i or d to print integer in C using printf

Question

I am just learning C and I have a little knowledge of Objective-C due to dabbling in iOS development  however  in Objective-C I was using NSLog    i   x   to print the variable x to the console however I have been reading a few C tutorials and they are saying to use  d instead of  i   printf   d   x   and printf   i   x   both print x to the console correctly    These both seem to get me to the same place so I am asking the experienced developers which is preferred  Is one more semantically correct or is right

User · Answer

As others said  they produce identical output on printf  but behave differently on scanf   I would prefer  d over  i for this reason   A number that is printed with  d can be read in with  d and you will get the same number   That is not always true with  i  if you ever choose to use zero padding   Because it is common to copy printf format strings into scanf format strings  I would avoid  i  since it could give you a surprising bug introduction   I write fprintf   i              You copy and write fscanf  i              I decide I want to align columns more nicely and make alphabetization behave the same as sorting   fprintf   03i              or  04d   Now when you read my numbers  anything between 10 and 99 is interpreted in octal   Oops   If you want decimal formatting  just say so

User · Answer

They are completely equivalent when used with printf    Personally  I prefer  d  it s used more often  should I say  it s the idiomatic conversion specifier for int       One difference between  i and  d is that when used with scanf    then  d always expects a decimal integer  whereas  i recognizes the 0 and 0x prefixes as octal and hexadecimal  but no sane programmer uses scanf   anyway so this should not be a concern

User · Answer

d and i conversion specifiers behave the same with fprintf but behave differently for fscanf   As some other wrote in their answer  the idiomatic way to print an int is using d conversion specifier    Regarding i specifier and fprintf  C99 Rationale says that      The  i conversion specifier was added in C89 for programmer convenience to provide    symmetry with fscanf   s  i conversion specifier  even though it has exactly the same meaning    as the  d conversion specifier when used with fprintf

User · Answer

both  d and  i can be used to print an integer    d stands for  decimal   and  i for  integer   You can use  x to print in hexadecimal  and  o to print in octal   You can use  i as a synonym for  d  if you prefer to indicate  integer  instead of  decimal    On input  using scanf    you can use use both  i and  d as well   i means parse it as an integer in any base  octal  hexadecimal  or decimal  as indicated by a 0 or 0x prefix   while  d means parse it as a decimal integer     check here for more explanation  why does  d stand for Integer

User · Answer

d seems to be the norm for printing integers  I never figured out why  they behave identically

User · Answer

I am just adding example here because I think examples make it easier to understand   In printf   they behave identically so you can use any either  d or  i  But they behave differently in scanf     For example   int main         int num num2      scanf   d i   amp num  amp num2     reading num using  d and num2 using  i      printf   d t d  num num2       return 0      Output     You can see the different results for identical inputs    num   We are reading num using  d so when we enter 010 it ignores the first 0 and treats it as decimal 10    num2   We are reading num2 using  i   That means it will treat decimals  octals  and hexadecimals differently   When it give num2 010 it sees the leading 0 and parses it as octal   When we print it using  d it prints the decimal equivalent of octal 010 which is 8

[c] %i or %d to print integer in C using printf()?

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