Program to determine ranges of char, short, int and long variables, both signed and unsigned

Question

I wrote code to determinate ranges of char,short int and long variables,both signed and unsigned.Please help me to improve my code :) Here is the code:

#include <stdio.h>
//function declerations...
long power(int base, int power);
int main(void) {
 //From 2^(N-1) to 2^(N-1)-1 (Two's complement)
 int intmin = power(2, sizeof(int) * 8 - 1);
 int intmax = power(2, sizeof(int) * 8 - 1) - 1;
 unsigned unsignedintmax = power(2, sizeof(int) * 8) - 1;
 char minchar = -(power(2, sizeof(char) * 8 - 1));
 char maxchar = power(2, sizeof(char) * 8 - 1) - 1;
 unsigned char unsignedcharmax = power(2, sizeof(char) * 8) - 1;
 short shortmin = -(power(2, sizeof(short) * 8 - 1));
 short shortmax = power(2, sizeof(short) * 8 - 1) - 1;
 unsigned short unsignedshortmax = power(2, sizeof(short) * 8) - 1;
 long minlong = power(2, sizeof(long) * 8 - 1);
 long maxlong = power(2, sizeof(long) * 8 - 1) - 1;
 unsigned long unsignedlongmax = power(2, sizeof(long) * 8) - 1;
 minlong*=-1;
 printf("\nSigned char can be minimum: %d and maximum: %d\n", minchar, maxchar);
 printf("\nUnsigned char can be minimum: %d and maximum: %u\n", 0, unsignedcharmax);
 printf("\nSigned short can be minimum: %d and maximum: %d\n", shortmin, shortmax);
 printf("\nUnsigned short can be minimum: %d and maximum: %u\n", 0, unsignedshortmax);
 printf("\nSigned int can be minimum: %d and maximum: %d\n", intmin, intmax);
 printf("\nUnsigned int can be minimum: %d and maximum: %u\n", 0, unsignedintmax);
 printf("\nSigned long can be minimum: %ld and maximum: %ld\n", minlong, maxlong);
 printf("\nUnsigned long can be minimum: %d and maximum: %lu\n\n", 0, unsignedlongmax);
 return 0;
}
long power(int base, int power) {
 long pf = 1;
 for (int i = 0; i < power; i++) {
 pf *= base;
 }
 return pf;
}

Answer 1

• Signedness of unqualified char is implementation defined. It may well be possible that char is in fact unsigned. Change char to signed char.

• A char is not guaranteed to have 8 bits (it is guaranteed to have at least 8 bits). Use CHAR_BIT instead.

• Narrowing types (e.g. assigning long to char) always make me uncomfortable. A better technique to get a value with only MSB set is (TYPE is either char,int,long,whatever)

  unsigned TYPE value = ~(((unsigned TYPE) -1) >> 1)
  

• Silidrone: I just don't understand why is char not guaranteed to be 8 bits.Because as i know it must be 8 bits.Please correct me if i am wrong.
• Incomputable: @MuhamedCicak, you're wrong. Wikipedia hosted small reference page for your question.
• pm100: i have worked on computers where char is 7 bits, where null is 0xffffffff. C deals with all sorts of types of machine
• Silidrone: Than how ASCII Code works ?? I mean its not 255 but 127 ??
• vnp: @MuhamedCicak Check this: stackoverflow.com/questions/2098149/…