C++编程思想 第1卷 第3章 for语句

第一次循环，for的变量初始化
测试条件决定是否执行循环

每一次循环结束循环变量会变化

//: C03:Charlist.cpp
// From Thinking in C++, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 2000
// Copyright notice in Copyright.txt
// Display all the ASCII characters
// Demonstrates "for"
#include <iostream>
using namespace std;

int main() {
  for(int i = 0; i < 128; i = i + 1)
    if (i != 26)  // ANSI Terminal Clear screen
      cout << " value: " << i 
           << " character: " 
           << char(i) // Type conversion
           << endl;
  getchar();
} ///:~

变量i在使用他的地方定义。而不是在程序块起始处定义
和传统C语言形成对照，C语言要在程序块起始处定义


输出
 value: 0 character:
 value: 1 character:
 value: 2 character:
 value: 3 character:
 value: 4 character:
 value: 5 character:
 value: 6 character:
 value: 7 character:
 value: 8 character:
 value: 9 character:
 value: 10 character:


 value: 11 character:
 value: 12 character:
 value: 13 character:
 value: 14 character:
 value: 15 character:
 value: 16 character:
 value: 17 character:
 value: 18 character:
 value: 19 character:
 value: 20 character:
 value: 21 character:
 value: 22 character:
 value: 23 character:
 value: 24 character:
 value: 25 character:
 value: 27 character:
 value: 28 character:
 value: 29 character:
 value: 30 character:
 value: 31 character:
 value: 32 character:
 value: 33 character: !
 value: 34 character: "
 value: 35 character: #
 value: 36 character: $
 value: 37 character: %
 value: 38 character: &
 value: 39 character: '
 value: 40 character: (
 value: 41 character: )
 value: 42 character: *
 value: 43 character: +
 value: 44 character: ,
 value: 45 character: -
 value: 46 character: .
 value: 47 character: /
 value: 48 character: 0
 value: 49 character: 1
 value: 50 character: 2
 value: 51 character: 3
 value: 52 character: 4
 value: 53 character: 5
 value: 54 character: 6
 value: 55 character: 7
 value: 56 character: 8
 value: 57 character: 9
 value: 58 character: :
 value: 59 character: ;
 value: 60 character: <
 value: 61 character: =
 value: 62 character: >
 value: 63 character: ?
 value: 64 character: @
 value: 65 character: A
 value: 66 character: B
 value: 67 character: C
 value: 68 character: D
 value: 69 character: E
 value: 70 character: F
 value: 71 character: G
 value: 72 character: H
 value: 73 character: I
 value: 74 character: J
 value: 75 character: K
 value: 76 character: L
 value: 77 character: M
 value: 78 character: N
 value: 79 character: O
 value: 80 character: P
 value: 81 character: Q
 value: 82 character: R
 value: 83 character: S
 value: 84 character: T
 value: 85 character: U
 value: 86 character: V
 value: 87 character: W
 value: 88 character: X
 value: 89 character: Y
 value: 90 character: Z
 value: 91 character: [
 value: 92 character: \
 value: 93 character: ]
 value: 94 character: ^
 value: 95 character: _
 value: 96 character: `
 value: 97 character: a
 value: 98 character: b
 value: 99 character: c
 value: 100 character: d
 value: 101 character: e
 value: 102 character: f
 value: 103 character: g
 value: 104 character: h
 value: 105 character: i
 value: 106 character: j
 value: 107 character: k
 value: 108 character: l
 value: 109 character: m
 value: 110 character: n
 value: 111 character: o
 value: 112 character: p
 value: 113 character: q
 value: 114 character: r
 value: 115 character: s
 value: 116 character: t
 value: 117 character: u
 value: 118 character: v
 value: 119 character: w
 value: 120 character: x
 value: 121 character: y
 value: 122 character: z
 value: 123 character: {
 value: 124 character: |
 value: 125 character: }
 value: 126 character: ~
 value: 127 character: