About char str[20]= "" and char str[20]=““

As the title , Define a length of 20 String , The difference is that there is nothing in a double quotation mark , There is a space in the other double quotation mark . In order to know what the string stored in the array is , We use the debugging function , see str What is in the array .

This is a str[20]=""

This is a str[20]=" "

So that we can know , When we drive 20 Byte character array , And when there are not enough characters , It will automatically add '\0', So we can see , One only repeats 19 Time , One only repeats 18 Time , that '\000' What is it ？

According to the Internet ：\000 yes \0 Three digit octal

Let's do another example , We can use double quotation marks as an array of spaces , The second element is changed to e , At this time, the number of repetitions is determined by 18 Turned into 17, And the final output , It's exactly what we want （puts The output defaults to one line , no need \n）

The same way , We use it on arrays that have nothing in double quotes , Find that the situation is not the result we expected

What's the reason for this ？

The possible reason is , According to what we just said ,\000, May be \0 The effect of , When we change the second element , The first is still \000, So the string is equivalent to the end , The final output is naturally a blank

  When we modify the first element , It turned out that it was modified

When we modify both the first and the second , Find out , The output is as we expected  

summary ：str[20]="" and str[20]=" ", In fact, there is no big difference , It's usually out of the same imagination as a number array , Initialize the array to 0, Then use circulation and other means , Modify its value . Since its size was defined at the beginning as 20, When the total bytes modified later are insufficient 20 When , The remaining bytes ( It's not used ) No output , This is its advantage .