used in e.g. printf(), fscanf() and so on ? When do I have to use %i instead of %d and vice versa?
Although I do have the C99 Language Standard I don't know what is meant in the description of %i and %d.

Thank you for your help.

%d Matches an optionally signed decimal integer, whose format is the same as
expected for the subject sequence of the strtol function with the value 10
for the base argument. The corresponding argument shall be a pointer to
signed integer.
%i Matches an optionally signed integer, whose format is the same as expected
for the subject sequence of the strtol function with the value 0 for the
base argument. The corresponding argument shall be a pointer to signed
integer.

7.20.1.4 The strtol, strtoll, strtoul, and strtoull functions
Synopsis
1 #include <stdlib.h>
long int strtol(
const char * restrict nptr,
char ** restrict endptr,
int base);
long long int strtoll(
const char * restrict nptr,
char ** restrict endptr,
int base);
unsigned long int strtoul(
const char * restrict nptr,
char ** restrict endptr,
int base);
unsigned long long int strtoull(
const char * restrict nptr,
char ** restrict endptr,
int base);
Description
2 The strtol, strtoll, strtoul, and strtoull functions convert the initial
portion of the string pointed to by nptr to long int, long long int, unsigned
long int, and unsigned long long int representation, respectively. First,
they decompose the input string into three parts: an initial, possibly empty, sequence of
white-space characters (as specified by the isspace function), a subject sequence
resembling an integer represented in some radix determined by the value of base, and a
251) DECIMAL_DIG, defined in <float.h>, should be sufficiently large that L and U will usually round
to the same internal floating value, but if not will round to adjacent values.
§7.20.1.4 Library 309
ISO/IEC 9899:1999 (E) ©ISO/IEC
final string of one or more unrecognized characters, including the terminating null
character of the input string. Then, they attempt to convert the subject sequence to an
integer, and return the result.
3 If the value of base is zero, the expected form of the subject sequence is that of an
integer constant as described in 6.4.4.1, optionally preceded by a plus or minus sign, but
not including an integer suffix. If the value of base is between 2 and 36 (inclusive), the
expected form of the subject sequence is a sequence of letters and digits representing an
integer with the radix specified by base, optionally preceded by a plus or minus sign,
but not including an integer suffix. The letters from a (or A) through z (or Z) are
ascribed the values 10 through 35; only letters and digits whose ascribed values are less
than that of base are permitted. If the value of base is 16, the characters 0x or 0X may
optionally precede the sequence of letters and digits, following the sign if present.
4 The subject sequence is defined as the longest initial subsequence of the input string,
starting with the first non-white-space character, that is of the expected form. The subject
sequence contains no characters if the input string is empty or consists entirely of white
space, or if the first non-white-space character is other than a sign or a permissible letter
or digit.
5 If the subject sequence has the expected form and the value of base is zero, the sequence
of characters starting with the first digit is interpreted as an integer constant according to
the rules of 6.4.4.1. If the subject sequence has the expected form and the value of base
is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
as given above. If the subject sequence begins with a minus sign, the value resulting from
the conversion is negated (in the return type). A pointer to the final string is stored in the
object pointed to by endptr, provided that endptr is not a null pointer.
6 In other than the "C" locale, additional locale-specific subject sequence forms may be
accepted.
7 If the subject sequence is empty or does not have the expected form, no conversion is
performed; the value of nptr is stored in the object pointed to by endptr, provided
that endptr is not a null pointer.
Returns
8 The strtol, strtoll, strtoul, and strtoull functions return the converted
value, if any. If no conversion could be performed, zero is returned. If the correct value
is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
and sign of the value, if any), and the value of the macro ERANGE is stored in errno.

When using %i to print an integer its same as %d..
But when used with scanf i -reads an optionall signed decimal,octal,hex ...

An e.g

Code:

   int num1, num2;
    
   printf("Enter 2 numbers: " );
   scanf( "%d%i", &num1, &num2 );

   printf("Inputs diaplayed in decimal integer: %d %d", num1,      num2 );

Enter 070 for both for num1 the it will display num1 as 70 and num2 as 56 .....

56 is the octal equallent of 070

That's good to know! Thank you very much.

56 is the octal equallent of 070 [/B]

Don't you mean "56 is the decimal equivalent of the octal 070"?

Originally posted by Sargnagel
That's good to know! Thank you very much.


Don't you mean "56 is the decimal equivalent of the octal 070"?

YEah sorry about that