• 1 output

#include <stdio.h>

int main()
{
    printf("Hello, world!\n");
    return 0;
}

#include <stdio.h>

int main()
{
    printf("Hello, ");
    printf("world!\n");
    return 0;
}

這兩個程序的輸出結(jié)果一樣：

Hello, world!

Each time printf() is called, printing begins at the position where the previous call to printf() left off.

• 2 symbolic constants

#define PI 3.14159

• 3 field width

    printf("%c%3c%5c\n", 'A', 'B', 'C');

結(jié)果：

A  B    C

The field width can be specified in a format as an integer occurring between the % and the conversion character.

• 4 input

  scanf("%d", &x);

The format %d is matched with the expression &x, causing scanf() to interpret characters in the input stream as a decimal integer and to store the result at the address of x.

• 5 ++/--

    int a, b, c=0, d=0;
    a=++c;
    b=d++;
    printf("a=%d, b=%d\n", a, b);

結(jié)果：

a=1, b=0

• 6 typedef

//stdint.h
typedef int         int32_t;

• 7 EOF

//stdio.h
/* End of file character.
   Some things throughout the library rely on this being -1.  */
#ifndef EOF
# define EOF (-1)
#endif

• 8 continue v.s. break

    for(int i=1; i<10; ++i)
    {
        if(i%3==0)
            continue;
        printf("%d\t", i);
    }

結(jié)果：

1   2   4   5   7   8   

The continue statement causes the current iteration of a loop to stop and causes the next iteration of the loop to begin immediately.

    for(int i=1; i<10; ++i)
    {
        if(i%3==0)
            break;
        printf("%d\t", i);
    }

結(jié)果：

1   2   

The break statement causes an exit from the intermost enclosing loop or switch statement.

• 9 condition operator

x = (y<z) ? y : z

等價于

if(y<z)
  x=y
else
  x=z

• 10 switch

    char c='a';

    switch(c)
    {
        case 'a':
            printf("apple\n");
            break;
        case 'b':
            printf("banana\n");
            break;
        case 'c':
            printf("cat\n");
            break;
        case 'd':
            printf("dog\n");
            break;
        default:
            printf("other\n");
    }

結(jié)果：

apple