Quick Introduction to C

Simple program

• program text

  		#include <stdio.h>
  
  		int
  		main(void)
  		{
  		  printf("hello, world\n");
  		  return 0;
  		}
  

• #include <stdio.h>
  • includes (among other things) a definition of the printf() function used in this program
• int main(void)
  • C function declaration
    • every routine in C is a function that is passed a list of 0 or more arguments
    • is possible to declare a function that doesn't return anything (i.e. a subroutine)
  • first part of any C declaration is the datatype
    • in this case, the function returns an integer, written in C as int
  • second part of function declaration is function name
    • in this case, the function is named main
    • every C program begins execution with the main() function
    • main() function ALWAYS returns an integer
  • third part of function declaration is list of arguments
    • always enclosed in parentheses
    • in this case, we've specified "void" to indicate that there are no arguments
• { ... }
  • block of C code enclosed in "braces" or "curly brackets"
  • body of function must ALWAYS be enclosed in braces
• printf("hello, world\n")
  • call to function named printf
  • as before, list of arguments is enclosed in parentheses
  • in this case, argument is a character string, "hello, world\n"
    • \n is a special character escape sequence
    • \ means treat the next character in a special way
    • \n together is interpreted to mean restart output on the next line down
  • ; is the end-of-statement indicator
• return 0;
  • return sets the return value for a function and exits the function