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#include <stdio.h>
#include <limits.h>
#include <float.h>
/* The C Programming Language, 2nd Edition
*
* Exercise 2-1: Write a program to determine the ranges of char, short,
* int, and long variables, both signed and unsigned, by printing
* appropriate values from standard headers and by direct computation.
* Harder if you compute them: determine the ranges of the various
* floating-point types.
*
* Answer: The trick to computing these numbers is to understand computer math,
* which is done in binary, thus with 2. Keep squaring from 1 and you'll
* eventually find the limit of the variable. Add or subtract from one of the
* extremes and you'll find the other extreme.
*
*/
int main() {
unsigned char uc;
signed char sc;
unsigned short us;
signed short ss;
unsigned int ui;
signed int si;
unsigned long ul;
signed long sl;
unsigned long long ull;
signed long long sll;
float fl, fla, fll;
double db, dba, dbl;
long double ldb, ldba, ldbl;
printf("Let's compute the minimums and maximums of each type!\n");
uc = sc = us = ss = ui = si = ul = sl = sll = ull = 0;
fl = fla = fll = db = dba = dbl = ldb = ldba = ldbl = 0.0;
/* Characters */
sc++;
while (sc * 2 > sc) {
sc = sc * 2 + 1;
}
printf("`signed char` maximum: %d\n", sc);
sc++;
printf("`signed char` minimum: %d\n", sc);
uc--;
printf("`unsigned char` maximum: %u\n", uc);
/* Short ints */
ss++;
while (ss * 2 > ss) {
ss = ss * 2 + 1;
}
printf("`signed short` maximum: %d\n", ss);
ss++;
printf("`signed short` minimum: %d\n", ss);
us--;
printf("`unsigned short` maximum: %u\n", us);
/* Integers */
si++;
while (si * 2 > si) {
si = si * 2 + 1;
}
printf("`signed int` maximum: %d\n", si);
si++;
printf("`signed int` minimum: %d\n", si);
ui--;
printf("`unsigned int` maximum: %u\n", ui);
/* Long ints */
sl++;
while (sl * 2 > sl) {
sl = sl * 2 + 1;
}
printf("`signed long` maximum: %li\n", sl);
sl++;
printf("`signed long` minimum: %li\n", sl);
ul--;
printf("`unsigned long` maximum: %lu\n", ul);
/* Long long ints */
sll++;
while (sll * 2 > sll) {
sll = sll * 2 + 1;
}
printf("`signed long long` maximum: %lli\n", sll);
sll++;
printf("`signed long long` minimum: %lli\n", sll);
ull--;
printf("`unsigned long long` maximum: %llu\n", ull);
/* Floats */
while (fl == 0.0) {
fll = fla;
fla = fla + 1111e28;
fl = (fl + fla) - fla;
}
printf("`float` maximum: %e\n", fll);
fl = 0.0;
fll = 0.0;
fla = 0.0;
while (fl == 0.0) {
fll = fla;
fla = fla - 1111e28;
fl = (fl - fla) + fla;
}
printf("`float` minimum: %e\n", fll);
/* Doubles */
while (db == 0.0) {
dbl = dba;
dba = dba + 1111e297;
db = (db + dba) - dba;
}
printf("`float` maximum: %e\n", dbl);
printf("`float` minimum: -%e\n", dbl);
printf("\nNow, let's cheat and use the helpful headers!\n");
printf("`char`s go from %d to %d (unsigned, up to %u)\n", SCHAR_MIN, SCHAR_MAX, UCHAR_MAX);
printf("`short`s go from %d to %d (unsigned, up to %u)\n", SHRT_MIN, SHRT_MAX, USHRT_MAX);
printf("`int`s go from %d to %d (unsigned, up to %u)\n", INT_MIN, INT_MAX, UINT_MAX);
printf("`long`s go from %ld to %ld (unsigned, up to %lu)\n", LONG_MIN, LONG_MAX, ULONG_MAX);
printf("`float`s range from %e to %e\n", FLT_MIN, FLT_MAX);
printf("`double`s range from %e to %e\n", DBL_MIN, DBL_MAX);
return 0;
}
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