Question

你好我对c ++变量类型（char）有一些疑问我在一些网站上读到这个字符支持范围从（-128到127）和无符号（0到255）。这是什么意思？

char支持的不仅仅是数字，为什么他们说（-128到127）？

这个范围是什么意思？

什么范围？

我的另一个问题是：什么时候可以使用这个

    --2017-02-13 18:04:46--  http://chromedriver.storage.googleapis.com/2.21/chromedriver_linux64.zip
    Resolving chromedriver.storage.googleapis.com (chromedriver.storage.googleapis.com)... 64.233.191.128, 2607:f8b0:4001:c0c::80
    Connecting to chromedriver.storage.googleapis.com (chromedriver.storage.googleapis.com)|64.233.191.128|:80... connected.
    HTTP request sent, awaiting response... 200 OK
    Length: 2692616 (2.6M) [application/zip]
    Saving to: `chromedriver_linux64.zip'
     0% [                                       ] 0           --.-K/s                100%[======================================>] 2,692,616   --.-K/s   in 0.009s  



    wget: unable to resolve host address `.'
    FINISHED --2017-02-13 18:04:48--
    Total wall clock time: 1.5s
    Downloaded: 1 files, 2.6M in 0.009s (281 MB/s)
    The command "wget http://chromedriver.storage.googleapis.com/2.21/chromedriver_linux64.zip - unzip chromedriver_linux64.zip - sudo chmod u+x chromedriver - sudo mv chromedriver /usr/bin/ - export CHROME_BIN=chromium-browser - "export DISPLAY=:99.0" - "sh -e /etc/init.d/xvfb start" - sleep 3 - ./travis_before_install" failed and exited with 4 during .
    Your build has been stopped.


Also, Could someone please let me know, why travis wouldnt run this?

`The command "bundle exec cucumber" exited with 2.`


UPDATE: I updated the file fixing the indentation in the `before_script` . The latest error i get is 

    0.08s$ unzip chromedriver_linux64.zip
   Archive:  chromedriver_linux64.zip
  inflating: chromedriver            
   before_script.10
   0.01s$ sudo chmod u+x chromedriver
   before_script.11
   0.01s$ sudo mv chromedriver /usr/bin/
   before_script.12
   0.00s$ export CHROME_BIN=chromium-browser
   before_script.13
   0.00s$ export DISPLAY=:99.0
   before_script.14
   0.01s$ sh -e /etc/init.d/xvfb start
   Starting virtual X frame buffer: Xvfb.
   before_script.15
   3.01s$ sleep 3
   2.55s$ bundle exec cucumber
   end of file reached (EOFError)
   The command "bundle exec cucumber" exited with 2.
Done. Your build exited with 1. 


     **Update:** I tried fixing up the identation errors in the script as. The new error i get is 

     0% [                                       ] 0           --.-K/s                  100%[======================================>] 2,692,616   --.-K/s   in 0.01s   
   2017-02-14 11:00:45 (173 MB/s) - ‘chromedriver_linux64.zip’ saved    [2692616/2692616]
    before_script.9
   0.08s$ unzip chromedriver_linux64.zip
   Archive:  chromedriver_linux64.zip
   inflating: chromedriver            
    before_script.10
   0.01s$ sudo chmod u+x chromedriver
   before_script.11
   0.01s$ sudo mv chromedriver /usr/bin/
   before_script.12
   0.00s$ export CHROME_BIN=chromium-browser
   before_script.13
   0.00s$ export DISPLAY=:99.0
   before_script.14
   0.01s$ sh -e /etc/init.d/xvfb start
   Starting virtual X frame buffer: Xvfb.
   before_script.15
   3.01s$ sleep 3
   2.55s$ bundle exec cucumber
   **end of file reached (EOFError)**
   The command "bundle exec cucumber" exited with 2.
    Done. Your build exited with 1.

为什么我们需要在char之前设置unsigned或signed或...？

使用此操作（也使用const char * Data; Data = "dddddddddddddddddddddddddddddddddddddddddddddddde21312313dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddde21312313dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddde21312313dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddde21312313dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddde21312313dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd";）系统自动检测char的长度并保持正常和标准大小的存储大小...为什么我们需要设置*的大小这个并具有动态大小并跳过静态大小？

或者这个动作为什么我们需要（(char Data[255])）了？！

Answer 1

char支持不只是数字，为什么他们说（-128到127）？

实际上，你错了。 char s 只是数字。您正在考虑这些数字的ASCII表示。例如，您看到的d实际上是数字100。

因此，可以说签名char可以容纳的唯一值在-128→127范围内。但是，该语句假定没有限定符的char已签名，并非总是如此。

C ++ char类型的长度和大小

1 个答案: