#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <conio.h>
void quick_sort(char* txt, int size)
{
int j = size -1 ;
int k = 0;
int c = txt[(int)(size / 2)];
int tmp = 0;
do
{
 while (txt[k] < c)k++;
 while (txt[size] < c)size--;
 if (k <= size) {
  tmp = txt[k];
  txt[k] = txt[size];
   txt[size] = tmp;
   k ++;
   size--;
 }
}
while (k <= size);
if (size > 0)quick_sort(txt, size);
if (j > 0)quick_sort(txt + k, j - k);
//for (int i = 0; i < size; ++i) {
 //printf("%d ", txt[i]);
//}
}
int main()
{
char *txt;
int size = 0;
int t = time(0);
srand(t);
printf("Enter size of mass: ");
if (scanf("%d", &size) != 1)
{
 printf("Input Error");
 _getch();
 return 0;
}
txt = (char*)malloc((size + 1) * sizeof(char));
if (!txt)
{
 printf("Can't alloc memory!\n");
 return 1;
}
memset(txt, 0, (size + 1) * sizeof(char));
for (int i = 0; i < (size); i++)
{
 int r = rand();
 char c = (r % 78) + 48;
 txt[i] = c;
}
//printf("%d \n", txt);
printf("no sorted: \n");
for (int i = 0; i < size; ++i) {
 printf("%d ", txt[i]);
}

quick_sort(txt, size);
printf("\n sorted: \n");
for (int i = 0; i < size; ++i) {
 printf("%d ", txt[i]);
}
free(txt);
_getch();
return 0;

}

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <conio.h>
void quick_sort(char* txt, int size)
{
int j = size -1 ;
int k = 0;
int c = txt[(int)(size / 2)];
int tmp = 0;
do
{
 while (txt[k] < c)k++;
 while (txt[size] < c)size--;
 if (k <= size) {
  tmp = txt[k];
  txt[k] = txt[size];
   txt[size] = tmp;
   k ++;
   size--;
 }
}
while (k <= size);
if (size > 0)quick_sort(txt, size);
if (j > 0)quick_sort(txt + k, j - k);
//for (int i = 0; i < size; ++i) {
 //printf("%d ", txt[i]);
//}
}
int main()
{
char *txt;
int size = 0;
int t = time(0);
srand(t);
printf("Enter size of mass: ");
if (scanf("%d", &size) != 1)
{
 printf("Input Error");
 _getch();
 return 0;
}
txt = (char*)malloc((size + 1) * sizeof(char));
if (!txt)
{
 printf("Can't alloc memory!\n");
 return 1;
}
memset(txt, 0, (size + 1) * sizeof(char));
for (int i = 0; i < (size); i++)
{
 int r = rand();
 char c = (r % 78) + 48;
 txt[i] = c;
}
//printf("%d \n", txt);
printf("no sorted: \n");
for (int i = 0; i < size; ++i) {
 printf("%d ", txt[i]);
}

quick_sort(txt, size);
printf("\n sorted: \n");
for (int i = 0; i < size; ++i) {
 printf("%d ", txt[i]);
}
free(txt);
_getch();
return 0;

}

Бо квік сорт кривий

что именно не так?

у gcc почти все реализовано, кроме:

 __VA_OPT__

(частично)
Immediate functions (частично)
Coroutines (частично)
DR: Array size deduction in new-expressions
Modules
using enum
DR: Implicit move for more local objects and rvalue references

Extending std::make_shared() to support arrays 
Synchronized buffered ostream
Atomic std::shared_ptr and std::weak_ptr
Calendar and timezone
Comparing unordered containers 
std::basic_string::reserve() should not shrink 
std::bit_cast()
Add shift to <algorithm>
Fixing operator>>(basic_istream&, CharT*)
The One Ranges Proposal
Heterogeneous lookup for unordered containers 
Efficient access to std::basic_stringbuf’s Buffer 
Layout-compatibility and pointer-interconvertibility traits 
Text formatting
constexpr std::string
constexpr std::vector
Input range adaptors
Atomic waiting and notifying, std::counting_semaphore, std::latch and std::barrier

Adding <=> to the standard library

ну ничего такаого ахуенного как rvalue или constexpr, что на уровень улучшит или упростит ежедневную работу нету(