编译时错误C编程数组

Question

I wrote a small C program which takes some user input and prints it,

#include<stdio.h>
int main()
{
    char name[], char add[];
    short int height;
    unsigned char buffer[1024];
    int i,j,n,m;

    printf("enter your name_length num: n is:-\n");
    scanf("%d",&n);

    printf("enter your name\n");

    for(i=0;i<n;i++)
    {
        scanf("%c",&name[i]);
    }

    printf("enter your address: m is :-\n");
    scanf("%d",&m);

    for(j=0;j<n;j++)
    {
        scanf("%c",&add[j]);
    }

    printf("enter your height\n");
    scanf("%d",&height);


    for(i=0;i<n;i++)
    {
        printf("your entered name is:\t",name[i]);
    }

    for(j=0;j<n;j++)
    {
        printf("your entered address is:\t",add[i]);
    }

    printf("your entered height is:\n",height);

 return;
}

but while running I am getting an error -

So I am at my wits end on why the array size missing is coming, is there anything that I have missed ???

Answer 1

There are few problems in declaration syntax. Change this line

from

char name[], char add[];

to

char name[256],  add[256];

After this you get run-time errors ( welcome to C programming )

Answer 2

In C you must declare array with a constant integer like,

char name[1000],  add[1000];

OR

char name[1000];
char add[1000];

OR

int size=1000;
char name[size];
char add[size];

And your main function should return integer at the end, use

return 0;

Answer 3

As others have pointed out, the line char name[], char add[]; is invalid. This is because there is no way of knowing how much memory to assign to the array. There are two solutions, depending on your problem.

The best solution in this instance would be to move the declaration to below where you know the length of the user's name (assuming you're not using a strict format requiring declarations at the top):

printf("enter your name_length num: n is:-\n");
scanf("%d",&n);
char name[n];

This creates a fixed length array (of length n ), and given a user's name isn't likely to change length over the course of this program this is more than acceptable.

The alternate solution is to use memory allocation, which allows you to increase or decrease the size of the array during runtime.

char *name = null;
...
printf("enter your name_length num: n is:-\n");
scanf("%d",&n);
name = malloc( n * sizeof(char));

This assigns n * sizeof(char) bytes to the array, which can later be extended, reassigned or freed. This is the more flexible option.