What does %d

What does %d mean? [closed]

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I'm reading a C program, and I have a question that I think may be related to type casting. Basically, the program will follow. I've commented in a few questions that pasted over from my clipboard. Don't worry about those so much as the question that immediately follows the code block. /* I only need the out in in/out, right?  Or do I need in and out? */ #include<stdio.h> /* can someone explain the second argument?  A char is only supposed to be one character so howcome it has square brackets after it, which indicate an array to me?  Also, what's with the asterisk? */

int main(int argc,char *argv[]) {   int i; /* Here %d is used, which I'm thinking might mean double */   printf("Amount: %d\n",argc);   if (argc > 0)   {     printf("Parameters:\n");     for (i = 0;i < argc;i++) /* Here %s is used, which I'm thinking might mean string */       printf("%s\n",argv[i]);   }   return 0; } I'm not sure what the group of %-identified items is called, so I'm not sure where to find a reference of their meanings down voteaccepted question 1) the header file <stdio.h> is included in order to have reference to the input/output function from C library. The <stdio.h> contains only function references and not the definition of the functions. The <stdio.h> contains references to functions like: ·         printf (out) output to stdout (default: screen) ·         scanf (in) reading from stdin (default: keyboard) question 2) char *argv[] is an array of pointer. Each pointer element is pointing to a string. Each string is an argument from the command line. Example: If your program name after compilation is "myprogram" and you calling your program as following: $myprogram -t test1 test2 So the argv is an array containing 4 pointers to the following string argv[0] is a pointer to the string "myprogram" argv[1] is a pointer to the string "-t" argv[2] is a pointer to the string "test1" argv[3] is a pointer to the string "test2" question 3) %d means integer and not double. For double you can use %lf or %g question 4) %s means that you are printing string example related to argv: printf("argv[0] = %s\n", argv[0]); printf("argv[1] = %s\n", argv[1]); printf("argv[2] = %s\n", argv[2]); printf("argv[3] = %s\n", argv[3]); based on question 2 the above prints give the following output: argv[0] = myprogram argv[1] = -t argv[2] = test1 argv[3] = test2