08.txt

一個計算機系教授的上課講義 主要是教導學生使用C語言編寫程序

CS 1355
Introduction to Programming in C
originally scheduled for Thursday 2006.10.5 (Week 4)
made-up on Thursday 2006.10.12 (Week 5)
Lecture notes (at http://r638-2.cs.nthu.edu.tw/C/notes/08.txt)

Chapter 4: C Program Control (cont'd)

- do-while loop
- break, continue
- logical operators

- do-while loop:
  - syntax
	do {
		statement....
	} while (condition); 
  - meaning:
    - enter the loop (statement...),
      execute the body statement AT LEAST ONCE!!
    - do the loop testing at the end of the loop:
      - if condition is true, then loop again
      - if condition is false, then exit loop 

Example: repeat from 1..10 (inclusively)

	int counter = 1;
	do {
		printf("%d ", counter);
	} while ( ++counter <= 10 );

Note:
- if you say (counter++ <= 10), then it goes from 1..9.
- if you say (++counter < 10), then it goes from 1..8.

Example: calculator, with an "accumulator"
Syntax:  
command number
------- ------
  +      number
  -      number
  *      number
  /      number
  c                   /* clear */
  q                   /* quit */

#include <stdio.h>
int main() {
        float accumulator = 0;
        float arg;
        int    command = 0;
        do {
                if (command != ' ') {
                        printf(">> "); /* print the prompt character */
                }
                command = getchar();
                switch (command) {
                case '+':
                        if (scanf("%f", &arg) == 1) {
                                accumulator += arg;
                                printf("%f\n", accumulator);
                        } else { /* failed to get a number */
                                command = 'q';
                        }
                        break; /* 铬