CSCI 255 Data Types vol. 1

Integer data types of Java

• byte
  • 8-bit signed two's complement
  • Range: -128 to 127
• short
  • 16-bit signed two's complement
  • Range: -32768 to 32767
• int
  • 32-bit signed two's complement
  • Range: -2147483648 to 2147483647
• long
  • 64-bit signed two's complement
  • Range: -9223372036854775808 to 9223372036854775807

The char data type is designed for Unicode characters.

Integer data types of C

Quotes are from The C Programming Language by Kernighan and Ritchie.

ANSI C

• char
  • Can store "any member of the execution character set"
  • Can be signed or unsigined
    • The "plain" char may be either signed or unsigined
• int
  • Has the "natural size suggested by the host machine architecture"
  • Can be short or long
  • Can be signed or unsigined
    • The "plain" int is signed

Arithmetic with unsigned integers "obey the laws of arithmetic modulo 2ⁿ". Because signed integers are not required to be two's complement, many of their operations do not have a tight formal definition. For example, -5/2 could be either -2 or -3. If -5/2 is -2 then -5%2 must be -1, and if -5/2 is -3 then -5%2 must be 1; that is (-5/2)*2+5%2 must be 5.

The ANSI C standard requires that both the short int and the plain int be able to hold integers from -32767 to 32767 when signed and from 0 to 65535 when unsigned. The long int must be able to hold integers from -2147483647 to 2147483647 when signed and from 0 to 4294967295 when unsigned.

C99

The C99 standard includes a long long integer which is required to hold at least 64 bits.

Solutions through includes

• <limits.h>: defines constants, e.g., INT_MAX for minimum and maximum values
  • A program to print limits

    #include <limits.h>
    #include <stdio.h>
    
    int main(void) {
      printf("Largest char  is %d\n",  SCHAR_MAX) ;
      printf("Largest short is %d\n",  SHRT_MAX) ;
      printf("Largest int   is %d\n",  INT_MAX) ;
      printf("Largest long  is %ld\n", LONG_MAX) ;
      return 0 ;
    }
    

  • Run on a 32-bit computer

    Largest char  is 127
    Largest short is 32767
    Largest int   is 2147483647
    Largest long  is 2147483647
    

  • Run on a 64-bit computer

    Largest char  is 127
    Largest short is 32767
    Largest int   is 2147483647
    Largest long  is 9223372036854775807
    

• <stdint.h> in C99 and most recent C compilers: provides typedef's with size specific names, e.g., int32_t and uint16_t
• <pic24_generic.h> of the textbook: provides typedef's with size specific names, e.g., int32 and uint16