I am trying to add two strings together but getting 3221225477 Error

Question

I am trying to get a number and a repetition number then adding as many numbers as the number of repetition one after the other. But I am getting 3221225477 result. What should I do?

The function:

char *repetitor(char number[], int repFactor){
char* temp;
while(repFactor>0){
    strcat(temp, number);
    repFactor--;
}
return temp;

The main function:

int main(int argc, char *argv[]) {
char* number;
int repFactor = 0;
printf("Please enter a number (n=) :");
scanf("%s", &number);
printf("Please enter repetition factor (k=) :");
scanf("%d", &repFactor);

char* numberRep = (repetitor(number,repFactor));

Answer 1

Lots of issues here:

scanf("%s", &number); reads stdin and stores input in a buffer pointed to by the second argument. number is not the expected buffer, it's a pointer, so you're passing the address of a pointer (char **) to scanf(). number is sizeof(char *) bytes big, so you can get away with entering a character or three, but number should be an array of characters:

char number[100]; … scanf("%s", number); // no check for overflow!

Re: repetitor(), not only is temp uninitialized (you're copying to random space and strcat() needs find a trailing NUL), there's no buffer space allocated, and you're returning a stack variable that no longer exists when repetitor() returns.

When you're learning, turn on ALL your compiler warnings.