Cstring problems

[JBIRD304]

I am having trouble getting this program to work can someone show me what I am doing wrong?

Design, code, and test a function that accepts a pointer to a C-string as an argument – the function computes and returns the number of characters in the string. In the driver program prompt the user to input a string, pass the string to the function, and then display the function return value with an appropriate message.

// strLen() accepts a pointer to a C-string and returns the number of
// characters in the string
int strLen(char * s);

const int SIZE = 81; // size of char array

/* Sample output:
Enter a phrase of up to 80 characters:
sooner or later one of us must know if you just did what you're supposed to do

That phrase contains 78 characters */



This is the code I have written.

#include <iostream>
#include <cctype>
using namespace std;

 // strLen() accepts a pointer to a C-string and returns the number of 
 //  characters in the  string
int strLen(char  *s);

const int SIZE = 81;	// size of char array

int main()
{
	
	char *string;
	int count;

	cout << "Enter a phrase up to 80 characters: " << endl;
	cin >> *string;

	count = strLen(string);
	
	cout << "The number of characters in this string is: " << count;

	return 0;


}

int strLen(char  *s)
{
	int count = 0;
	int k = 0;

	while(s[k] != '\0')
	{
		count++;
		k++;
	}

	return count;
	

[pogrady]

consider std::cin.get(char*, streamsize n).

http://www.cplusplus.com/reference/istream/istream/get/

#include <iostream>  //for cin
#include <ios>           //for streamsize
#include <limits>       //for limits

//...

char* string;

cin.get(string, std::numeric_limits<std::streamsize>::max());

[Imadatobanisa]

1-

char *string;

You defined a null pointer (it is not allocated). If you access it, it will cause crash the program at all.

So, how to solve it :
char string[SIZE]; char *string = new char[SIZE]; //Remember to free memory

2-

count = strLen(string);

Making a function is very good IMO. :) Similar function :
count = strlen(string);// strLen ? different

Edit :

3-

cin >> *string;

How to solve it :
cin >> string;

You should not attach a string pointer (Because a pointer is an address, that means "cin >> (int)")

[maeriden]

Arrays and pointers are very similar but not the same.

Arrays have a size because the memory for them is automatically allocated.
Pointers are assigned either to an existing variable or to dynamically allocated memory.

You defined a pointer but did neither of the two above, so 'string' is uninitialized and points to an invalid memory address for which you don't have read/write permission. Any operation involving data in that address will cause the program to crash

To fix you can either define an array (which is what I suppose your assignment wants) or dynamically allocate memory for that pointer with new.

Another problem is that the extraction operator >> stops reading at the first whitespace, so it will only read up to "sooner". Like pogrady suggested cin.get() is a good solution
but it will not automatically put a '\0' at the end of the string. I think cin.getline() does that though I didn't read well

Note
cin >> *string;
Since 'string' is a pointer to char, '*string' is a char. Doing that makes the program call the extraction operator for chars, which reads a single character from the stream