While 'C' programmers are often creative visionaries who craft elegant, functional code... we are also - sadly - bug exterminators. One source of bugs is when a variable's OVERFLOW or UNDERFLOW can give rise to aberrant program behavior. Let's be clear on where the flow goes.
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A new feature has been added to past & present articles, to download source code rather than use copy and paste into your text editor. You'll need to use a different convention with 'goc' compile script: "./goc pgm30_main.c pgm30" |
/* pgm30 source */
#include <stdio.h>
int main(void) {
char ns_char; // no-sign, all char = 8 bits / 1 byte
signed char s_char; // signed -128 to 0 to +127
unsigned char us_char; // unsigned 0 to 255
short ns_short; // no-sign, all short = 16 bits / 2 bytes
signed short s_short; // signed -32768 to +32767
unsigned short us_short; // unsigned 0 to 65535
int ns_int; // no-sign, all int = 32 bits / 4 bytes
signed int s_int; // signed -2147483648 to +2147483647
unsigned int us_int; // unsigned 0 to 4294967295
printf("\n");
ns_char = s_char = 127; us_char = 255;
printf("--- 1 byte, 8 bits ---\n");
printf("(upper limit) ns_char: %+d, s_char: %+d, us_char: %u\n", ns_char, s_char, us_char);
ns_char++; s_char++; us_char++;
printf("(increment) ns_char: %+d, s_char: %+d, us_char: %u\n", ns_char, s_char, us_char);
ns_char++; s_char++; us_char++;
printf("(increment) ns_char: %+d, s_char: %+d, us_char: %u\n\n", ns_char, s_char, us_char);
ns_char = s_char = -128; us_char = 0;
printf("(lower limit) ns_char: %+d, s_char: %+d, us_char: %u\n", ns_char, s_char, us_char);
ns_char--; s_char--; us_char--;
printf("(decrement) ns_char: %+d, s_char: %+d, us_char: %u\n", ns_char, s_char, us_char);
ns_char--; s_char--; us_char--;
printf("(decrement) ns_char: %+d, s_char: %+d, us_char: %u\n\n", ns_char, s_char, us_char);
/* ******************** */
ns_short = s_short = 32767; us_short = 65535;
printf("--- 2 bytes, 16 bits ---\n");
printf("(upper limit) ns_short: %+d, s_short: %+d, us_short: %u\n", ns_short, s_short, us_short);
ns_short++; s_short++; us_short++;
printf("(increment) ns_short: %+d, s_short: %+d, us_short: %u\n", ns_short, s_short, us_short);
ns_short++; s_short++; us_short++;
printf("(increment) ns_short: %+d, s_short: %+d, us_short: %u\n\n", ns_short, s_short, us_short);
ns_short = s_short = -32768; us_short = 0;
printf("(lower limit) ns_short: %+d, s_short: %+d, us_short: %u\n", ns_short, s_short, us_short);
ns_short--; s_short--; us_short--;
printf("(decrement) ns_short: %+d, s_short: %+d, us_short: %u\n", ns_short, s_short, us_short);
ns_short--; s_short--; us_short--;
printf("(decrement) ns_short: %+d, s_short: %+d, us_short: %u\n\n", ns_short, s_short, us_short);
/* ******************** */
ns_int = s_int = 2147483647; us_int = 4294967295;
printf("--- 4 bytes, 32 bits ---\n");
printf("(upper limit) ns_int: %+d, s_int: %+d, us_int: %u\n", ns_int, s_int, us_int);
ns_int++; s_int++; us_int++;
printf("(increment) ns_int: %+d, s_int: %+d, us_int: %u\n", ns_int, s_int, us_int);
ns_int++; s_int++; us_int++;
printf("(increment) ns_int: %+d, s_int: %+d, us_int: %u\n\n", ns_int, s_int, us_int);
ns_int = s_int = -2147483648; us_int = 0;
printf("(lower limit) ns_int: %+d, s_int: %+d, us_int: %u\n", ns_int, s_int, us_int);
ns_int--; s_int--; us_int--;
printf("(decrement) ns_int: %+d, s_int: %+d, us_int: %u\n", ns_int, s_int, us_int);
ns_int--; s_int--; us_int--;
printf("(decrement) ns_int: %+d, s_int: %+d, us_int: %u\n", ns_int, s_int, us_int);
printf("\n");
return(0);
}
