Variables and Arithmetic Expression

标签：

Notes from The C Programming Language

A decimal point in a constant indicates that it is floating point, however, so $5.0/9.0$ i not truncated because it is the ratio of two floating-point values.

printf specification

• %3.0f says that a floating-point number is to be printed at least three characters wide, with no decimal point and no fraction dgits.
• %6.1f describes another number that is to be printed at least six characters wide, with 1 digit after the decimal point.

Width and precision may be omitted from a specification: %6f says that the number is to be at least six characters wide; %.2f specifies two characters after the decimal point, but the width is not constrained.

• %o for octal
• %x for hexadecimal
• %c for character
• %s for character string
• %% for % itself

for statement:

#include <stdio.h>

#define LOWER 0			/* lower limit of table */
#define UPPER 300		/* upper limit */
#define STEP  20		/* step size */

/* print Fahrenheit-Celsius table */
main()
{
	int fahr;
	
	for(fahr = LOWER; fahr <= UPPER; fahr = fahr + STEP)
		printf("%3d %6.1f\n", fahr, (5.0/9.0)*(fahr-32));
}

Character input and output

The standard library provides getchar() and putchar() for reading and writing one character at a time. getchar() reads the next input character from a text stream and returns that as its value:

c = getchar();

The function putchar prints a character each time:

putchar(c);

prints the contents of the integer variable c as a character, usually on the screen.

File copy: a program that copies its input to its output one character at a time:

#include <stdio.h>

/* copy input to output; 1st version */
main()
{
	int c;
	
	c = getchar();
	while(c != EOF)
	{
		putchar(c);
		c = getchar();
	}
}

EOF is defined in <stdio.h>.

As an expression has a value, which is the left hand side after the assignment, the code can be concise:

#include <stdio.h>

/* copy input to output; 2nd version */
main()
{
	int c;
	
	while((c = getchar()) != EOF)
		putchar(c);
}

Variables and Arithmetic Expression

标签：

原文地址：http://www.cnblogs.com/kid551/p/4268623.html