Why do need documents?

Answer 1

The best way I can explain this is to give you an example of code with no documentation. If there was documentation, you would be able to tell what this code did in a matter of seconds. Without it you could waste many minutes, or even hours, trying to understand it.

inline unsigned char f_1(const unsigned char *ptr, const unsigned int i) {

const div_t d = div(i, 8);

return (ptr[d.quot] & (1 << d.rem))?1:0;

}

inline void f_2(unsigned char *ptr, const unsigned int i) {

const div_t d = div(i, 8);

ptr += d.quot;

*ptr = *ptr | (1 << d.rem);

}

inline void f_3(unsigned char *ptr, const unsigned int i) {

const div_t d = div(i, 8);

const unsigned char n = 1 << d.rem;

ptr += d.quot;

*ptr = ((*ptr | n ) ^ n);

}

void f(const unsigned int n) {

const unsigned int m = n + (n%8==0?0:8-n%8);

const unsigned int n = m / 8;

const unsigned int m_2 = m / 2;

unsigned int i, j;

unsigned char *a = malloc(sizeof(unsigned char) * n);

memset(a, 0xaa, n);

f_3(a, 1);

f_2(a, 2);

for( i = 3; i < m_2; i+=2 ) {

while(i < m_2 && !f_1(a, i))

i+=2;

for( j = i + i; j < m; j+=i )

f_3(a, j);

}

free(a);

}