程序语言中 tmp ans len beg 是什么意思？

如果可以请加我Q

#include <stdio.h>
#include <stdlib.h>

inline void Swap(int* lhs, int* rhs)
{
int tmp = *lhs;
*lhs = *rhs;
*rhs = tmp;
}

void Reverse(int* beg, int* end)
{
while(beg < end)
Swap(beg++, --end);
}

void Print(int* beg, int* end)
{
while(beg != end)
printf("%d ", *beg++);
putchar('\n');
}

inline int Cmp(const void* lhs, const void* rhs)
{
return *(const int*)rhs - *(const int*)lhs;
}

void Permutation(int* beg, int* mid, int* end)
{
if(end- mid > 1)
qsort(mid, end - mid, sizeof(int), Cmp);
int* nav = end - 1;
Print(beg, mid);

for(;;)
{
int* tmp = nav;
if(*--nav < *tmp)
{
int* rmbt = end;
while(*--rmbt <= *nav);
Swap(nav, rmbt);
if(tmp <= mid)
{
Reverse(tmp, end);
if(end - mid > 1)
qsort(mid, end - mid, sizeof(int), Cmp);
}
Print(beg, mid);
nav = end - 1;
}
if(nav == beg)
{
Reverse(beg, mid);
break;
}
}
}


int main()
{
int a[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
int m, n;

printf("Select n numbers\b\b\b\b\b\b\b\b\b");
scanf("%d", &n);
printf("from m numbers\b\b\b\b\b\b\b\b\b");
scanf("%d", &m);

Permutation(a, a + n, a + m);
}


Select 3 numbers
from 3 numbers
1 2 3
1 3 2
2 1 3
2 3 1
3 1 2
3 2 1


Select 2 numbers
from 3 numbers
1 2
1 3
2 1
2 3
3 1
3 2