size_t my_strlen(const char *s) {
    const char* cur = s;
    for (; *cur; ++cur);
    return cur - s;
}

int size_s(char *s)
{
    int i;
    for (i = 0; s[i] != ''; i++);
    return i;
}

#include <stdio.h>

int main(int argc, char *argv[]){
  int i = 1;
  for(;i<argc;i++){
    char *pStr = argv[i];
    int length = 0;
    while(*pStr++ != ''){
      length++;
    }
    printf("%dn", length);
  }
}

gcc main.c

./a.out some_string

size_t strlen(const char *s) {
    const char *p;
    for (p = s; *p; ++p);
    return p - s;
}

xor eax, eax
mov ecx, -1
mov edi, some_string
mov ebx, edi
cld
push ds
pop es
repne scasb
mov eax, edi
sub eax, ebx
dec eax

size_t strlen( const char *s )
{
  const char *p = s;

  for (;;)
  {
    uint32 c = *((uint32*)p);

    if ( (c - 0x01010101u) & 0x80808080u )
    {
      if ((c & 0x000000ffu) == 0) return p-s+0;
      if ((c & 0x0000ff00u) == 0) return p-s+1;
      if ((c & 0x00ff0000u) == 0) return p-s+2;
      if ((c & 0xff000000u) == 0) return p-s+3;
    }
    p += 4;
  }
}

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

int number(string chislosimvolov, int i);

int  main()
{
string chisla;
int i;
cout << "nEnter stroky:";
cin >> chisla;
cout << "Number of symbols in it is: "<< number(chisla, int (chisla.size()));
 }

int number(string chislosimvolov, int i)
{
    int t;
    if (i== -1) t = 0;
    else
    t = number(chislo,i-1)
;
return t;
}