What does %s and %d mean in printf in the C language? [closed]

Answer 1

"%s%d%s%d\n" is the format string; it tells the printf function how to format and display the output. Anything in the format string that doesn't have a % immediately in front of it is displayed as is.

%s and %d are conversion specifiers; they tell printf how to interpret the remaining arguments. %s tells printf that the corresponding argument is to be treated as a string (in C terms, a 0-terminated sequence of char); the type of the corresponding argument must be char *. %d tells printf that the corresponding argument is to be treated as an integer value; the type of the corresponding argument must be int. Since you're coming from a Java background, it's important to note that printf (like other variadic functions) is relying on you to tell it what the types of the remaining arguments are. If the format string were "%d%s%d%s\n", printf would attempt to treat "Length of string" as an integer value and i as a string, with tragic results.

Answer 2

%s is for string %d is for decimal (or int) %c is for character

It appears to be chewing through an array of characters, and printing out whatever string exists starting at each subsequent position. The strings will stop at the first null in each case.

The commas are just separating the arguments to a function that takes a variable number of args; this number corresponds to the number of % args in the format descriptor at the front.

Answer 3

The printf() family of functions uses % character as a placeholder. When a % is encountered, printf reads the characters following the % to determine what to do:

%s - Take the next argument and print it as a string
%d - Take the next argument and print it as an int

See this Wikipedia article for a nice picture: printf format string

The \n at the end of the string is for a newline/carriage-return character.