hwo to define a char array with null value and how to check?

for exmaple:

Code:

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char buff[6][35];

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how to set the whoe array has no value at the beginning and how to if it has and charater inside??
use the function strcmp()??

thank you for helping.

Code:

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#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cstring>

int main()
{
    int i,j;
    char buff[5][3]={0};  // this initializes the whole thing to 0 (null)

    for (i=0;i<5;i++)
        for(j=0;j<2;j++)
            if(buff[i][j])
                printf("found %c\n", buff[i][j]);
                else printf("nothing here\n");

    strcpy(buff[2],"ab");

    for (i=0;i<5;i++)
        for(j=0;j<2;j++)
            if(buff[i][j])
                printf("found %c\n", buff[i][j]);
                else printf("nothing here\n");


    system("PAUSE");
    return 0;
}

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