Print ABC - string [closed] - c

Question

Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 6 years ago.
Improve this question
My program need to print all the ABC but I see I have problems with the code. How I can fix it? (no pointer for this time).
What is the runtime error in the code and how to fix it?
Here is the code:
// Elvis’s hip and happening ABC-printing code
#include <stdio.h>
#include <string.h>
#define NUM_ABC_LET 26
void makeABC(char abc[NUM_ABC_LET]);
int main() {
char abcString[NUM_ABC_LET] = "";
makeABC(abcString);
puts(abcString);
return (0);
}
void makeABC(char abc[NUM_ABC_LET]) {
char letter;
for (letter = 'a'; letter <= 'z'; letter++) {
strcat(abc, letter);
}
}

Answer 1

The problem is that the strcat function expects both arguments to be (zero-terminated) strings. You only pass one string, and then one single character as arguments (which should give you compiler warnings).
You need to convert this single characters into a string (or an array) of a single character.
And don't forget that strings in C are zero-terminated.
What happens you use the single character as argument to the strcat function is that the compiler converts it to an int which is then in turn converted to a pointer. The problem with this is that the address 'a' (for example) is not a valid address to a string. That will lead to undefined behavior and a crash.

Answer 2

Your program logic is correct, the problem is the calling of the strcat() function. The strcat() function is implemented as:
char *strcat(char *dest, const char *src)
{
char *ret = dest;
while (*dest)
dest++;
while (*dest++ = *src++);
return ret;
}
The second argument must be a string instead which you pass a character.
This is the reason for your run time error.

Answer 3

Can you try something like following? I haven't tested the following but it should work on most part.
// Elvis’s hip and happening ABC-printing code
#include <stdio.h>
#include <string.h>
#define NUM_ABC_LET 26
void makeABC(char abc[NUM_ABC_LET]);
int main()
{
char abcString[NUM_ABC_LET + 1];
makeABC(abcString);
puts(abcString);
return 0;
}
void makeABC(char abc[NUM_ABC_LET + 1])
{
char letter;
int i=0;
for(letter = 'a'; letter <= 'z'; letter++)
{
abc[i] = letter;
i++;
}
abc[i]='\0';
}

Answer 4

Your program has several issues:
You cannot call strcat with a char, you must pass char * arguments, pointing to null terminated C strings.
The array into which you compose the alphabet is too short: you need to define it with a size one larger than the number of characters for the final '\0' terminator.
Here is a corrected version:
#include <stdio.h>
#include <string.h>
#define NUM_ABC_LET ('z' - 'a' + 1) // 26 ASCII letters
void makeABC(char *abc); // makeABC receives a pointer to an array of char
// this declaration is equivalent to
// void makeABC(char abc[NUM_ABC_LET+1]);
// but less error prone
int main(void) {
char abcString[NUM_ABC_LET + 1] = "";
makeABC(abcString);
puts(abcString);
return 0;
}
void makeABC(char *abc) {
char letter;
char buf[2]; // a buffer for a 1 letter C string
for (letter = 'a'; letter <= 'z'; letter++) {
buf[0] = letter; // make a 1 letter string
buf[1] = '\0'; // set the null terminator
strcat(abc, buf);
}
}

Answer 5

Prototype of strcat is
char *strcat(char *destination, const char *source);
means our source as well as destinations should and must be string so this is the issue that why if you compile in turbo c it will through error of
"type mismatch".
and if you wanna write program for printing ABC up to Z than simply write
void main()
{
int i;
for(i = 65; i<=90; i++)
{
printf("%c", i);
}
}
I hope you will like it......

Answer 6

As a slight variation, I would suggest passing the length of the character array to the function, so that the function does not overflow the array.
As the character array is passed to the function as a pointer, the function does not know it's size.
In your case you know the size, but for the future it might be better to explicitly pass the size.
Also I just copied the characters rather than use strcat, and added the null termination at the end.
#include <stdio.h>
#define NUM_ABC_LET 26
/* function takes pointer to array and size of array */
void makeABC(char *abc, int len);
int main()
{
/* array needs to include space for null termination */
char abcString[NUM_ABC_LET + 1];
/* call function with pointer + size */
makeABC(abcString, NUM_ABC_LET);
printf("%s\n", abcString);
return (0);
}
void makeABC(char *abc, int len)
{
int n;
for(n = 0; n < len; n++ ) {
/* add letters to the array */
abc[n] = n + 'a';
}
/* put a null termination on the end */
abc[n] = '\0';
}