CSC373/406: C: Formatting [32/42]

file:hello.c [source]

00001: #include <stdio.h> 00002: 00003: int main() 00004: { 00005: printf("hello, world\n"); 00006: } 00007:

• #include is a preprocessor directive: it literally includes other code into your program (prototypes for constants, functions, etc.), which then gets compiled as though it were part of what you wrote
• Your program must contain a function called main
• Elementary i/o in C is performed by 2 functions: scanf for input, and printf for output
• Both take format strings which specify the data types to read (or a combination of data types plus text to print)
  • Composed of ordinary characters (not %)
    • Copied unchanged into the output
  • Conversion specifications (start with %)
    • Fetches one or more arguments

      char    %c
      char[]  %s  // string
      int     %d  // signed decimal (base 10)
      int     %u  // unsigned decimal (base 10)
      int     %x  // unsigned hexidecimal (base 16)
      int     %p  // pointer (like %x but with leading 0x)
      float   %f
      

• There really should be a return statement at the end of the program: return 0;

file:format.c [source]

00001: #include <stdio.h> 00002: 00003: int main() 00004: { 00005: printf ("Characters: %c %c \n", 'a', 65); 00006: printf ("Characters: %d %d \n", 'a', 65); 00007: printf ("Decimals: %d %d\n", 1977, 65000000); 00008: printf ("Preceding with blanks: %10d \n", 1977); 00009: printf ("Preceding with zeros: %010d \n", 1977); 00010: printf ("Some different radixes: %d %x %o %#x %#o \n", 00011: 100, 100, 100, 100, 100); 00012: printf ("floats: %4.2f %+.0e %E \n", 3.1416, 3.1416, 3.1416); 00013: printf ("%s \n", "A string"); 00014: int x; 00015: float y; 00016: printf("Enter a decimal and a floating point number\n"); 00017: scanf("%d %f", &x, &y); 00018: printf("You entered %d %lf\n", x, y); 00019: 00020: char s[1]; 00021: printf("Enter a string\n"); 00022: scanf("%s", s); 00023: printf("You entered %s\n", s); 00024: return 0; 00025: } 00026: