Check if char array has just '\0'

I'm trying to make some college stuff, and in this problem I have to make sure that a full name of a person is not all empty spaces like " " and does not have a number in it like "R4lph 123".
The number part I'm ok, but the empty spaces one is where I'm stuck.
It works if it's only one empty space, but if multiples, it spots working.

int checkName(char* name)
{
    if (name[0] == '
int checkName(char* name)
{
if (name[0] == '\0') //Checks if name starts with "space". If so, it's an invalid name.
return 1;
else
{
for (int i = 0; i < strlen(name); i++)
{
if (isdigit(name[i])) //Checks if there's a number in the name. If so, it's an invalid name.
return 1;
}
return 0;
}
}
') //Checks if name starts with "space". If so, it's an invalid name.
        return 1;
    else
    {
        for (int i = 0; i < strlen(name); i++)
        {
            if (isdigit(name[i])) //Checks if there's a number in the name. If so, it's an invalid name.
                return 1;
        }
        return 0;
    }
}

I've tried multiple functions like empty() and blank(), although I couldn't make black() work in my code.

Your idea was correct, but you did not check for space, but a different character. I have moved out the computation for the length of the string so we don't compute it in each iteration.

int checkName(char* name)
{
    if (name[0] == ' ') //Checks if name starts with "space". If so, it's an invalid name.
        return 1;
    else
    {
        int len = strlen(name);
        for (int i = 1; i < len; i++)
        {
            if (isdigit(name[i])) //Checks if there's a number in the name. If so, it's an invalid name.
                return 1;
        }
        return 0;
    }
}

Since C++ is tagged here your answer is in the string library, as @pm100 mentioned. The code posted is the C way of C++ programming, which is generally not desired. C++ offers many libraries that will help you 90% of the time.

I changed the prototype so gets a const std::string as a parameter, and made its return type bool. You can change that back to int and remove std::boolalpha in main().

I don't know your professor's requirements since you haven't listed any, so feel free to do anything you want with this code (using a char array vs a string).

The function uses a range-based for-loop to iterate over the string and check if each character is either a digit or a space, if it finds one it throws a runtime error. I used a try-catch block to handle them gracefully but it might be deemed unnecessary. The function returns false if the name is invalid and vice versa.

#include <iostream>
#include <string>
#include <stdexcept>

bool checkName(const std::string name) {
    try {
        for (auto letter : name) {
            if (letter == ' ') {
                throw std::runtime_error("[invalid name]");
            } else if (isdigit(letter)) {
                throw std::runtime_error("[invalid name]");
            }
        }
    } catch (std::exception& e) {
        std::cout << "{error}: " << e.what() << std::endl;
        return false;
    }
    return true;
}

int main() {
    const std::string name1 = "John";
    const std::string name2 = "Jo hn";
    const std::string name3 = "Jo3hn";

    std::cout << std::boolalpha << checkName(name1) << "\n";
    std::cout << std::boolalpha << checkName(name2) << "\n";
    std::cout << std::boolalpha << checkName(name3) << "\n";

    return 0;
}

If the the name must contains only alphabetic character, you can itereate through the string using the isalpha method - which check if a given char is an alhpabetic letter or not.

The loop will end when:

1. it reaches the end of the string because it contains only valid character;

2. the string contains a non-valid character.

   int checkName(const char* name)
   {
       int number_char = strlen(name);
       if(number_char==0) return 1;
       int index=0;
       while(isalpha(name[index]) && index<number_char) index++;
       return (index==number_char?0:1);
   }
   

In current C++, without pointers, the code would look like this:

#include <cctype>
#include <cassert>
#include <string_view>

// if something can have only two values consider using bool
// string_view accepts a lot of string types
// and we can use a view since we are only checking a string
bool checkName(const std::string_view name)
{
    if (name.size() != 0ul)
    {
        // range based for loop cannot go out of scope
        for (const auto c : name)
        {
            if (std::isdigit(c))
            {
                return true;
            }
        }
    }

    return false;
}

int main()
{
    auto nok = checkName("");
    assert(!nok);

    auto ok = checkName("hello1");
    assert(ok);

    return 0;
}

Assuming you use C++, null-terminated character arrays are relics from C legacy. We try to avoid them where possible. Alternatives are std::string for flexible strings and std::string_view for referencing immutable strings. In your example, the later is better. Next thing is to use std::isalfha instead of std::isdigit, because that's what you need. I am going extremely modern, using C++20:

#include <ranges>
#include <cctype>
#include <string_view>

bool checkName(const std::string_view name){
   constexpr auto to_uint = [](auto c)
   {return static_cast<uint8_t>(c);};
   if (auto space=std::ranges::count_if(name, std::isspace, to_uint); (space > 2) || (space == 0) )
       return false;
   return (std::ranges::end(name) ==
           std::ranges::find_if_not(name, [](auto c)
              { return std::isalpha(c)||std::isspace(c); }, to_uint);
};

assert((checkName("xxx yyy zzz")));

This function checks if the input string has one or two spaces(corresponding to first+[middle+]last name). Then if a none-alphabetic character is found, returns false. to_uint is a projection function used to prevent surprises due to integer promotions.
The problem with this implementation is that it cannot detect two consecutive spases, or empty input strings. That can also be solved by further complications that I did not try to include.