Why is my print function giving the wrong output in my program to print strings?

Question

The expected outcome is for example:

a
word
a sentence

This is the outcome tho:

 aword
word
a sentence

Here's the code:

#include <stdlib.h>
#include <stdio.h>
    
int main() {
    char letter[1], word[20], sentence[100];  
    
    scanf("%s", letter);
    
    scanf("%s", word);
    
    scanf(" %[^\n]s", sentence);
    
    printf("\n %s", letter);
    printf("\n %s", word);
    printf("\n %s", sentence);
    
    return 0;
} 

Answer 1

At least these problems

No width limit

Never use scanf() to read user input into a string lacking a width in the format. The width should be less than the array count.

char letter[1],word[20],sentence[100];  
// scanf("%s", letter);
// scanf("%s", word);
// scanf(" %[^\n]s", sentence);
scanf("%0s", letter);          // "%0s" not valid.  See below
scanf("%19s", word);
scanf(" %99[^\n]s", sentence); // See below also

Buffer too small for "%s"

char letter[1] only big enough for a null string "". To read 1 character into a string, increase size

char letter[2];  
scanf("%1s", letter);

s not needed

s serves no point in " %[^\n]s". Who or whatever text suggested an s is a poor source of coding in C practice.

// scanf(" %99[^\n]s", sentence);
scanf(" %99[^\n]", sentence);

Check return value

Test the return value from all scanf().

// scanf("%1s", letter);
if (scanf("%1s", letter) != 1) {
  fprintf(stderr, "Failed to read into letter");
  return EXIT_FAILURE;
}