Problems of global and local arrays in C language

Today, students encounter a global array in C language and local array problem, card for a long time, I do not see the first problem, now to comb the problem, and give a solution.

Problem Description:

An array that is declared globally has a different effect than a locally declared array.

First look at a program:

The code is as follows:

#include <stdio.h>

#include <stdlib.h>

#define MAX 10

Char A[max];

int main ()

{

int i;

Char B[max];

Char *c= (char *) malloc (MAX * sizeof (char));

printf ("Array A:");

for (i=0;i<max;i++)

printf ("%d", a[i]);

printf ("Array B:");

for (i=0;i<max;i++)

printf ("%d", b[i]);

printf ("Array C:");

for (i=0;i<max;i++)

printf ("%d", c[i]);

printf ("Done");

Free (c);

return 1;

}

Compile Run Results:

　　

The main function of the program is to print the ASCII code of the character array. You can see that global array A and dynamically generated array C have the same result, while the locally declared array B is indeed assigned a random number, perhaps that's where the problem lies.

Solution:

The code is as follows:

#include <stdio.h>

#include <stdlib.h>

#define MAX 10

Char a[max]={0};

int main ()

{

int i;

Char b[max]={0};

Char *c= (char *) malloc (MAX * sizeof (char));

printf ("Array A:");

for (i=0;i<max;i++)

printf ("%d", a[i]);

printf ("Array B:");

for (i=0;i<max;i++)

printf ("%d", b[i]);

printf ("Array C:");

for (i=0;i<max;i++)

printf ("%d", c[i]);

printf ("Done");

Free (c);

return 1;

}

Run Result:

　　

In the initialization of an array, assuming that the number of values initialized is less than the size of the array, all are populated with 0来. Here, by initializing a value, you can give the array a definite result.

(different results may occur in different systems and different compilers)

There is also a small problem is the C language of the problem, look at the following procedures.

The code is as follows:

#include <stdio.h>

#include <stdlib.h>

#define MAX 10

int main ()

{

int i;

Char b[max]={0};

Gets (b);

printf ("Array B:");

for (i=0;i<max;i++)

printf ("%d", b[i]);

printf ("Done");

return 1;

}

　　

Here, I entered "int" (three spaces +int) and printed the results as shown above.

The first three in B is a space-logged ASCII code, that is, 32.

The unused space in the back of B is still 0.