Why my code is printing an heart at printf? - c

Question

This is my code:
#include<stdio.h>
#include<stdlib.h>
main(){
char *alf="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!##$%&.",text[64];
int i, alfl=69;
srand(time(0));
for(i=0;i<64;i++)
text[i] = *(alf+rand()%alfl);
printf("%s",text);
}
But at the printf function it print an heart at final of the string.

Answer 1

As others have suggested in the comments (#mbratch and #KerrekSB) you need a null terminator at the end of your string.
Modify your code as follows:
#include<stdio.h>
#include<stdlib.h>
main(){
char *alf="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!##$%&.",text[64];
int i, alfl=69;
srand(time(0));
for(i=0;i<63;i++)
text[i] = *(alf+rand()%alfl);
text[i] = '\0';
printf("%s",text);
}
And it should work, but as #Simon suggested there can be other things that could help improve your code and understanding of C.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define LEN 64
int main() { // If you don't add a return type, int is assumed. Please specify it as void or int.
const char *alf="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!##$%&."; // This string cant be assigned to. Make sure that you stay "const-correct".
char text[LEN]; // Please avoid magic numbers here too by using a constant
int i, alfl = strlen(alf); // As #Simon says, it is better to not use magic constants.
srand(time(0));
for(i=0;i<LEN-1;i++)
text[i] = *(alf+rand()%alfl);
text[i] = '\0'; // make sure to null terminate your string.
printf("%s",text);
return 0; // If your return type is int, you must return from the function.
}

Answer 2

Several suggestions:
main should return an int:
int main(void)
{
return 0;
}
You should use strlen to determine the length of strings:
alfl = strlen(alf);
It's easier to use array notation:
for(i = 0; i < 64; i++)
text[i] = alf[rand() % alfl];
If you use text like a string, it must be '\0' terminated:
text[63] = '\0';