What is the default value of an element of an uninitialized character array?

Question

here's a code I wrote

    int main(){
    char arr[50][*];
    arr[0][0]=1;
    if(arr[0][1]){
    printf("%d",arr[0][0]);}

If I am putting 1 as *, there is no output. but anything greater than 1 in the array size would result in 1 output.that means when I am declaring array size the elements are occupied by some value.

now, my actual need is to write a condition if loop (example)

if(arr[0][1]!='null') // or '0',false,undefined, etc

but I am confused what is there in that empty but declared element, because the above is not working.

you have not initialized the arr, so cannot say what gets printed — csavvy
– csavvy, Commented Nov 12, 2020 at 4:33

Keith Thompson · Accepted Answer · 2020-11-12 04:34:27Z

4

There is no default value.

For an object defined inside a function without the static keyword, the initial value is garbage.

You can't test an object to determine whether it's been initialized or not. You have to write your code to avoid reading any object's value before it's been set.

answered Nov 12, 2020 at 4:34

Keith Thompson

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3 Comments

mr.loop Over a year ago

actually I was trying to print an array whose size I don't know

Keith Thompson Over a year ago

@mr.loop The code in your question doesn't show an array whose size you don't know. I can only answer the question you asked.

mr.loop Over a year ago

let me rephrase that. I wanted to print an array whose number of initialized or defined elements I don't know. anyways, i got the answer.

mr.loop · Accepted Answer · 2020-11-12 06:06:58Z

1

doing(while declaring),

char arr[50][2]={0}  //or whatever the size of 2nd dimension other than 2

this will replace all elements(100 in this case) with 0.

So, according to my necessity,I can do

if(arr[0][1] != 0)

for checking if that element is undefined by me. this example works when your input doesn't contain 0, if it does replcae all elements with something else and also the condition too

answered Nov 12, 2020 at 6:06

mr.loop

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